The disconnect placement as required by the NEC
VARYING REQUIREMENTS EXIST for the fire pump disconnect location, depending on the safety objective. Are we trying to locate the disconnect where it will not be affected by an occurrence within the building—including a fire or an electrical failure—or do we want to locate it so that it will not be disconnected by mistake because it is near other building disconnects? The answer is both.
A separate service or a tap ahead of the service are both acceptable sources of supply for a fire pump, so the disconnect for the fire pump is also frequently a service disconnect.
These sources are permitted by 230.2(A)(1), 230.82(5), 230.94 Exception No. 4 and 695.3(A)(1). Speaking to an additional service disconnecting means for fire pumps, 230.72(B) said the disconnect “shall be installed remote from the one to six service disconnecting means for normal service to minimize the possibility of simultaneous interruption of supply.”
This means that if the normal building service equipment should suffer a catastrophic occurrence, the fire pump disconnect should be so located that it will not be affected.
In 695.4(B)(2)(3), it is required that the fire pump disconnect “not be located within equipment that feeds loads other than the fire pump,” while 695.4(B)(2)(4) requires that the fire pump disconnect “be located sufficiently remote from other building or other fire pump source disconnecting means such that inadvertent contemporaneous operation would be unlikely.”
This decreases the likelihood that someone would mistake the fire pump disconnect for something else and turn it off. This is aided by the requirement in 695.4(B)(3) that the disconnect be marked “fire pump disconnecting means” in letters at least 1 inch in height and that the marking not be located behind doors or covers. Also, 695.4(B)(2)(2) requires the fire pump disconnect to be lockable in the closed position. Inadvertent operation would not be possible if the disconnect were locked in the closed position.
Another requirement is in 695.3(A)(1) that permits a fire pump to be supplied by a separate service or from a connection located ahead of “and not within the same cabinet, enclosure, or vertical switchboard section as the service disconnecting means. The connection shall be located and arranged so as to minimize the possibility of damage by fire from within the premises and from exposing hazards.”
The restriction against the fire pump disconnect being installed within the same vertical switchboard section as the service disconnect is a bit strange because even located in an adjacent section, the desired separation would probably not be obtained. This requirement is more lenient than those in 220.72(B) and 695.4(B)(2)(4) and (4).
It should be noted that only the installation of power sources and controls for fire pumps are found in Article 695. Rules for performance, maintenance and testing are found in NFPA 20-2003, Standard for the Installation of Stationary Pumps for Fire Protection.
Many of the sections in Article 695 are followed by references in brackets [ ] to NFPA 20, and these sections are extracted from NFPA 20.
Some changes in Article 695 in the 2005 National Electrical Code (NEC):
- 695.6(E) and 695.14(E): Added to the list of permitted control and pump wiring methods, Type MC cable with an impervious covering.
- 695.6(H): Ground-fault protection is not permitted for fire pumps. Obviously, all of the Article 695 rules are aimed at keeping the fire pump running as long as possible, even to destruction.
- 695.6(D): Feeders and branch circuits to be protected against short circuit only, not against overload.
- 695.5(B), (C)(2) and 695.4(B)(1): Clarification that the requirement to carry locked rotor current indefinitely applies to the overcurrent devices only, but not to conductors nor to other devices.
With all these differing requirements, it’s important to study the Code, to ensure that you have located your fire pump disconnect properly. EC
SCHWAN is an electrical Code consultant in Hayward, Calif. He can be reached at firstname.lastname@example.org.