Article 517

Health Care Facilities

Informational Note: Text that is followed by a reference in brackets has been extracted from NFPA 99 -2015, Health Care Facilities Code, and NFPA 101-2015, Life Safety Code. Only editorial changes were made to the extracted text to make it consistent with this Code.

Part I. General

Scope. The provisions of this article shall apply to elec‐ trical construction and installation criteria in health care facili‐ ties that provide services to human beings.The requirements in Parts II and III not only apply to single- function buildings but are also intended to be individually applied to their respective forms of occupancy within a multi‐ function building (e.g., a doctor’s examining room located within a limited care facility would be required to meet the provisions of 517.10).Informational Note: For information concerning performance, maintenance, and testing criteria, refer to the appropriate health care facilities documents.
Definitions.

Alternate Power Source. One or more generator sets, or battery systems where permitted, intended to provide power during the interruption of the normal electrical service; or the public utility electrical service intended to provide power during interruption of service normally provided by the gener‐ ating facilities on the premises. [99:3.3.4]

patients that provides, on an outpatient basis, one or more of the following:

Treatment for patients that renders the patients incapa‐ ble of taking action for self-preservation under emer‐ gency conditions without assistance of others.
Anesthesia that renders the patients incapable of taking action for self-preservation under emergency conditions without the assistance of others.
Emergency or urgent care for patients who, due to the nature of their injury or illness, are incapable of taking action for self-preservation under emergency conditions without the assistance of others. [101: 3.3.188.1]

Anesthetizing Location. Any area of a facility that has been designated to be used for the administration of any flammable or nonflammable inhalation anesthetic agent in the course of examination or treatment, including the use of such agents for relative analgesia.

Battery-Powered Lighting Units. Individual unit equipment for backup illumination consisting of the following:

Rechargeable battery
Battery-charging means
Provisions for one or more lamps mounted on the equip‐ ment, or with terminals for remote lamps, or both
Relaying device arranged to energize the lamps automati‐ cally upon failure of the supply to the unit equipment

Critical Branch. A system of feeders and branch circuits supply‐ ing power for task illumination, fixed equipment, select recep‐ tacles, and select power circuits serving areas and functions related to patient care that are automatically connected to alternate power sources by one or more transfer switches during interruption of normal power source. [99:3.3.27]

Electrical Life-Support Equipment. Electrically powered equip‐

Ambulatory Health Care Occupancy.

used to

ment whose continuous operation is necessary to maintain a

An occupancy

provide services or treatment simultaneously to four or more

patient’s life. [99:3.3.39]

Equipment Branch. A system of feeders and branch circuits arranged for delayed, automatic, or manual connection to the alternate power source and that serves primarily 3-phase power equipment. [99:3.3.43].

Essential Electrical System. A system comprised of alternate sources of power and all connected distribution systems and ancillary equipment, designed to ensure continuity of electrical power to designated areas and functions of a health care facility during disruption of normal power sources, and also to mini‐ mize disruption within the internal wiring system. [99:3.3.45]

Exposed Conductive Surfaces. Those surfaces that are capable of carrying electric current and that are unprotected, uninsula‐ ted, unenclosed, or unguarded, permitting personal contact. [99:3.3.47]

Informational Note: Paint, anodizing, and similar coatings are not considered suitable insulation, unless they are listed for such use.

Fault Hazard Current. See Hazard Current.

Flammable Anesthetics. Gases or vapors, such as fluroxene, cyclopropane, divinyl ether, ethyl chloride, ethyl ether, and ethylene, which may form flammable or explosive mixtures with air, oxygen, or reducing gases such as nitrous oxide.

Flammable Anesthetizing Location. Any area of the facility that has been designated to be used for the administration of any flammable inhalation anesthetic agents in the normal course of examination or treatment.

Governing Body. The person or persons who have the overall legal responsibility for the operation of a health care facility. [99:3.3.62]

Hazard Current. For a given set of connections in an isolated power system, the total current that would flow through a low impedance if it were connected between either isolated conductor and ground.

Fault Hazard Current. The hazard current of a given isolated system with all devices connected except the line isolation monitor.

Monitor Hazard Current. The hazard current of the line isola‐ tion monitor alone.

Total Hazard Current. The hazard current of a given isolated system with all devices, including the line isolation monitor, connected.

Health Care Facilities. Buildings, portions of buildings, or mobile enclosures in which human medical, dental, psychiatric, nursing, obstetrical, or surgical care are provided. [99:3.3.67]

Informational Note: Examples of health care facilities include, but are not limited to, hospitals, nursing homes, limited care facilities, clinics, medical and dental offices, and ambulatory care centers, whether permanent or movable.

Hospital. A building or portion thereof used on a 24-hour basis for the medical, psychiatric, obstetrical, or surgical care of four or more inpatients. [ 101: 3.3.142]

Isolated Power System. A system comprising an isolating trans‐ former or its equivalent, a line isolation monitor, and its ungrounded circuit conductors. [99:3.3.83]

Isolation Transformer. A transformer of the multiple-winding type, with the primary and secondary windings physically sepa‐

rated, that inductively couples its ungrounded secondary wind‐ ing(s) to the grounded feeder system that energizes its primary winding(s). [99:3.3.84]

Invasive Procedure. Any procedure that penetrates the protec‐ tive surfaces of a patient’s body (i.e., skin, mucous membrane, cornea) and that is performed with an aseptic field (procedural site). Not included in this category are placement of peripheral intravenous needles or catheters used to administer fluids and/or medications, gastrointestinal endoscopies (i.e., sigmoi‐ doscopies), insertion of urethral catheters, and other similar procedures. [99:3.3.81]

Life Safety Branch. A system of feeders and branch circuits supplying power for lighting, receptacles, and equipment essential for life safety that is automatically connected to alter‐ nate power sources by one or more transfer switches during interruption of the normal power source. [99:3.3.87]

Limited Care Facility. A building or portion thereof used on a 24-hour basis for the housing of four or more persons who are incapable of self-preservation because of age; physical limita‐ tion due to accident or illness; or limitations such as mental retardation/developmental disability, mental illness, or chemi‐ cal dependency.

Line Isolation Monitor. A test instrument designed to continu‐ ally check the balanced and unbalanced impedance from each line of an isolated circuit to ground and equipped with a built- in test circuit to exercise the alarm without adding to the leak‐ age current hazard. [99:3.3.89]

Medical Office (Dental Office). A building or part thereof in which the following occur: (1) examinations and minor treat‐ ments or procedures are performed under the continuous supervision of a medical or dental professional; (2) only seda‐ tion or local anesthesia is involved and treatment or proce‐ dures do not render the patient incapable of self-preservation under emergency conditions; and (3) overnight stays for patients or 24-hour operation are not provided. [99:3.3.98]

Monitor Hazard Current. See Hazard Current.

Nurses’ Stations. Areas intended to provide a center of nurs‐ ing activity for a group of nurses serving bed patients, where the patient calls are received, nurses are dispatched, nurses’ notes written, inpatient charts prepared, and medications prepared for distribution to patients. Where such activities are carried on in more than one location within a nursing unit, all such separate areas are considered a part of the nurses’ station.

Nursing Home. A building or portion of a building used on a 24-hour basis for the housing and nursing care of four or more persons who, because of mental or physical incapacity, might be unable to provide for their own needs and safety without the assistance of another person. [101: 3.3.142.2]

Patient Bed Location. The location of a patient sleeping bed, or the bed or procedure table of a critical care space. [99:3.3.125]

Patient Care Space. Any space of a health care facility wherein patients are intended to be examined or treated. [99:3.3.127]

Informational Note No. 1: The governing body of the facility

designates patient care space in accordance with the type of patient care anticipated. [99:1.3.4.1]

Informational Note No. 2: Business offices, corridors, lounges,

day rooms, dining rooms, or similar areas typically are not classi‐ fied as patient care spaces. [99:A.3.3.127]

Informational Note: [Category 3] spaces, formerly known as

basic care rooms [(spaces)], are typically where basic medical or dental care, treatment, or examinations are performed. Exam‐ ples include, but are not limited to, examination or treatment rooms in clinics, medical and dental offices, nursing homes, and limited care facilities. [99:A.3.3.127.3]

Basic Care (Category 3) Space. Space in which failure of equip‐ ment or a system is not likely to cause injury to the patients, staff, or visitors but can cause patient discomfort. [99:3.3.127.3]

General Care (Category 2) Space. Space in which failure of equip‐ ment or a system is likely to cause minor injury to patients, staff, or visitors. [99:3.3.127.2]

Informational Note: [Category 2] spaces were formerly known as general care rooms [(spaces)]. Examples include, but are not limited to, inpatient bedrooms, dialysis rooms, in vitro fertiliza‐ tion rooms, procedural rooms, and similar rooms. [99:A.3.3.127.2]

•

Critical Care (Category 1) Space. Space in which failure of equip‐

Informational Note: [Category 1] spaces, formerly known as crit‐

ical care rooms [(spaces)], are typically where patients are inten‐ ded to be subjected to invasive procedures and connected to line-operated, patient care–related appliances. Examples include, but are not limited to, special care patient rooms used for critical care, intensive care, and special care treatment rooms such as angiography laboratories, cardiac catheterization labora‐ tories, delivery rooms, operating rooms, post-anesthesia care units, trauma rooms, and other similar rooms. [99:A.3.3.127.1]

ment or a system is likely to cause major injury or death of patients, staff, or visitors. [99:3.3.127.1]

•

Support (Category 4) Space. Space in which failure of equipment

or a system is not likely to have a physical impact on patient care. [99:3.3.127.4]

Informational Note: [Category 4] spaces were formerly known as support rooms [(spaces)]. Examples of support spaces include, but are not limited to, anesthesia work rooms, sterile supply, laboratories, morgues, waiting rooms, utility rooms, and lounges. [99:A.3.3.127.4]

Patient Care Vicinity. A space, within a location intended for the examination and treatment of patients, extending 1.8 m (6 ft) beyond the normal location of the patient bed, chair, table, treadmill, or other device that supports the patient during examination and treatment and extending vertically to

2.3 m (7 ft 6 in.) above the floor. [99:3.3.128]

Patient Equipment Grounding Point. A jack or terminal that serves as the collection point for redundant grounding of elec‐ trical appliances serving a patient care vicinity or for grounding other items in order to eliminate electromagnetic interference problems. [99:3.3.129]

Psychiatric Hospital. A building used exclusively for the psychi‐ atric care, on a 24-hour basis, of four or more inpatients.

