Fire Pump System

[dnbob]

We are wiring a new building with a fire pump.

The Service entrance conductors to the combination fire pump controller/ATS come from the utility transformer.
This firepump is backed up by a generator which serves other loads in the building. The fire pump circuit breaker is isolated from the other breakers in the generator.

My question is on the grounding/bonding. We are not switching the neutral on the other transfer switches in the building, so the bonding jumper is removed in the generator.

Next to the fire pump breaker in the generator there is a second bonding jumper and the question is do we need to pull a grounded conductor and no grounding conductor from the generator to the fire pump controller/ATS, or can we remove the bonding jumper at the generator and just utilize an equipment grounding conductor.

We installed a grounded conductor from the utility transformer. to the ATS/controller.

Thanks in advance for the help.

Bob

 

[Canton]

We are wiring a new building with a fire pump.

The Service entrance conductors to the combination fire pump controller/ATS come from the utility transformer.
This firepump is backed up by a generator which serves other loads in the building. The fire pump circuit breaker is isolated from the other breakers in the generator.

My question is on the grounding/bonding. We are not switching the neutral on the other transfer switches in the building, so the bonding jumper is removed in the generator.

Next to the fire pump breaker in the generator there is a second bonding jumper and the question is do we need to pull a grounded conductor and no grounding conductor from the generator to the fire pump controller/ATS, or can we remove the bonding jumper at the generator and just utilize an equipment grounding conductor.

We installed a grounded conductor from the utility transformer. to the ATS/controller.

Thanks in advance for the help.

Bob

For your setup there should not be a neutral/ground bond in your generator. You should have your 3 phases and ground going to the fire pump ats. From your utility transformer you should have your 3 phases and neutral going to the fire pump ats. Bond your neutral at the fire pump disconnect ats along with your GEC's there.

 

[dnbob]

Thank You.

That is how I have it wired, but was wondering/second guessing myself, how the breaker would trip in a ground fault on that feeder.

The ground and neutral would actually be connected via the bonding jumper in my main service.

Bob

 

[Canton]

Thank You.

That is how I have it wired, but was wondering/second guessing myself, how the breaker would trip in a ground fault on that feeder.

The ground and neutral would actually be connected via the bonding jumper in my main service.

Bob

Yes, if you had a fault at the generator from a phase to ground, your fault current path (one of them) would be on an EGC of a feeder to your Ats to your gear across your MBJ and the onto the neutrals going back to the generator. Could be a long route, depending on the design.