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

-6J°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 described in 517.44(C), FPN.

FPN: The outside design temperature is based on the
97!/2 percent design values as shown in Chapter
24 of the ASHRAE Handbook of Fundamentals
(1997).

(2) 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 517.42(G).

(3) Additional illumination, receptacles, and equipment shall be permitted to be connected only to the critical branch.

[99:4.5.2.2.3.4(A), (B), and (C)]

517.44 Sources of Power.

(A) Two Independent Sources of Power. Essential electrical systems shall have a minimum of two independent 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. [99:4.4.1.1.4]

(B) Alternate Source of Power. The alternate source of power shall be a generator(s) driven by some form of prime mover(s) and located on the premises.

Exception No. 1: Where the normal source consists of generating units on the premises, the alternate source shall be either another generator set or an external utility service.

Exception No. 2: Nursing homes or limited care facilities meeting the requirement of 5J 7.40(A) and other health care facilities meeting the requirement of 517.45 shall be permitted to use a battery system or self-contained battery integral with the equipment.

(C) Location of Essential Electrical System Compo nents. Careful consideration shall be given to the location of the spaces housing the components of the essential electrical system to minimize interruptions caused by natural forces common to the area (e.g., storms, floods, earthquakes, or hazards created by adjoining structures or activities). Consideration shall also be given to the possible interruption of normal electrical services resulting from similar causes as well as possible disruption of normal electrical service due to internal wiring and equipment failures.

FPN: 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 reliability 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 will not likely cause an interruption of more than one of the facility service feeders.

517.45 Essential Electrical Systems for Other Health

Care Facilities.

(A) Essential Electrical Distribution. The essential electrical distribution system shall be a battery or