Reference Grounding Point. The ground bus of the panel‐ board or isolated power system panel supplying the patient care room. [99:3.3.143]

Relative Analgesia. A state of sedation and partial block of pain perception produced in a patient by the inhalation of concen‐ trations of nitrous oxide insufficient to produce loss of consciousness (conscious sedation).

Selected Receptacles. A minimum number of receptacles selected by the governing body of a facility as necessary to provide essential patient care and facility services during loss of normal power. [99:3.3.148]

Task Illumination. Provisions for the minimum lighting required to carry out necessary tasks in the described areas, including safe access to supplies and equipment and access to exits. [99:63.3.161]

Total Hazard Current. The hazard current of a given isolated system with all devices, including the line isolation monitor, connected. [99:3.3.66.3]

Wet Procedure Location. The area in a patient care space where a procedure is performed that is normally subject to wet conditions while patients are present, including standing fluids on the floor or drenching of the work area, either of which condition is intimate to the patient or staff. [99:3.3.171]

Informational Note: Routine housekeeping procedures and inci‐ dental spillage of liquids do not define a wet procedure loca‐ tion. [99:A.3.3.171]

X-Ray Installations, Long-Time Rating. A rating based on an operating interval of 5 minutes or longer.

X-Ray Installations, Mobile. X-ray equipment mounted on a permanent base with wheels, casters, or a combination of both to facilitate moving the equipment while completely assembled.

X-Ray Installations, Momentary Rating. A rating based on an operating interval that does not exceed 5 seconds.

X-Ray Installations, Portable. X-ray equipment designed to be hand carried.

X-Ray Installations, Transportable. X-ray equipment to be conveyed by a vehicle or that is readily disassembled for trans‐ port by a vehicle.

Part II. Wiring and Protection

Applicability.
1. Applicability. Part II shall apply to patient care space of all health care facilities.
2. Not Covered. Part II shall not apply to the following:
1. Business offices, corridors, waiting rooms, and the like in clinics, medical and dental offices, and outpatient facili‐ ties
2. Areas of nursing homes and limited care facilities wired in accordance with Chapters 1 through 4 of this Code where these areas are used exclusively as patient sleeping rooms
Informational Note: See NFPA 101 -2015, Life Safety Code ® .
General Installation — Construction Criteria. The purpose of this article is to specify the installation criteria and wiring methods that minimize electrical hazards by the mainte‐ nance of adequately low potential differences only between exposed conductive surfaces that are likely to become ener‐ gized and could be contacted by a patient.Informational Note: In a health care facility, it is difficult to prevent the occurrence of a conductive or capacitive path from the patient’s body to some grounded object, because that path may be established accidentally or through instrumentation
directly connected to the patient. Other electrically conductive surfaces that may make an additional contact with the patient, or instruments that may be connected to the patient, then become possible sources of electric currents that can traverse the patient’s body. The hazard is increased as more apparatus is associated with the patient, and, therefore, more intensive precautions are needed. Control of electric shock hazard requires the limitation of electric current that might flow in an electrical circuit involving the patient’s body by raising the resist‐ ance of the conductive circuit that includes the patient, or by insulating exposed surfaces that might become energized, in addition to reducing the potential difference that can appear between exposed conductive surfaces in the patient care vicinity, or by combinations of these methods. A special problem is presented by the patient with an externalized direct conductive path to the heart muscle. The patient may be electrocuted at current levels so low that additional protection in the design of appliances, insulation of the catheter, and control of medical practice is required.
Wiring Methods. Except as modified in this article, wiring methods shall comply with the applicable provisions of Chapters 1 through 4 of this Code.
Grounding of Receptacles and Fixed Electrical Equip‐ ment in Patient Care Spaces. Wiring in patient care spaces shall comply with 517.13(A) and (B).
1. Wiring Methods. All branch circuits serving patient care spaces shall be provided with an effective ground-fault current path by installation in a metal raceway system or a cable having a metallic armor or sheath assembly. The metal raceway system, metallic cable armor, or sheath assembly shall itself qualify as an equipment grounding conductor in accordance with 250.118.
2. Insulated Equipment Grounding Conductors and Insulated Equipment Bonding Jumpers.
  1. General. The following shall be directly connected to an insulated copper equipment grounding conductor that is clearly identified along its entire length by green insulation and installed with the branch circuit conductors in the wiring methods as provided in 517.13(A):
(1) The grounding terminals of all receptacles other than isolated ground receptacles(2) Metal outlet boxes, metal device boxes, or metal enclo‐sures(3) All non–current-carrying conductive surfaces of fixed electrical equipment likely to become energized that are subject to personal contact, operating at over 100 voltsException No. 1: For other than isolated ground receptacles, an insula‐ ted equipment bonding jumper that directly connects to the equipment grounding conductor is permitted to connect the box and receptacle(s) to the equipment grounding conductor. Isolated ground receptacles shall be connected in accordance with 517.16.Exception No. 2: Metal faceplates shall be permitted to be connected to the equipment grounding conductor by means of a metal mounting screw(s) securing the faceplate to a grounded outlet box or grounded wiring device.Exception No. 3: Luminaires more than 2.3 m (71∕2 ft) above the floor and switches located outside of the patient care vicinity shall be permit‐ ted to be connected to an equipment grounding return path complying with 517.13(A) or (B).(2) Sizing. Equipment grounding conductors and equipment bonding jumpers shall be sized in accordance with 250.122.
Panelboard Bonding. The equipment grounding terminal buses of the normal and essential branch-circuit panelboards serving the same individual patient care vicinity shall be connected together with an insulated continuous copper conductor not smaller than 10 AWG. Where two or more panelboards serving the same individual patient care vicinity are served from separate transfer switches on the essen‐ tial electrical system, the equipment grounding terminal buses of those panelboards shall be connected together with an insu‐ lated continuous copper conductor not smaller than 10 AWG. This conductor shall be permitted to be broken in order to terminate on the equipment grounding terminal bus in each panelboard.

