Fire Fighting Pump set, Equipment Grounding Conductor

[AmmarAbdou]

Hi,
We have one Fire Fighting pump set (electrical 150 HP, jockey7.5 HP and diesel).380V 3phase system

*as per 695.6(B)(1) I have sized the conductors to 400 kcmil according to the FLA in the table 430.250.
*and as per 695.4(B)(2)(a)(1) I sized the Circuit breaker to be 1600A to carry indefinitely the LRC of the motors. from table 430.251(B).
*and the source of the 1600A breaker is tapped ahead of the service disconnect switch of the switchgear (i.e. the tap is between the transformer and the switch gear disconnect switch).
*Voltage drop is ok.

but I have some concerns:

1- As per 695.6(C) which states that "branch-circuit and feeder conductors shall be protected against short circuit only "
so, my cable will be 4Cx400 kcmil fire rated(I mean only 4 copper cores cable, 400 kcmil each, without a green-yellow earthing or grounding conductor) so, the circuit will be protected from the short circuit only.
if I run the grounding conductor, then it will be violation of the

695.6(C), because the circuit will be protected against short circuit and ground fault! am I right?!
please note that as per 695.6.(G) Ground fault protection of equipment is not permitted.

2-Can I use reduced neutral conductors for the fire fighting pumps power circuits?

Regards,
Ammar M. I.​

 

[ActionDave]

......

1- As per 695.6(C) which states that "branch-circuit and feeder conductors shall be protected against short circuit only "
so, my cable will be 4Cx400 kcmil fire rated(I mean only 4 copper cores cable, 400 kcmil each, without a green-yellow earthing or grounding conductor) so, the circuit will be protected from the short circuit only.
if I run the grounding conductor, then it will be violation of the

695.6(C), because the circuit will be protected against short circuit and ground fault! am I right?!please note that as per 695.6.(G) Ground fault protection of equipment is not permitted.​

I think the wording short circuit only is meant to make it clear that no overload protection is to be used, but it does bring up an interesting problem. Since all of the required wiring methods are metallic it would be impossible not to provide a Equipment Grounding Conductor. 695.(6)(G) is meant to make it clear that no electronic GFPE is to be used. There is some bad wording here, but I think the intent is that short circuit/ground fault protection in the form of an EGC should be run with the circuit conductors.

2-Can I use reduced neutral conductors for the fire fighting pumps power circuits?

Regards,
Ammar M. I.

You wouldn't use a neutral to power the fire pumps. Do you mean the control circuits for the pumps?

 

[Devin Hanes]

conductor, then it will be violation of the

695.6(C), because the circuit will be protected against short circuit and ground fault! am I right?!
please note that as per 695.6.(G) Ground fault protection of equipment is not permitted.

​

ARTICLE 100
Definitions
Ground-Fault Protection of Equipment.

A system intended to provide protection of equipment from damaging line-to ground fault currents by operating to cause a disconnecting means to open all ungrounded conductors of the faulted circuit. This protection is provided at current levels less than those required to protect conductors from damage through the operation of a supply circuit overcurrent device. (CMP-5)

see 210.13, 215.10, 230.95 for examples of use

Ground Fault Protection of Equipment is different than just ground fault protection, a ground fault is often a short-circuit when using a grounded electrical system. The motor is likely already inherently bonded to the electrical system ground just through piping and other associated material, without pulling an equipment grounding conductor.​