grounding fire pump
The NEC (230.82(5)) does permit the fire pump to be connected to the load side of the service disconnect if provided with service equipment (meaning service disconnect and grounded per 250) and installed in accordance with requirements for service-entrance conductors.
The UL standard (UL-218) does require protection for motor branch circuit and motor overcurrent protection as follows:
19 Circuit Breakers
19.1 The motor branch circuit shall be protected by a circuit breaker that complies with the Standard for
Molded-Case Circuit Breakers, Molded-Case Switches and Circuit-Breaker Enclosures, UL 489, connected directly to the load side of the isolating switch, when provided, with one pole connected to each ungrounded circuit conductor.
Exception: If the motor branch circuit is transferred to an alternate on-site power generator and is protected by an overcurrent device at the generator, the circuit breaker within the fire pump controller is
not required to be connected.
19.1 revised July 18, 2005
19.2 A circuit breaker shall have the following mechanical characteristics:
a) Be externally operable;
b) Be trip free of the handle; and
c) Be provided with a nameplate with the legend CIRCUIT BREAKER ? DISCONNECTING
MEANS in letters not less than 3/8 inches (10 mm) high, located on the outside of the
controller enclosure adjacent to the means for operating the circuit breaker.
19.3 A circuit breaker shall have the following electrical characteristics:
a) A continuous current rating not less than 115 percent of the rated full load current of the motor;
b) Overcurrent sensing elements of the nonthermal type;
c) Instantaneous short circuit overcurrent protection;
d) A short-circuit current interrupting rating at least equal to the short-circuit rating of the
controller;
Exception: A circuit breaker that is series rated in combination with an inherently-protected isolating switch is not required to have the short-circuit current interrupting rating;
e) Normal and emergency run mechanical starting of the motor without tripping; and
f) An instantaneous trip setting of not more than 20 times the full load current.
20 Motor Overcurrent Protection
20.1 An overcurrent protective device shall be provided on the load side of the isolating switch, if provided, and on the line side of the fire pump motor, located within the fire pump controller, and have the following characteristics:
a) For a squirrel-cage motor, the device shall be:
1) Of the time delay type having a tripping time between 8 and 20 seconds at locked rotor current. (This is 600 percent of rated full load current for a squirrel-cage motor); and
2) Calibrated to and set at a minimum of 300 percent of motor full load current.
b) Visual means or markings on the device shall be provided that clearly indicate that proper settings have been made;
c) The device shall be manually resettable for operation immediately after tripping, with the tripping characteristics unchanged; and
d) Tripping shall be accomplished by opening the circuit breaker (see 19.1 ), which shall be of the external manual reset type.