Use of Isolated Ground Receptacles.
1. Inside of a Patient Care Vicinity. An isolated grounding receptacle shall not be installed within a patient care vicinity. [99:6.3.2.2.7.1(B)]
2. Outside of a Patient Care Vicinity. Isolated ground recep‐ tacle(s) installed in patient care spaces outside of a patient care vicinity(s) shall comply with 517.16(B)(1) and (2).N
  1. The grounding terminals of isolated ground receptacles installed in branch circuits for patient care spaces shall be connected to an insulated equipment grounding conductor in accordance with 250.146(D) in addition to the equipment grounding conductor path required in 517.13(A).The equipment grounding conductor connected to the grounding terminals of isolated ground receptacles in patient care spaces shall be clearly identified along the equipment grounding conductor’s entire length by green insulation with one or more yellow stripes.N
  2. The insulated grounding conductor required in 517.13(B)(1) shall be clearly identified along its entire length by green insulation, with no yellow stripes, and shall not be connected to the grounding terminals of isolated ground receptacles but shall be connected to the box or enclosure indi‐ cated in 517.13(B)(1)(2) and to non–current-carrying conduc‐ tive surfaces of fixed electrical equipment indicated in 517.13(B)(1)(3).
Informational Note No. 1: This type of installation is typically used where a reduction of electrical noise (electromagnetic interference) is necessary, and parallel grounding paths are to be avoided.Informational Note No. 2: Care should be taken in specifying a system containing isolated ground receptacles, because the grounding impedance is controlled only by the grounding wires and does not benefit from any conduit or building structure in parallel with the grounding path. [99:A.6.3.2.2.7.1]
Ground-Fault Protection.
1. Applicability. The requirements of 517.17 shall apply to hospitals, and other buildings (including multiple-occupancy buildings) with critical care (Category 1) spaces or utilizing electrical life-support equipment, and buildings that provide the required essential utilities or services for the operation of critical care (Category 1) spaces or electrical life-support equip‐ ment.
2. Feeders. Where ground-fault protection is provided for operation of the service disconnecting means or feeder discon‐ necting means as specified by 230.95 or 215.10, an additional step of ground-fault protection shall be provided in all next
  level feeder disconnecting means downstream toward the load. Such protection shall consist of overcurrent devices and current transformers or other equivalent protective equipment that shall cause the feeder disconnecting means to open.The additional levels of ground-fault protection shall not be installed on the load side of an essential electrical system trans‐ fer switch.
3. Selectivity. Ground-fault protection for operation of the service and feeder disconnecting means shall be fully selective such that the feeder device, but not the service device, shall open on ground faults on the load side of the feeder device. Separation of ground-fault protection time-current characteris‐ tics shall conform to manufacturer’s recommendations and shall consider all required tolerances and disconnect operating time to achieve 100 percent selectivity.Informational Note: See 230.95, informational note, for transfer of alternate source where ground-fault protection is applied.
4. Testing. When equipment ground-fault protection is first installed, each level shall be performance tested to ensure compliance with 517.17(C).
General Care (Category 2) Spaces.
1. Patient Bed Location. Each patient bed location shall be supplied by at least two branch circuits, one from the critical branch and one from the normal system. All branch circuits from the normal system shall originate in the same panelboard. The electrical receptacles or the cover plate for the electrical receptacles supplied from the critical branch shall have a distinctive color or marking so as to be readily identifiable and shall also indicate the panelboard and branch-circuit number supplying them.Branch circuits serving patient bed locations shall not be part of a multiwire branch circuit.Exception No. 1: Branch circuits serving only special purpose outlets or receptacles, such as portable X-ray outlets, shall not be required to be served from the same distribution panel or panels.Exception No. 2: The requirements of 517.18(A) shall not apply to patient bed locations in clinics, medical and dental offices, and outpa‐ tient facilities; psychiatric, substance abuse, and rehabilitation hospi‐ tals; sleeping rooms of nursing homes; and limited care facilities meeting the requirements of 517.10(B)(2).Exception No. 3: A general care (Category 2) patient bed location served from two separate transfer switches on the critical branch shall not be required to have circuits from the normal system.
2. Patient Bed Location Receptacles. Each patient bed loca‐ tion shall be provided with a minimum of eight receptacles. They shall be permitted to be of the single, duplex, or quadru‐ plex type or any combination of the three. All receptacles shall be listed “hospital grade” and shall be so identified. The grounding terminal of each receptacle shall be connected to an insulated copper equipment grounding conductor sized in accordance with Table 250.122.Exception No. 1: The requirements of 517.18(B) shall not apply to psychiatric, substance abuse, and rehabilitation hospitals meeting the requirements of 517.10(B)(2).Exception No. 2: Psychiatric security rooms shall not be required to have receptacle outlets installed in the room.Informational Note: It is not intended that there be a total, immediate replacement of existing non–hospital grade recepta‐ cles. It is intended, however, that non–hospital grade receptacles be replaced with hospital grade receptacles upon modification of use, renovation, or as existing receptacles need replacement.
3. Designated General Care (Category 2) Pediatric Locations. Receptacles that are located within the patient rooms, bath‐ rooms, playrooms, and activity rooms of pediatric units or spaces with similar risk as determined by the governing body, other than nurseries, shall be listed tamper-resistant or shall employ a listed tamper-resistant cover. [99:6.3.2.2.6.2(F)]
Critical Care (Category 1) Spaces.
1. Patient Bed Location Branch Circuits. Each patient bed location shall be supplied by at least two branch circuits, one or more from the critical branch and one or more circuits from the normal system. At least one branch circuit from the critical branch shall supply an outlet(s) only at that bed location.The electrical receptacles or the cover plates for the electri‐ cal receptacles supplied from the life safety and critical branches shall have a distinctive color or marking so as to be readily identifiable. [99:6.4.2.2.6.2(C)]All branch circuits from the normal system shall be from a single panelboard. Critical branch receptacles shall be identi‐ fied and shall also indicate the panelboard and circuit number supplying them.The branch circuit serving patient bed locations shall not be part of a multiwire branch circuit.Exception No. 1: Branch circuits serving only special-purpose recepta‐ cles or equipment in critical care (Category 1) spaces shall be permitted to be served by other panelboards.Exception No. 2: Critical care (Category 1) spaces served from two sepa‐ rate critical branch transfer switches shall not be required to have circuits from the normal system.
2. Patient Bed Location Receptacles.
  1. Minimum Number and Supply. Each patient bed location shall be provided with a minimum of 14 receptacles, at least one of which shall be connected to either of the following:
    1. The normal system branch circuit required in 517.19(A)
    2. A critical branch circuit supplied by a different transfer switch than the other receptacles at the same patient bed location
    (2) Receptacle Requirements. The receptacles required in 517.19(B)(1) shall be permitted to be single, duplex, or quad‐ ruplex type or any combination thereof. All receptacles shall be listed “hospital grade” and shall be so identified. The ground‐ ing terminal of each receptacle shall be connected to the refer‐ ence grounding point by means of an insulated copper equipment grounding conductor.
3. Operating Room Receptacles.
  1. Minimum Number and Supply. Each operating room shall be provided with a minimum of 36 receptacles divided between at least two branch circuits. At least 12 receptacles, but no more than 24, shall be connected to either of the following:
    1. The normal system branch circuit required in 517.19(A)
    2. A critical branch circuit supplied by a different transfer switch than the other receptacles at the same location
    (2) Receptacle Requirements. The receptacles shall be permitted to be of the locking or nonlocking type, single, duplex, or quadruplex types or any combination of the three.All nonlocking-type receptacles shall be listed hospital grade and so identified. The grounding terminal of each receptacle shall be connected to the reference grounding point by means of an insulated copper equipment grounding conductor.
4. Patient Care Vicinity Grounding and Bonding (Optional). A patient care vicinity shall be permitted to have a patient equipment grounding point. The patient equipment ground‐ ing point, where supplied, shall be permitted to contain one or more listed grounding and bonding jacks. An equipment bond‐ ing jumper not smaller than 10 AWG shall be used to connect the grounding terminal of all grounding-type receptacles to the patient equipment grounding point. The bonding conductor shall be permitted to be arranged centrically or looped as convenient.Informational Note: Where there is no patient equipment grounding point, it is important that the distance between the reference grounding point and the patient care vicinity be as short as possible to minimize any potential differences.
5. Equipment Grounding and Bonding. Where a grounded electrical distribution system is used and metal feeder raceway or Type MC or MI cable that qualifies as an equipment ground‐ ing conductor in accordance with 250.118 is installed, ground‐ ing of enclosures and equipment, such as panelboards, switchboards, and switchgear, shall be ensured by one of the following bonding means at each termination or junction point of the metal raceway or Type MC or MI cable:
  1. A grounding bushing and a continuous copper bonding jumper, sized in accordance with 250.122, with the bond‐ ing jumper connected to the junction enclosure or the ground bus of the panel
  2. Connection of feeder raceways or Type MC or MI cable to threaded hubs or bosses on terminating enclosures
  3. Other approved devices such as bonding-type locknuts or bushings. Standard locknuts shall not be used for bond‐ ing.
6. Additional Protective Techniques in Critical Care (Cate‐ gory 1) Spaces (Optional). Isolated power systems shall be permitted to be used for critical care (Category 1) spaces, and, if used, the isolated power system equipment shall be listed as isolated power equipment. The isolated power system shall be designed and installed in accordance with 517.160.Exception: The audible and visual indicators of the line isolation moni‐ tor shall be permitted to be located at the nursing station for the area being served.
7. Isolated Power System Equipment Grounding. Where an isolated ungrounded power source is used and limits the first- fault current to a low magnitude, the equipment grounding conductor associated with the secondary circuit shall be permit‐ ted to be run outside of the enclosure of the power conductors in the same circuit.Informational Note: Although it is permitted to run the ground‐ ing conductor outside of the conduit, it is safer to run it with the power conductors to provide better protection in case of a second ground fault.
8. Special-Purpose Receptacle Grounding. The equipment grounding conductor for special-purpose receptacles, such as the operation of mobile X-ray equipment, shall be extended to
the reference grounding points of branch circuits for all loca‐ tions likely to be served from such receptacles. Where such a circuit is served from an isolated ungrounded system, the grounding conductor shall not be required to be run with the power conductors; however, the equipment grounding termi‐ nal of the special-purpose receptacle shall be connected to the reference grounding point.
Wet Procedure Locations.
1. Receptacles and Fixed Equipment. Wet procedure loca‐ tions shall be provided with special protection against electric shock by one of the following means:
  1. Power distribution system that inherently limits the possi‐ ble ground-fault current due to a first fault to a low value, without interrupting the power supply
  2. Power distribution system in which the power supply is interrupted if the ground-fault current does, in fact, exceed a value of 6 mAException: Branch circuits supplying only listed, fixed, therapeutic and diagnostic equipment shall be permitted to be supplied from a grounded service, single- or 3-phase system, provided that
    1. Wiring for grounded and isolated circuits does not occupy the same raceway, and
    2. All conductive surfaces of the equipment are connected to an insulated copper equipment grounding conductor.
2. Isolated Power Systems. Where an isolated power system is utilized, the isolated power equipment shall be listed as isola‐ ted power equipment, and the isolated power system shall be designed and installed in accordance with 517.160.
Informational Note: For requirements for installation of thera‐ peutic pools and tubs, see Part VI of Article 680.
Ground-Fault Circuit-Interrupter Protection for Personnel. Ground-fault circuit-interrupter protection for personnel shall not be required for receptacles installed in those critical care (Category 1) spaces where the toilet and basin are installed within the patient room.

Part III. Essential Electrical System

Scope. The essential electrical system for these facili‐ ties shall comprise a system capable of supplying a limited amount of lighting and power service, which is considered essential for life safety and orderly cessation of procedures during the time normal electrical service is interrupted for any reason. This includes clinics, medical and dental offices, outpa‐ tient facilities, nursing homes, limited care facilities, hospitals, and other health care facilities serving patients.Informational Note: For information on the need for an essen‐ tial electrical system, see NFPA 99 -2015, Health Care Facilities Code.
Application of Other Articles. The life safety branch of the essential electrical system shall meet the requirements of Article 700, except as amended by Article 517.

Informational Note No. 1: For additional information, see NFPA 110-2013, Standard for Emergency and Standby Power Systems.

Informational Note No. 2: For additional information, see 517.29 and NFPA 99-2015, Health Care Facilities Code.

