Need for a gnd conductor

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So on your typical service entrance to a building (Between the utlity transformer and your switchboard) you always install three hots, one neutral, and one ground. I have never installed it that way. I would install 3 hots and a neutral. The grounding/bonding would take place in the switchbaord.
 
If you don't install a ground between the switchboard and transformer, why do I need a ground between the transformer and fire pump?
 
let's try this again. On you system, you need a fault return path in the event of a ground fault. That apth must go back to the source (transformer) for the overcurrent device to operate properly. On the load side of the service, that path is an equipment ground. It may be a conductor or any of the means listed in 250.118.
From the line side of the service equipment, thru the use of a bonding jumper, the fault path to the source (transformer) is the grounded conductor.
To some degree this is semantics...the same path is grounded (in your case neutral) conductor from the service to the transformer and equipment ground from equipment to the service means.
 
Ground

Ground

what gus said + since you're supplying a motor load you don't need a return wire (neutral) and you're using the grounded conductor as a ground fault path. As far as between the service and entrance to the building there's no use for a ground wire since you're bringing the grounded conductor (neutral) from the utility ground grid. From the service entrance (metering section + disconnect or what have you) the point is so that you bond the equipment ground to the neutral only at the service entrance (for each building). You don't want the the neutral to be bonded at more than one point so you dont lose your ground reference (aka not have parallel ground paths).
 
Thank you all very much for the assistance.

I think what I need to do (correct me if I am wrong) is to install a grounded (neutral) conductor in the conduit. This would be connected to the neutral lug in the transformer. On the fire pump side I will land the conductor under the ground lug. This would be the same as landing it on a neutral bar and bonding it IMO. To this same lug/bar I will drive a ground rod and install a conductor. I would then be treating this just like a normal service to a typical building.
 
You need a conductor to clear a line to case fault. For this application, on the utility side of the service its a white wire, on your side its a green wire.
Ground rods are not for fault clearing for this application
 
Most fire pump systems I have wired, have been strictly a 480 volt ungrounded delta with phase grounding monitors, this is because you want that fire pump not to quit at anytime, and not because of just one phase to ground short, also we always sized our service conductor at 125% of the FLA of all fire pump motors, and sized over current protection at full locked rotor current that will carry the lock rotor current forever. see 695 for these requirements (well except the ungrounded delta part, that was a local inspector requirement)

I would say you need to do some reading in article 695 because fire pumps are a very special system to wire, and is totally different from regular wiring, as far as over current goes.

This is because they want those pumps motors to not stop till they burn up.

I would ask the utility to just supply an ungrounded delta from the transformer, if that is what they supply then no need for the neutral or grounding conductor from it.

Also give the utility the lock rotor current of all pumps so they size there transformer to this and not just the expected load.
 
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shockin said:
Thank you all very much for the assistance.

I think what I need to do (correct me if I am wrong) is to install a grounded (neutral) conductor in the conduit. This would be connected to the neutral lug in the transformer. On the fire pump side I will land the conductor under the ground lug. This would be the same as landing it on a neutral bar and bonding it IMO. To this same lug/bar I will drive a ground rod and install a conductor. I would then be treating this just like a normal service to a typical building.
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Yeah, that sounds right now. Like you said, it becomes a regular service, so if there is a metal underground waterline, building steel, ufer, etc. use those too. NEC does not, as far as I know, make a distinction between regular waterline and fire protection water for the GES, but some other NFPA standards may, and you may not be allowed to use the fire protection line as a GEC, though the interior piping should be bonded. Check with your AHJ.

This is also subject to voltage drop considerations, so at 500' you need to think of that too. Your voltage cannot drop more than 15% at start-up (695.7).

As this is an additional service allowed by 230.2(A)(1), don't forget the plaques specified by 230.2(E).
 
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