Art. 250.24 (C)

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Inspector Don

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Bowling Green Ky.
I'm requesting that the Electrical Contractor bring in a Grounded conductor for a 3ph 480 volt , Fire Pump Transfer Switch and Bond it to the enclosure ( Which is Marked for use as Service Equipment ) The Utility Supply is a 480/277 volt service. Is there a reason that the Electrical Engineer for the project is telling me that the Grounded conductor is not needed and therefore it is not required.
I'm I missing something , or is it just the Electrical Engineers way of thinking.

Thanks: Inspector Don
 
The engineer is simply saying that the fire pump itself does not require the neutral. It is possible that the engineer is right. But I would need more information. Several questions come to my mind:

(1) Is the power being brought to the fire pump a separate service from the utility?

(2) You said that the enclosure is marked for service equipment. That just means that the manufacture says that it can be used for that purpose. But is the enclosure actually being used as service equipment?

(3) The utility may have 480/277 available, and they may be bringing 480/277 to other locations within the same facility. But is the utility bringing 480/277 to the fire pump, or is it just bringing 480 to the fire pump?

(4) If the utility just brings 480 to the fire pump, and if that is a separate service from any other power that the utility is bringing to the facility, is the service grounded (i.e., does it come from a separate, ungrounded, 480V secondary?
 
Art 250.24 (C)

Art 250.24 (C)

Charle B. The Fire pump Transfer Switch is a Service that is being supplied by a utility transformer that alsos supplies the main structure. Which is a 480 / 277 volt system.
 
Then I think you are calling it correctly.

The fire pump might not need a neutral, but it will need an EGC. The neutral and ground must be bonded at the service disconnect, and no other place downstream. For the firepump's EGC to be able to carry fault current back to the source, it needs a path. That path is from the fire pump to the service disconnect enclosure, to the N-G bond at the enclosure, and along the service's neutral wire back to the utility transformer. If the neutral is not bonded to the enclosure, then this path is not complete.
 
Agreed. The system provides a neutral; it must be brought to the service disconnect, and bonded to the premises EGC via a main bonding jumper.
 
Think of the grounded conductor - neutral- as a white wire with a green stripe. Its isized either to carry the maximum unbalanced load as a neutral - white- or to carry fault current EGC - Green.
In this case its a green wire.
If you don't have it a line to case fault won't clear, there is no way for the fault current to return to its source.
It seems like many engineers don't understand this concept. I recently did a job 277/480 pump station with no neutral loads, I could not get the engineer to change the neutral size from 2 350 in parallel to a smaller size, per the green wire requirement.
 
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