Essential Electrical Systems for Hospitals and Other Health Care Facilities.
1. Applicability. The requirements of Part III, 517.29 through 517.30, shall apply to critical care (Category 1) and general care (Category 2) hospitals and other health care facili‐ ties using Type 1 essential electrical systems where patients are sustained by electrical life-support equipment.Informational Note No. 1: For performance, maintenance, and testing requirements of essential electrical systems in hospitals, see NFPA 99 -2015, Health Care Facilities Code. For installation of centrifugal fire pumps, see NFPA 20-2013, Standard for the Instal‐ lation of Stationary Pumps for Fire Protection.Informational Note No. 2: For additional information on Type 1 and Type 2 essential electrical systems, see NFPA 99-2015, Health Care Facilities Code.N
2. Critical care (Category 1) spaces shall be served only by a Type 1 essential electrical system. [99:6.3.2.2.10.1]
Sources of Power.
1. Two Independent Power Sources. Essential electrical systems shall have a minimum of the following two independ‐ ent sources of power: a normal source generally supplying the entire electrical system and one or more alternate source(s) for use when the normal source is interrupted. [99:6.4.1.1.4]
2. Types of Power Sources.•
  1. Generating Units. Where the normal source consists ofgenerating units on the premises, the alternate source shall be either another generating set or an external utility service. [99:6.4.1.1.5]N
  2. Fuel Cell Systems. Fuel cell systems shall be permitted to serve as the alternate source for all or part of an essential elec‐ trical system, provided the following conditions apply:
    1. Installation of fuel cells shall comply with the require‐ ments in Parts I through VII of Article 692 for 1000 volts or less and Part VIII for over 1000 volts.Informational Note: For information on installation of station‐ ary fuel cells, see NFPA 853-2015, Standard for Installation of Stationary Fuel Cell Power Systems. [99:6.4.1.1.7]
    2. N + 1 units shall be provided where N units have suffi‐ cient capacity to supply the demand loads of the portion of the system served. [99:6.4.1.7.2]
    3. System shall be able to assume loads within 10 seconds of loss of normal power source.
    4. System shall have a continuing source of fuel supply, together with sufficient on-site fuel storage for the essen‐ tial system type.
    5. A connection shall be provided for a portable diesel generator to supply life safety and critical portions of the distribution system. [99:6.4.1.1.7.5(1) through (5)]
    6. Fuel cell systems shall be listed for emergency system use.
3. Location of Essential Electrical System Components. Essential electrical system components shall be located to mini‐ mize interruptions caused by natural forces common to the area (e.g., storms, floods, earthquakes, or hazards created by adjoining structures or activities). Installations of electrical services shall be located to reduce possible interruption of normal electrical services resulting from similar causes as well as possible disruption of normal electrical service due to inter‐ nal wiring and equipment failures. Feeders shall be located to
provide physical separation of the feeders of the alternate source and from the feeders of the normal electrical source to prevent possible simultaneous interruption.Informational Note: Facilities in which the normal source of power is supplied by two or more separate central station-fed services experience greater than normal electrical service relia‐ bility than those with only a single feed. Such a dual source of normal power consists of two or more electrical services fed from separate generator sets or a utility distribution network that has multiple power input sources and is arranged to provide mechanical and electrical separation so that a fault between the facility and the generating sources is not likely to cause an interruption of more than one of the facility service feeders.
Requirements for the Essential Electrical System.
1. Separate Branches. Essential electrical systems for hospi‐ tals shall be comprised of three separate branches capable of supplying a limited amount of lighting and power service that is considered essential for life safety and effective hospital oper‐ ation during the time the normal electrical service is interrup‐ ted for any reason. The three branches are life safety, critical, and equipment.The division between the branches shall occur at transfer switches where more than one transfer switch is required [99:6.4.2.2.1.2]
2. Transfer Switches. The number of transfer switches to be used shall be based on reliability and design. Each branch of the essential electrical system shall have one or more transfer switches.One transfer switch and downstream distribution system shall be permitted to serve one or more branches in a facility with a maximum demand on the essential electrical system of 150 kVA.Informational Note No. 1: See NFPA 99-2015, Health Care Facili‐ ties Code, 6.4.3.2, Transfer Switches; 6.4.2.1.5, Automatic Transfer Switch Features; 6.4.2.1.5.15, Nonautomatic Transfer Switch Features; and 6.4.2.1.7, Nonautomatic Transfer Device Features.Informational Note No. 2: See Informational Note Figure 517.31(a).Informational Note No. 3: See Informational Note Figure 517.31(b).(1) Optional Loads. Loads served by the generating equip‐ ment not specifically named in Article 517 shall be served by their own transfer switches such that the following conditions apply:
  1. These loads shall not be transferred if the transfer will overload the generating equipment.
  2. These loads shall be automatically shed upon generating equipment overloading.
  (2) Contiguous Facilities. Hospital power sources and alter‐ nate power sources shall be permitted to serve the essential electrical systems of contiguous or same site facilities.
3. Wiring Requirements.
  1. Separation from Other Circuits. The life safety branch and critical branch of the essential electrical system shall be kept entirely independent of all other wiring and equipment and shall not enter the same raceways, boxes, or cabinets with each other or other wiring.
    
    Normal source
    Nonessential loads
    Automatic switching equipment
    Equipment
    Alternate power source
    Life safety Critical
    1. Is in transfer equipment enclosures
    2. Is in exit or emergency luminaires supplied from two sources
    3. Is in a common junction box attached to exit or emer‐ gency luminaires supplied from two sources
    4. Is for two or more circuits supplied from the same branch and same transfer switchThe wiring of the equipment branch shall be permitted to occupy the same raceways, boxes, or cabinets of other circuits that are not part of the essential electrical system.
      1. Isolated Power Systems. Where isolated power systems are installed in any of the areas in 517.34(A)(1) and (A)(2), each
        Delayedbranchbranchbranchsystem shall be supplied by an individual circuit serving noother load.automatic switching equipmentEssential electrical system
      2. Mechanical Protection of the Essential Electrical System.
      The wiring of the life safety and critical branches shall beInformational Note Figure 517.31(a) Hospital — Minimum Requirement (greater than 150 kVA) for Transfer Switch Arrangement.mechanically protected. Where installed as branch circuits in patient care spaces, the installation shall comply with the requirements of 517.13(A) and (B). Only the following wiring methods shall be permitted:
      1. Nonflexible metal raceways, Type MI cable, Type RTRCNormal power source
        Nonessential loads
        Automatic switching equipment
        Equipment branch
        Critical branchAlternate power source
        Life safety branchmarked with the suffix –XW, or Schedule 80 PVC conduit. Nonmetallic raceways shall not be used for branch circuits that supply patient care areas.
      2. Where encased in not less than 50 mm (2 in.) of concrete, Schedule 40 PVC conduit, flexible nonmetallic or jacketed metallic raceways, or jacketed metallic cable assemblies listed for installation in concrete. Nonmetallic raceways shall not be used for branch circuits that supply patient care areas.
      3. Listed flexible metal raceways and listed metal sheathed cable assemblies in any of the following:
        Where used in listed prefabricated medical headwalls
        In listed office furnishings
        Where fished into existing walls or ceilings, not other‐ wise accessible and not subject to physical damage
        Where necessary for flexible connection to equip‐ ment
        Essential electrical system
        Informational Note Figure 517.31(b) Hospital — Minimum Requirement (150 kVA or less) for Transfer Switch Arrangement.
        Where general care locations are served from two separate
      Flexible power cords of appliances or other utilization equipment connected to the emergency system.
      1. For equipment that requires a flexible connectiondue to movement, vibration, or operation
      2. Luminaires installed in rigid ceiling structures where there is no access above the ceiling space after the luminaire is installed
      Cables for Class 2 or Class 3 systems permitted by Part VI of this Article, with or without raceways.transfer switches on the essential electrical system in accord‐ ance with 517.18(A), Exception No. 3, the general care circuits from the two separate systems shall be kept independent of each other.Where critical care locations are served from two separate transfer switches on the essential electrical system in accord‐ ance with 517.19(A), Exception No. 2, the critical care circuits from the two separate systems shall be kept independent of each other.Wiring of the life safety branch and the critical branch shall be permitted to occupy the same raceways, boxes, or cabinets of other circuits not part of the branch where such wiring complies with one of the following:Informational Note: See 517.13 for additional grounding requirements in patient care areas.
4. Capacity of Systems. The essential electrical system shall have the capacity and rating to meet the maximum actual demand likely to be produced by the connected load.Feeders shall be sized in accordance with 215.2 and Part III of Article 220. The generator set(s) shall have the capacity and rating to meet the demand produced by the load at any given time.Demand calculations for sizing of the generator set(s) shall be based on any of the following:
  1. Prudent demand factors and historical data
  2. Connected load
  3. Feeder calculation procedures described in Article 220
  4. Any combination of the above
  The sizing requirements in 700.4 and 701.4 shall not apply to hospital generator set(s).
5. Receptacle Identification. The cover plates for the electri‐ cal receptacles or the electrical receptacles themselves supplied from the essential electrical system shall have a distinctive color or marking so as to be readily identifiable. [99:6.4.2.2.6.2(C)]
6. Feeders from Alternate Power Source. A single feeder supplied by a local or remote alternate source shall be permit‐ ted to supply the essential electrical system to the point at which the life safety, critical, and equipment branches are sepa‐ rated. Installation of the transfer equipment shall be permitted at other than the location of the alternate power source.
7. Coordination. Overcurrent protective devices serving the essential electrical system shall be coordinated for the period of time that a fault’s duration extends beyond 0.1 second.
Exception No. 1: Between transformer primary and secondary overcur‐ rent protective devices, where only one overcurrent protective device or set of overcurrent protective devices exists on the transformer secondary.Exception No. 2: Between overcurrent protective devices of the same size (ampere rating) in series.Informational Note: The terms coordination and coordinated as used in this section do not cover the full range of overcurrent conditions.
Branches Requiring Automatic Connection.
1. Those functions of patient care depending on lighting or appliances that are connected to the essential electrical system shall be divided into the life safety branch and the critical branch, as described in 517.33 and 517.34 .
2. The life safety and critical branches shall be installed and connected to the alternate power source specified in 517.30(A) and (B) so that all functions specified herein for the life safety and critical branches are automatically restored to operation within 10 seconds after interruption of the normal source. [99:6.4.3.1]
Life Safety Branch. No functions other than those listed in 517.33(A) through (H) shall be connected to the life safety branch. The life safety branch of the essential electrical system shall supply power for the following lighting, recepta‐ cles, and equipment.
1. Illumination of Means of Egress. Illumination of means of egress, such as lighting required for corridors, passageways, stairways, and landings at exit doors, and all necessary ways of approach to exits. Switching arrangements to transfer patient corridor lighting in hospitals from general illumination circuits to night illumination circuits shall be permitted, provided only one of two circuits can be selected and both circuits cannot be extinguished at the same time.Informational Note: See NFPA 101 -2015, Life Safety Code, Sections 7.8 and 7.9.
2. Exit Signs. Exit signs and exit directional signs.Informational Note: See NFPA 101 -2012, Life Safety Code, Section 7.10.
3. Alarm and Alerting Systems. Alarm and alerting systems including the following:(1) Fire alarm systems(2) Alarm and alerting systems (other than fire alarmsystems) shall be connected to the life safety branch or critical branch. [99:6.4.2.2.3.3]•
  (3) Alarms for systems used for the piping of nonflammable medical gases
  - (4) Mechanical, control, and other accessories required foreffective life safety systems operation shall be permitted to be connected to the life safety branch.
4. Communications Systems. Hospital communications systems, where used for issuing instructions during emergency conditions. [99:6.4.2.2.3.2(3)]
5. Generator Set Locations. Generator set locations as follows:
  1. Task illumination
  2. Battery charger for emergency battery-powered lighting unit(s)
  3. Select receptacles at the generator set location and essen‐ tial electrical system transfer switch locations. [99: 6.4.2.2.3.2(4)]
6. Generator Set Accessories. Generator set accessories as required for generator performance. Loads dedicated to a specific generator, including the fuel transfer pump(s), ventila‐ tion fans, electrically operated louvers, controls, cooling system, and other generator accessories essential for generator operation, shall be connected to the life safety branch or to the output terminals of the generator with overcurrent protective devices. [99:6.4.2.2.3.4]
7. Elevators. Elevator cab lighting, control, communica‐ tions, and signal systems. [99:6.4.2.2.3.2(5)]
8. Automatic Doors. Electrically powered doors used for building egress. [99:6.4.2.2.2.3.2(6)]
Critical Branch.
1. Task Illumination and Selected Receptacles. The critical branch of the essential electrical system shall supply power for task illumination, fixed equipment, selected receptacles, and special power circuits serving the following areas and functions related to patient care:
  1. Critical care (Category 1) spaces that utilize anesthetizing gases, task illumination, selected receptacles, and fixed equipment
  2. The isolated power systems in special environments
  3. Patient care spaces, task illumination, and selected recep‐ tacles in the following:
    1. Infant nurseries
    2. Medication preparation areas
    3. Pharmacy dispensing areas
    4. Selected acute nursing areas
    5. Psychiatric bed areas (omit receptacles)
    6. Ward treatment rooms
    7. Nurses’ stations (unless adequately lighted by corridor luminaires)
  4. Additional specialized patient care task illumination and receptacles, where needed
  5. Nurse call systems
  6. Blood, bone, and tissue banks
  7. Telephone and data equipment rooms and closets
  8. Task illumination, selected receptacles, and selected power circuits for the following:
    1. General care (Category 2) beds (at least one duplex receptacle in each patient bedroom)
    2. Angiographic labs
    3. Cardiac catheterization labs
    4. Coronary care units
    5. Hemodialysis rooms or areas
    6. Emergency room treatment areas (selected)
    7. Human physiology labs
    8. Intensive care units
    9. Postoperative recovery rooms (selected)
  9. Additional task illumination, receptacles, and selected power circuits needed for effective facility operation, including single-phase fractional horsepower motors, shall be permitted to be connected to the critical branch. [99:6.4.2.2.4.2(9)]
  N
2. Switching. It shall be permitted to control task illumina‐ tion on the critical branch.
3. Subdivision of the Critical Branch. It shall be permitted to subdivide the critical branch into two or more branches.
Informational Note: It is important to analyze the consequences of supplying an area with only critical care branch power when failure occurs between the area and the transfer switch. Some proportion of normal and critical power or critical power from separate transfer switches may be appropriate.
Equipment Branch Connection to Alternate Power Source. The equipment branch shall be installed and connec‐ ted to the alternate power source such that the equipment described in 517.35(A) is automatically restored to operation at appropriate time-lag intervals following the energizing of the essential electrical system. Its arrangement shall also provide for the subsequent connection of equipment described in 517.35(B). [99:6.4.2.2.5.2]

