How long can the conductors be to a firre pump?

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merleh

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I have a question about the NEC. I will be feeding a fire pump controller from a new transformer that is remote from a building. I understand that I cannot put overcurrent protection on the secondary side of the transformer. This gives me a 90' run from the transformer to the overcurrent protection which is at the fire pump controller. How far can this run be?

The relevant code sections:

695.5(B) Prohibits overcurrent protection on the secondary before the fire pump controller.

240.4 (F) Informs me that the wires on the secondary side of my delta-wye transformer cannot be assumed to be protected by the primary fuses.

Okay, so that seems to indicate that I have a section of conductors that are protected only by the fuses at the controller (on the load side of the conductors). That naturally brings me to section 240.21. Here I get stuck.

240.21(B)(5) seems to say my conductors can be unlimited outside the building. But I cannot use this rule because it requires that the conductors must end at a single circuit breaker or fuse. (I feed two sets of overcurrent protection, the main pump and the jockey pump.) Further, I would need to locate my controller where the conductors enter the building, which is physically impossible.

I seem to be ending up at 240.21(B)(1) which limits me to 10 foot total conductor length. That is way too short.

Can anybody help me? I would love to hear your comments.
 
Re: How long can the conductors be to a firre pump?

Merleh
The service to a fire pump is a special case in the code.
The conductors are not protected from overload
as stated in 695.6D. The conductors are size to
125% of the fire equipment load but the primary fuse of your transformer is sized to handle the lock rotor load of the equipment. It is more important to have the pump run until failure rather that have the water supply interrupted.
 
Re: How long can the conductors be to a firre pump?

Is the transformer dedicated to the fire pump? (does it run the fire pump only?) If not, you can have one disconnect in the building.

Also, you can run your feeder anywhere inside the building if you encase the conduit in 2" of concrete. See 695.6.

Steve
 
Re: How long can the conductors be to a firre pump?

Bob,

Thanks for the reply. It was quite helpful.

Yes, I was aware that the fire pump service was special, but I wasn't sure if 240.21 applied. I looked again at 695.6(D) as you suggested and found my answer, "The applicable distance and size retrictions of 240.21 shall not apply." It would have been nice if there had been a fine print note at 240.21 mentioning this exception.

Thanks for the help.
 
Re: How long can the conductors be to a firre pump?

Steve

Thanks for the reply.

Yes, the new transformer is dedicated to the fire pump and jockey pump.

Yes, I see that the service conduit inside the pumproom needs to follow 695.6(A), which says the conduit must follow 230.6(1) or 230.6(2), which requires 2" concrete. Since my controller is located about 20' from the wall, I will need to either enclose that conduit in concrete or run it under the floor.

Thank you for the help.
 
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