Exception: For essential electrical systems under 150 kVA, deletion of the time-lag intervals feature for delayed automatic connection to the equipment system shall be permitted.

Equipment for Delayed Automatic Connection. The following equipment shall be permitted to be arranged for delayed automatic connection to the alternate power source:
1. Central suction systems serving medical and surgical func‐ tions, including controls. Such suction systems shall be permitted on the critical branch.
2. Sump pumps and other equipment required to operate for the safety of major apparatus, including associated control systems and alarms.
3. Compressed air systems serving medical and surgical functions, including controls. Such air systems shall be permitted on the critical branch.
4. Smoke control and stair pressurization systems, or both.
5. Kitchen hood supply or exhaust systems, or both, if required to operate during a fire in or under the hood.
6. Supply, return, and exhaust ventilating systems for airborne infectious/isolation rooms, protective environ‐ ment rooms, exhaust fans for laboratory fume hoods, nuclear medicine areas where radioactive material is used, ethylene oxide evacuation, and anesthesia evacua‐ tion. Where delayed automatic connection is not appro‐ priate, such ventilation systems shall be permitted to be placed on the critical branch. [99:6.4.2.2.5.3(A)(6) and (B)]
7. Supply, return, and exhaust ventilating systems for operat‐ ing and delivery rooms.
8. Supply, return, exhaust ventilating systems and/or air- conditioning systems serving telephone equipment rooms and closets and data equipment rooms and closets.
Exception: Sequential delayed automatic connection to the alternate power source to prevent overloading the generator shall be permitted where engineering studies indicate it is necessary.
Equipment for Delayed Automatic or Manual Connection. The following equipment shall be permitted to be arranged for either delayed automatic or manual connection to the alter‐ nate power source:
1. Heating equipment to provide heating for operating, delivery, labor, recovery, intensive care, coronary care, nurseries, infection/isolation rooms, emergency treat‐ ment spaces, and general patient rooms and pressure maintenance (jockey or make-up) pump(s) for water- based fire protection systemsException: Heating of general patient rooms and infection/isolation rooms during disruption of the normal source shall not be required under any of the following conditions:
  1. The outside design temperature is higher than −6.7°C (20°F).
  2. The outside design temperature is lower than −6.7°C (20°F), and where a selected room(s) is provided for the needs of all confined patients, only such room(s) need be heated.
  3. The facility is served by a dual source of normal power.Informational Note No. 1: The design temperature is based on the 97.5 percent design value as shown in Chapter 24 of the ASHRAE Handbook of Fundamentals (2013).Informational Note No. 2: For a description of a dual source of normal power, see 517.30(C) .
2. An elevator(s) selected to provide service to patient, surgical, obstetrical, and ground floors during interrup‐ tion of normal power. In instances where interruption of normal power would result in other elevators stopping between floors, throw-over facilities shall be provided to allow the temporary operation of any elevator for the release of patients or other persons who may be confined between floors.
3. Hyperbaric facilities.
4. Hypobaric facilities.
5. Automatically operated doors.
6. Minimal electrically heated autoclaving equipment shall be permitted to be arranged for either automatic or manual connection to the alternate source.
7. Controls for equipment listed in 517.35 .
8. Other selected equipment shall be permitted to be served by the equipment system. [99:6.4.2.2.5.4(9)]
AC Equipment for Nondelayed Automatic Connection. Generator accessories, including but not limited to, the trans‐ fer fuel pump, electrically operated louvers, and other genera‐ tor accessories essential for generator operation shall be arranged for automatic connection to the alternate power source. [99:6.5.2.2.3.2]

•

Type 2 Essential Electrical Systems for Nursing Homesand Limited Care Facilities.

Informational Note: Nursing homes and other limited carefacilities can be classified as critical care (Category 1) or general care (Category 2) patient care space depending on the design and type of care administered in the facility. For small, less complex facilities, only minimal alternate lighting and alarm service may be required. At nursing homes and other limited care facilities where patients are not sustained by electrical life- support equipment or inpatient hospital care the requirements of 517.40 through 517.41 apply. If the level of care is compara‐ ble to that provided in a hospital, see the essential electrical system requirements of 517.29 through 517.30.
1. Applicability. The requirements of Part III, 517.40(C) through 517.41, shall apply to nursing homes and limited care facilities.Exception: The requirements of Part III, 517.40(C) through 517.41, shall not apply to freestanding buildings used as nursing homes and limited care facilities, provided that the following apply:
  1. Admitting and discharge policies are maintained that preclude the provision of care for any patient or resident who may need to be sustained by electrical life-support equipment.
  2. No surgical treatment requiring general anesthesia is offered.
  3. An automatic battery-operated system(s) or equipment shall be effective for at least 11∕2 hours and is otherwise in accordance with 700.12 and that shall be capable of supplying lighting for exit lights, exit corridors, stairways, nursing stations, medical preparation areas, boiler rooms, and communications areas. This system shall also supply power to operate all alarm systems.
  Informational Note: See NFPA 101-2015, Life Safety Code.
2. Inpatient Hospital Care Facilities. For those nursing homes and limited care facilities that admit patients who need to be sustained by electrical life support equipment, the essen‐ tial electrical system from the source to the portion of the facility where such patients are treated shall comply with the requirements of Part III, 517.29 through 517.30.
3. Facilities Contiguous or Located on the Same Site with Hospitals. Nursing homes and limited care facilities that are contiguous or located on the same site with a hospital shall be permitted to have their essential electrical systems supplied by the hospital.
Informational Note No. 2: Where optional loads include contig‐uous or same-site facilities not covered in this Code, see the requirements of Article 700 of this Code; NFPA 101 -2015, Life Safety Code; and other applicable NFPA requirements for emer‐ gency egress under loadshed conditions.Informational Note No. 1: For performance, maintenance, and testing requirements of essential electrical systems in nursing homes and limited care facilities, see NFPA 99-2015, Health Care Facilities Code.
Required Power Sources.
1. Two Independent Power Sources. Essential electrical systems shall have a minimum of the following two independ‐ ent sources of power: a normal source generally supplying the entire electrical system and one or more alternate sources for use when the normal source is interrupted. [99:6.4.1.1.4]
2. Types of Power Sources. Where the normal source consists of generating units on the premises, the alternate source shall be either another generating set or an external utility service. [99:6.4.1.1.5]•
3. Location of Essential Electrical System Components.
Essential electrical systems shall be located to minimize inter‐ruptions caused by natural forces common to the area (e.g., storms, floods, earthquakes, or hazards created by adjoining structures or activities). Installations of electrical services shall be located to reduce possible interruption of normal electrical services resulting from similar causes as well as possible disrup‐ tion of normal electrical service due to internal wiring and equipment failures. Feeders shall be located to give physical separation of the feeders of the alternate source and from the feeders of the normal electrical source to prevent possible simultaneous interruption.
Essential Electrical Systems.

The division between the branches shall occur at transfer

switches where more than one transfer switch is required.

General. Essential electrical systems for nursing homes and limited care facilities shall be divided into the following two branches, the life safety branch and the equipment branch. [99:6.5.2.2.1.2]
Informational Note No. 2: For more information see NFPA99-2015, Health Care Facilities Code.Informational Note No. 1: Essential electrical systems are comprised of two separate branches capable of supplying a limi‐ ted amount of lighting and power service, which is considered essential for the protection of life and safety and effective opera‐ tion of the institution during the time normal electrical service is interrupted for any reason.
Transfer Switches. The number of transfer switches to be used shall be based on reliability, design, and load considera‐ tions. [99:6.5.2.2.1.4]
1. Each branch of the essential electrical system shall have one or more transfer switches. [99:6.5.2.2.1.4(A)]
2. One transfer switch shall be permitted to serve one or more branches or systems in a facility with a continuous load on the switch of 150 kVA (120 kW) or less. [99: 6.5.2.2.1.4(B)]
Informational Note No. 1: See NFPA 99-2015, Health Care Facili‐ ties Code, 6.5.3.2, Transfer Switch Operation Type II; 6.4.2.1.5, Automatic Transfer Switch Features; and 6.4.2.1.7, Nonauto‐ matic Transfer Device Features.Informational Note No. 2: See Informational Note Figure 517.42(a).Informational Note No. 3: See Informational Note Figure 517.42(b).
Capacity of System. The essential electrical system shall have adequate capacity to meet the demand for the operation of all functions and equipment to be served by each branch at one time.
Separation from Other Circuits. The life safety branch and equipment branch shall be kept entirely independent of all other wiring and equipment. [99:6.5.2.2.4.1]These circuits shall not enter the same raceways, boxes, or cabinets with other wiring except as follows:
1. In transfer switches
2. In exit or emergency luminaires supplied from two sour‐ ces
3. In a common junction box attached to exit or emergency luminaires supplied from two sourcesInformational Note: For further information see NFPA 99-2015Health Care Facilities Code, A.6.5.2.2.4.1.•
  
  Normal power source
  Nonessential loads
  Automatic switching equipment
  Delayed automatic switching
  Equipment branch
  Alternate power source
  Life safety branch
  1. Illumination of Means of Egress. Illumination of means of egress as is necessary for corridors, passageways, stairways, landings, and exit doors and all ways of approach to exits. Switching arrangement to transfer patient corridor lighting from general illumination circuits shall be permitted, providing only one of two circuits can be selected and both circuits cannot be extinguished at the same time.Informational Note: See NFPA 101 -2015, Life Safety Code, Sections 7.8 and 7.9.
  2. Exit Signs. Exit signs and exit directional signs.Informational Note: See NFPA 101 -2015, Life Safety Code, Section 7.10.
  3. Alarm and Alerting Systems. Alarm and alerting systems, including the following:equipment
    Essential electrical system
    1. Fire alarmsInformational Note: See NFPA 101 -2015, Life Safety Code,Informational Note Figure 517.42(a) Nursing Home and Limited Health Care Facilities — Minimum Requirement (greater than 150 kVA) for Transfer Switch Arrangement.Sections 9.6 and 18.3.4.
    2. Alarms required for systems used for the piping of nonflammable medical gases
    Normal power source
    Nonessential loads
    Automatic switching equipment
    Equipment branch
    Alternate power source
    Life safety branchInformational Note: See NFPA 99 -2015, Health Care Facilities Code, 6.5.2.2.2.1(3).
  4. Communications Systems. Communications systems, where used for issuing instructions during emergency condi‐ tions. [99:6.5.2.2.2.1(4)]
  5. Dining and Recreation Areas. Sufficient lighting in dining and recreation areas to provide illumination to exit ways at a minimum of 5 ft-candles. [99:6.5.2.2.2.1.(5)]
  6. Generator Set Location. Task illumination and selected receptacles in the generator set location. [99: 6.5.2.2.2.1(6)]
  7. Elevators. Elevator cab lighting, control, communica‐ tions, and signal systems. [99: 6.5.2.2.2.1(7)]

Connection to Equipment Branch. The equipment branch shall be installed and connected to the alternate power source so that the equipment listed in 517.44(A) shall be auto‐Essential electrical system
Informational Note Figure 517.42(b) Nursing Home and Limited Health Care Facilities — Minimum Requirement (150 kVA or less) for Transfer Switch Arrangement.
(E) Receptacle Identification. The electrical receptacles or the cover plates for the electrical receptacles supplied from the life safety or equipment branches shall have a distinctive color or marking to be readily identifiable. [99:6.5.2.2.4.2]•Informational Note: If color is used to identify these receptacles,the same color should be used throughout the facility. [99:A.6.5.2.2.4.2]517.43 Automatic Connection to Life Safety Branch. The life safety branch shall be installed and connected to the alternate source of power so that all functions specified herein shall be automatically restored to operation within 10 seconds after the interruption of the normal source. No functions other than those listed in 517.43(A) through (G) shall be connected to the life safety branch. The life safety branch shall supply power for the following lighting, receptacles, and equipment.matically restored to operation at appropriate time-lag intervals following the restoration of the life safety branch to operation. [99:6.5.2.2.3.1(A)]The equipment branch arrangement shall also provide for the additional connection of equipment listed in 517.44(B). [99:6.5.2.2.3.1]Exception: For essential electrical systems under 150 kVA, deletion of the time-lag intervals feature for delayed automatic connection to the equipment branch shall be permitted.
1. Delayed Automatic Connections to Equipment Branch. The following equipment shall be permitted to be connected to the equipment branch and shall be arranged for delayed automatic connection to the alternate power source:
  1. Task illumination and selected receptacles in the follow‐ ing:
    1. Patient care spaces
    2. Medication preparation spaces
    3. Pharmacy dispensing areas(2) Supply, return, and exhaust ventilating systems forairborne infectious isolation rooms
    4. Nurses’ stations (unless adequately lighted by corri‐ dor luminaires)
  1. Sump pumps and other equipment required to operate for the safety of major apparatus and associated control systems and alarms
  2. Smoke control and stair pressurization systems
  3. Kitchen hood supply or exhaust systems, or both, if required to operate during a fire in or under the hood
  4. Nurse call systems [99:6.5.2.2.3.3]
2. Delayed Automatic or Manual Connection to the Equip‐ ment Branch. The following equipment shall be permitted to be connected to the critical equipment branch and shall be arranged for either delayed automatic or manual connection to the alternate power source:
(1) Heating equipment to provide heating for patient rooms.Exception: Heating of general patient rooms during disruption of the normal source shall not be required under any of the following condi‐ tions:
1. The outside design temperature is higher than −6.7°C (20°F).
2. The outside design temperature is lower than −6.7°C (20°F) and where a selected room(s) is provided for the needs of all confined patients, only such room(s) need be heated.
3. The facility is served by a dual source of normal power as descri‐ bed in 517.41(C), Informational Note.Informational Note: The outside design temperature is based on the 97.5 percent design values, as shown in Chapter 24 of the ASHRAE Handbook of Fundamentals (2013).
4. Elevator service — in instances where disruption of power would result in elevators stopping between floors, throw-over facilities shall be provided to allow the temporary operation of any elevator for the release of passengers. For elevator cab lighting, control, and signal system requirements, see 517.43(G) .
5. Additional illumination, receptacles, and equipment shall be permitted to be connected only to the critical branch.
[99:6.5.2.2.3.4(A), (B), and (C)]•
Essential Electrical Systems for Other Health Care

Facilities.

Essential Electrical Distribution. If required by the governing body, the essential electrical distribution system for basic care (Category 3) patient care spaces shall be comprised of an alternate power system capable of supplying a limited amount of lighting and power service for the orderly cessation of procedures during a time normal electrical service is inter‐ rupted.Informational Note: See NFPA 99 -2015 , Health Care Facilities Code.
Electrical Life Support Equipment. Where electrical life support equipment is required, the essential electrical distribu‐ tion system shall be as described in 517.29 through 517.30.
Critical Care (Category 1) Patient Care Spaces. Where critical patient care (Category 1) spaces are present, the essen‐ tial electrical distribution system shall be as described in 517.29 through 517.30.N
General Care (Category 2) Patent Care Spaces. Where general care (Category 2) patent care spaces are present, the essential electrical distribution system shall be as described in517.40 through 517.45.
Power Systems. If required, alternate power sources acceptable to the governing body shall comply with the require‐ ments of NFPA 99-2015, Health Care Facilities Code.

Part IV. Inhalation Anesthetizing Locations

Informational Note: For further information regarding safe‐ guards for anesthetizing locations, see NFPA 99-2015, Health Care Facilities Code.

517.60 Anesthetizing Location Classification.

Informational Note: If either of the anesthetizing locations in 517.60(A) or 517.60(B) is designated a wet procedure location, refer to 517.20.

Hazardous (Classified) Location.
1. Use Location. In a location where flammable anesthetics are employed, the entire area shall be considered to be a Class I, Division 1 location that extends upward to a level1.52 m (5 ft) above the floor. The remaining volume up to the structural ceiling is considered to be above a hazardous (classi‐ fied) location. [99: Annex E, E.1, and E.2]
2. Storage Location. Any room or location in which flamma‐ ble anesthetics or volatile flammable disinfecting agents are stored shall be considered to be a Class I, Division 1 location from floor to ceiling.
Other-Than-Hazardous (Classified) Location. Any inhala‐ tion anesthetizing location designated for the exclusive use of nonflammable anesthetizing agents shall be considered to be an other-than-hazardous (classified) location.

Wiring and Equipment.
1. Within Hazardous (Classified) Anesthetizing Locations.
  1. Isolation. Except as permitted in 517.160, each power circuit within, or partially within, a flammable anesthetizing location as referred to in 517.60 shall be isolated from any distribution system by the use of an isolated power system.
  2. Design and Installation. Where an isolated power system is utilized, the isolated power equipment shall be listed as isolated power equipment, and the isolated power system shall be designed and installed in accordance with 517.160.
  3. Equipment Operating at More Than 10 Volts. In hazard‐ ous (classified) locations referred to in 517.60, all fixed wiring and equipment and all portable equipment, including lamps and other utilization equipment, operating at more than10 volts between conductors shall comply with the require‐ ments of 501.1 through 501.25, and 501.100 through 501.150, and 501.30(A) and 501.30(B) for Class I, Division 1 locations. All such equipment shall be specifically approved for the hazardous atmospheres involved.
  4. Extent of Location. Where a box, fitting, or enclosure is partially, but not entirely, within a hazardous (classified) loca‐ tion(s), the hazardous (classified) location(s) shall be consid‐ ered to be extended to include the entire box, fitting, or enclosure.
  5. Receptacles and Attachment Plugs. Receptacles and attachment plugs in a hazardous (classified) location(s) shall be listed for use in Class I, Group C hazardous (classified) loca‐ tions and shall have provision for the connection of a ground‐ ing conductor.
  6. Flexible Cord Type. Flexible cords used in hazardous (classified) locations for connection to portable utilization equipment, including lamps operating at more than 8 volts between conductors, shall be of a type approved for extra-hard usage in accordance with Table 400.4 and shall include an addi‐ tional conductor for grounding.
  7. Flexible Cord Storage. A storage device for the flexible cord shall be provided and shall not subject the cord to bend‐ ing at a radius of less than 75 mm (3 in.).
2. Above Hazardous (Classified) Anesthetizing Locations.
  1. Wiring Methods. Wiring above a hazardous (classified) location referred to in 517.60 shall be installed in rigid metal conduit, electrical metallic tubing, intermediate metal conduit, Type MI cable, or Type MC cable that employs a continuous, gas/vaportight metal sheath.
  2. Equipment Enclosure. Installed equipment that may produce arcs, sparks, or particles of hot metal, such as lamps and lampholders for fixed lighting, cutouts, switches, genera‐ tors, motors, or other equipment having make-and-break or sliding contacts, shall be of the totally enclosed type or be constructed so as to prevent escape of sparks or hot metal parti‐ cles.Exception: Wall-mounted receptacles installed above the hazardous (classified) location in flammable anesthetizing locations shall not be required to be totally enclosed or have openings guarded or screened to prevent dispersion of particles.
  3. Luminaires. Surgical and other luminaires shall conform to 501.130(B).Exception No. 1: The surface temperature limitations set forth in 501.130(B)(1) shall not apply.Exception No. 2: Integral or pendant switches that are located above and cannot be lowered into the hazardous (classified) location(s) shall not be required to be explosionproof.
  4. Seals. Listed seals shall be provided in conformance with 501.15, and 501.15(A)(4) shall apply to horizontal as well as to vertical boundaries of the defined hazardous (classified) loca‐ tions.
  5. Receptacles and Attachment Plugs. Receptacles and attachment plugs located above hazardous (classified) anesthe‐ tizing locations shall be listed for hospital use for services of prescribed voltage, frequency, rating, and number of conduc‐ tors with provision for the connection of the grounding conductor. This requirement shall apply to attachment plugs and receptacles of the 2-pole, 3-wire grounding type for single- phase, 120-volt, nominal, ac service.
  6. 250-Volt Receptacles and Attachment Plugs Rated 50 and60 Amperes. Receptacles and attachment plugs rated 250 volts, for connection of 50-ampere and 60-ampere ac medi‐ cal equipment for use above hazardous (classified) locations, shall be arranged so that the 60-ampere receptacle will accept either the 50-ampere or the 60-ampere plug. Fifty-ampere receptacles shall be designed so as not to accept the 60-ampere attachment plug. The attachment plugs shall be of the 2-pole, 3-wire design with a third contact connecting to the insulated (green or green with yellow stripe) equipment grounding conductor of the electrical system.
3. Other-Than-Hazardous (Classified) Anesthetizing Loca‐ tions.
  1. Wiring Methods. Wiring serving other-than-hazardous (classified) locations, as defined in 517.60, shall be installed in a metal raceway system or cable assembly. The metal raceway system or cable armor or sheath assembly shall qualify as an equipment grounding conductor in accordance with 250.118. Type MC and Type MI cable shall have an outer metal armor, sheath, or sheath assembly that is identified as an acceptable equipment grounding conductor.Exception: Pendant receptacle installations that employ listed Type SJO or equivalent hard usage or extra-hard usage, flexible cords suspended not less than 1.8 m (6 ft) from the floor shall not be required to be installed in a metal raceway or cable assembly.
  2. Receptacles and Attachment Plugs. Receptacles and attachment plugs installed and used in other-than-hazardous (classified) locations shall be listed “hospital grade” for services of prescribed voltage, frequency, rating, and number of conductors with provision for connection of the grounding conductor. This requirement shall apply to 2-pole, 3-wire grounding type for single-phase, 120-, 208-, or 240-volt, nomi‐ nal, ac service.
  3. 250-Volt Receptacles and Attachment Plugs Rated
50 Amperes and 60 Amperes. Receptacles and attachment plugs rated 250 volts, for connection of 50-ampere and 60-ampere ac medical equipment for use in other-than- hazardous (classified) locations, shall be arranged so that the 60-ampere receptacle will accept either the 50-ampere or the 60-ampere plug. Fifty-ampere receptacles shall be designed so as not to accept the 60-ampere attachment plug. The attach‐ ment plugs shall be of the 2-pole, 3-wire design with a third contact connecting to the insulated (green or green with yellow stripe) equipment grounding conductor of the electrical system.
Grounding. In any anesthetizing area, all metal race‐ ways and metal-sheathed cables and all normally non–current- carrying conductive portions of fixed electrical equipment shall be connected to an equipment grounding conductor. Ground‐ ing and bonding in Class I locations shall comply with 501.30.Exception: Equipment operating at not more than 10 volts between conductors shall not be required to be connected to an equipment grounding conductor.
Grounded Power Systems in Anesthetizing Locations.
1. Battery-Powered Lighting Units. One or more battery- powered lighting units shall be provided and shall be permitted to be wired to the critical lighting circuit in the area and connected ahead of any local switches.
2. Branch-Circuit Wiring. Branch circuits supplying only listed, fixed, therapeutic and diagnostic equipment, perma‐ nently installed above the hazardous (classified) location and in other-than-hazardous (classified) locations, shall be permit‐ ted to be supplied from a normal grounded service, single- or three-phase system, provided the following apply:
  1. Wiring for grounded and isolated circuits does not occupy the same raceway or cable.
  2. All conductive surfaces of the equipment are connected to an equipment grounding conductor.
  3. Equipment (except enclosed X-ray tubes and the leads to the tubes) is located at least 2.5 m (8 ft) above the floor or outside the anesthetizing location.
  4. Switches for the grounded branch circuit are located outside the hazardous (classified) location.
  Exception: Sections 517.63(B)(3) and (B)(4) shall not apply in other- than-hazardous (classified) locations.
3. Fixed Lighting Branch Circuits. Branch circuits supplying only fixed lighting shall be permitted to be supplied by a normal grounded service, provided the following apply:
  1. Such luminaires are located at least 2.5 m (8 ft) above the floor.
  2. All conductive surfaces of luminaires are connected to an equipment grounding conductor.
  3. Wiring for circuits supplying power to luminaires does not occupy the same raceway or cable for circuits supply‐ ing isolated power.
  4. Switches are wall-mounted and located above hazardous (classified) locations.
  Exception: Sections 517.63(C)(1) and (C)(4) shall not apply in other- than-hazardous (classified) locations.
4. Remote-Control Stations. Wall-mounted remote-control stations for remote-control switches operating at 24 volts or less shall be permitted to be installed in any anesthetizing location.
5. Location of Isolated Power Systems. Where an isolated power system is utilized, the isolated power equipment shall be listed as isolated power equipment. Isolated power system equipment and its supply circuit shall be permitted to be loca‐ ted in an anesthetizing location, provided it is installed above a hazardous (classified) location or in an other-than-hazardous (classified) location.
6. Circuits in Anesthetizing Locations. Except as permitted above, each power circuit within, or partially within, a flamma‐ ble anesthetizing location as referred to in 517.60 shall be isola‐ ted from any distribution system supplying other-than- anesthetizing locations.
Low-Voltage Equipment and Instruments.

Equipment Requirements. Low-voltage equipment that is frequently in contact with the bodies of persons or has exposed current-carrying elements shall comply with one of the follow‐ ing:
1. Operate on an electrical potential of 10 volts or less
2. Be approved as intrinsically safe or double-insulated equipment
3. Be moisture resistant
Power Supplies. Power shall be supplied to low-voltage equipment from one of the following:
1. An individual portable isolating transformer (autotrans‐ formers shall not be used) connected to an isolated power circuit receptacle by means of an appropriate cord and attachment plug
2. A common low-voltage isolating transformer installed in an other-than-hazardous (classified) location
3. Individual dry-cell batteries
4. Common batteries made up of storage cells located in an other-than-hazardous (classified) location
Isolated Circuits. Isolating-type transformers for supply‐ ing low-voltage circuits shall have both of the following:
1. Approved means for insulating the secondary circuit from the primary circuit
2. The core and case connected to an equipment grounding conductor
Controls. Resistance or impedance devices shall be permitted to control low-voltage equipment but shall not be used to limit the maximum available voltage to the equipment.
Battery-Powered Appliances. Battery-powered appliances shall not be capable of being charged while in operation unless their charging circuitry incorporates an integral isolating-type transformer.
Receptacles or Attachment Plugs. Any receptacle or attachment plug used on low-voltage circuits shall be of a type that does not permit interchangeable connection with circuits of higher voltage.

Informational Note: Any interruption of the circuit, even circuits as low as 10 volts, either by any switch or loose or defec‐ tive connections anywhere in the circuit, may produce a spark that is sufficient to ignite flammable anesthetic agents.

Part V. X-Ray Installations

Applicability. Nothing in this part shall be construed as specifying safeguards against the useful beam or stray X-ray radiation.Informational Note No. 1: Radiation safety and performance requirements of several classes of X-ray equipment are regulated under Public Law 90-602 and are enforced by the Department of Health and Human Services.Informational Note No. 2: In addition, information on radiation protection by the National Council on Radiation Protection and Measurements is published as Reports of the National Council on Radiation Protection and Measurement. These reports are obtaina‐ ble from NCRP Publications, P.O. Box 30175, Washington, DC 20014.
Connection to Supply Circuit.
1. Fixed and Stationary Equipment. Fixed and stationary X-ray equipment shall be connected to the power supply by means of a wiring method complying with applicable require‐ ments of Chapters 1 through 4 of this Code, as modified by this article.Exception: Equipment properly supplied by a branch circuit rated at not over 30 amperes shall be permitted to be supplied through a suitable attachment plug and hard-service cable or cord.
2. Portable, Mobile, and Transportable Equipment. Individ‐ ual branch circuits shall not be required for portable, mobile, and transportable medical X-ray equipment requiring a capacity of not over 60 amperes.
3. Over 1000-Volt Supply. Circuits and equipment operated on a supply circuit of over 1000 volts shall comply with Arti‐ cle 490.
Disconnecting Means.
1. Capacity. A disconnecting means of adequate capacity for at least 50 percent of the input required for the momentary rating or 100 percent of the input required for the long-time
  rating of the X-ray equipment, whichever is greater, shall be provided in the supply circuit.
2. Location. The disconnecting means shall be operable from a location readily accessible from the X-ray control.
3. Portable Equipment. For equipment connected to a 120-volt branch circuit of 30 amperes or less, a grounding-type attachment plug and receptacle of proper rating shall be permitted to serve as a disconnecting means.
Rating of Supply Conductors and Overcurrent Protec‐ tion.
1. Diagnostic Equipment.
  1. Branch Circuits. The ampacity of supply branch-circuit conductors and the current rating of overcurrent protective devices shall not be less than 50 percent of the momentary rating or 100 percent of the long-time rating, whichever is greater.
  2. Feeders. The ampacity of supply feeders and the current rating of overcurrent protective devices supplying two or more branch circuits supplying X-ray units shall not be less than 50 percent of the momentary demand rating of the largest unit plus 25 percent of the momentary demand rating of the next largest unit plus 10 percent of the momentary demand rating of each additional unit. Where simultaneous biplane examina‐ tions are undertaken with the X-ray units, the supply conduc‐ tors and overcurrent protective devices shall be 100 percent of the momentary demand rating of each X-ray unit.Informational Note: The minimum conductor size for branch and feeder circuits is also governed by voltage regulation requirements. For a specific installation, the manufacturer usually specifies minimum distribution transformer and conduc‐ tor sizes, rating of disconnecting means, and overcurrent protec‐ tion.
2. Therapeutic Equipment. The ampacity of conductors and rating of overcurrent protective devices shall not be less than
100 percent of the current rating of medical X-ray therapy equipment.Informational Note: The ampacity of the branch-circuit conduc‐ tors and the ratings of disconnecting means and overcurrent protection for X-ray equipment are usually designated by the manufacturer for the specific installation.
Control Circuit Conductors.
1. Number of Conductors in Raceway. The number of control circuit conductors installed in a raceway shall be deter‐ mined in accordance with 300.17.
2. Minimum Size of Conductors. Size 18 AWG or 16 AWG fixture wires as specified in 725.49 and flexible cords shall be permitted for the control and operating circuits of X-ray and auxiliary equipment where protected by not larger than 20-ampere overcurrent devices.
Equipment Installations. All equipment for new X-ray installations and all used or reconditioned X-ray equipment moved to and reinstalled at a new location shall be of an approved type.
Transformers and Capacitors. Transformers and capacitors that are part of X-ray equipment shall not be required to comply with Articles 450 and 460.Capacitors shall be mounted within enclosures of insulating material or grounded metal.
Installation of High-Tension X-Ray Cables. Cables with grounded shields connecting X-ray tubes and image intensifi‐ ers shall be permitted to be installed in cable trays or cable troughs along with X-ray equipment control and power supply conductors without the need for barriers to separate the wiring.
Guarding and Grounding.

High-Voltage Parts. All high-voltage parts, including X-ray tubes, shall be mounted within grounded enclosures. Air, oil, gas, or other suitable insulating media shall be used to insulate the high-voltage from the grounded enclosure. The connection from the high-voltage equipment to X-ray tubes and other high-voltage components shall be made with high-voltage shiel‐ ded cables.
Low-Voltage Cables. Low-voltage cables connecting to oil- filled units that are not completely sealed, such as transform‐ ers, condensers, oil coolers, and high-voltage switches, shall have insulation of the oil-resistant type.
Non–Current-Carrying Metal Parts. Non–current- carrying metal parts of X-ray and associated equipment (controls, tables, X-ray tube supports, transformer tanks, shiel‐ ded cables, X-ray tube heads, etc.) shall be connected to an equipment grounding conductor in the manner specified in Part VII of Article 250, as modified by 517.13(A) and (B).

Part VI. Communications, Signaling Systems, Data Systems, Fire Alarm Systems, and Systems Less Than 120 Volts, Nominal

Patient Care Spaces. Equivalent insulation and isola‐ tion to that required for the electrical distribution systems in patient care areas shall be provided for communications, signaling systems, data system circuits, fire alarm systems, and systems less than 120 volts, nominal.Class 2 and Class 3 signaling and communications systems and power-limited fire alarm systems shall not be required to comply with the grounding requirements of 517.13, to comply with the mechanical protection requirements of 517.31(C)(3)(5), or to be enclosed in raceways, unless other‐ wise specified by Chapter 7 or 8.Secondary circuits of transformer-powered communications or signaling systems shall not be required to be enclosed in raceways unless otherwise specified by Chapter 7 or 8. [99:6.4.2.2.6.6]
Other-Than-Patient-Care Areas. In other-than-patient- care areas, installations shall be in accordance with the applica‐ ble provisions of other parts of this Code.
Signal Transmission Between Appliances.

General. Permanently installed signal cabling from an appliance in a patient location to remote appliances shall employ a signal transmission system that prevents hazardous grounding interconnection of the appliances.Informational Note: See 517.13(A) for additional grounding requirements in patient care areas.
Common Signal Grounding Wire. Common signal grounding wires (i.e., the chassis ground for single-ended transmission) shall be permitted to be used between appliances all located within the patient care vicinity, provided the appli‐ ances are served from the same reference grounding point.

Part VII. Isolated Power Systems

517.160 Isolated Power Systems.

Installations.
1. Isolated Power Circuits. Each isolated power circuit shall be controlled by a switch or circuit breaker that has a discon‐ necting pole in each isolated circuit conductor to simultane‐ ously disconnect all power. Such isolation shall be accomplished by means of one or more isolation transformers, by means of generator sets, or by means of electrically isolated batteries. Conductors of isolated power circuits shall not be installed in cables, raceways, or other enclosures containing conductors of another system.
2. Circuit Characteristics. Circuits supplying primaries of isolating transformers shall operate at not more than 600 volts between conductors and shall be provided with proper overcur‐ rent protection. The secondary voltage of such transformers shall not exceed 600 volts between conductors of each circuit. All circuits supplied from such secondaries shall be ungroun‐ ded and shall have an approved overcurrent device of proper ratings in each conductor. Circuits supplied directly from batteries or from motor generator sets shall be ungrounded and shall be protected against overcurrent in the same manner as transformer-fed secondary circuits. If an electrostatic shield is present, it shall be connected to the reference grounding point. [99:6.3.2.6.1]
3. Equipment Location. The isolating transformers, motor generator sets, batteries and battery chargers, and associated primary or secondary overcurrent devices shall not be installed in hazardous (classified) locations. The isolated secondary circuit wiring extending into a hazardous anesthetizing loca‐ tion shall be installed in accordance with 501.10.
4. Isolation Transformers. An isolation transformer shall not serve more than one operating room except as covered in (A)(4)(a) and (A)(4)(b).For purposes of this section, anesthetic induction rooms are considered part of the operating room or rooms served by the induction rooms.
  1. Induction Rooms. Where an induction room serves more than one operating room, the isolated circuits of the induction room shall be permitted to be supplied from the isolation transformer of any one of the operating rooms served by that induction room.
  2. Higher Voltages. Isolation transformers shall be permitted to serve single receptacles in several patient areas where the following apply:
    1. The receptacles are reserved for supplying power to equipment requiring 150 volts or higher, such as portable X-ray units.
    2. The receptacles and mating plugs are not interchangea‐ ble with the receptacles on the local isolated power system.
    [99:13.4.1.2.6.6]
5. Conductor Identification. The isolated circuit conductors shall be identified as follows:
  1. Isolated Conductor No. 1 — Orange with at least one distinctive colored stripe other than white, green, or gray along the entire length of the conductor
  2. Isolated Conductor No. 2 — Brown with at least one distinctive colored stripe other than white, green, or gray along the entire length of the conductor
  For 3-phase systems, the third conductor shall be identified as yellow with at least one distinctive colored stripe other than white, green, or gray along the entire length of the conductor. Where isolated circuit conductors supply 125-volt, single-phase, 15- and 20-ampere receptacles, the striped orange conduc‐ tor(s) shall be connected to the terminal(s) on the receptacles that are identified in accordance with 200.10(B) for connec‐ tion to the grounded circuit conductor.(6) Wire-Pulling Compounds. Wire-pulling compounds that increase the dielectric constant shall not be used on the secon‐ dary conductors of the isolated power supply.Informational Note No. 1: It is desirable to limit the size of the isolation transformer to 10 kVA or less and to use conductor insulation with low leakage to meet impedance requirements.Informational Note No. 2: Minimizing the length of branch- circuit conductors and using conductor insulations with a dielec‐ tric constant less than 3.5 and insulation resistance constant greater than 6100 megohm-meters (20,000 megohm-feet) at 16°C (60°F) reduces leakage from line to ground, reducing the hazard current.
Line Isolation Monitor.
1. Characteristics. In addition to the usual control and over‐ current protective devices, each isolated power system shall be provided with a listed continually operating line isolation moni‐ tor that indicates total hazard current. The monitor shall be designed such that a green signal lamp, conspicuously visible to persons in each area served by the isolated power system, remains lighted when the system is adequately isolated from ground. An adjacent red signal lamp and an audible warning signal (remote if desired) shall be energized when the total hazard current (consisting of possible resistive and capacitive leakage currents) from either isolated conductor to ground reaches a threshold value of 5 mA under nominal line voltage conditions. The line monitor shall not alarm for a fault hazard of less than 3.7 mA or for a total hazard current of less than 5 mA.Exception: A system shall be permitted to be designed to operate at a lower threshold value of total hazard current. A line isolation monitor for such a system shall be permitted to be approved, with the provision that the fault hazard current shall be permitted to be reduced but not to less than 35 percent of the corresponding threshold value of the total hazard current, and the monitor hazard current is to be correspondingly reduced to not more than 50 percent of the alarm threshold value of the total hazard current.
2. Impedance. The line isolation monitor shall be designed to have sufficient internal impedance such that, when properly connected to the isolated system, the maximum internal current that can flow through the line isolation monitor, when any point of the isolated system is grounded, shall be 1 mA.Exception: The line isolation monitor shall be permitted to be of the low- impedance type such that the current through the line isolation monitor,ARTICLE 518 — ASSEMBLY OCCUPANCIES 518.4
  when any point of the isolated system is grounded, will not exceed twice the alarm threshold value for a period not exceeding 5 milliseconds.Informational Note: Reduction of the monitor hazard current, provided this reduction results in an increased “not alarm” threshold value for the fault hazard current, will increase circuit capacity.
3. Ammeter. An ammeter calibrated in the total hazard current of the system (contribution of the fault hazard current plus monitor hazard current) shall be mounted in a plainly visi‐ ble place on the line isolation monitor with the “alarm on” zone at approximately the center of the scale.

Exception: The line isolation monitor shall be permitted to be a compo‐ site unit, with a sensing section cabled to a separate display panel section on which the alarm or test functions are located.

Informational Note: It is desirable to locate the ammeter so that it is conspicuously visible to persons in the anesthetizing loca‐ tion.

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