Re: Seperately Derived System
We are installing an 40 KVA, 230V, 3 Phase, 3 Wire, emergency generator with an Automatic Transfer switch.
How many poles is the transfer switch? Does it transfer the Grounded Conductor [Neutral] of the generator winding?
The transfer switch, service entrance disconnect and meter base are set on a pedestal approx. 30' away from the emergency generator. We have installed our ground rods as required at the main service disconnect. We have installed ground rods at the emergency generator. Should we be tying the service disconnect grounding to the emergency generator ground rods?
The answer to this question is an unequivocal YES!
250.58 Common Grounding Electrode.
Where an ac system is connected to a grounding electrode in or at a building as specified in 250.24 and 250.32, the same electrode shall be used to ground conductor enclosures and equipment in or on that building. Where separate services supply a building and are required to be connected to a grounding electrode, the same grounding electrode shall be used.
Two or more grounding electrodes that are effectively bonded together shall be considered as a single grounding electrode system in this sense.
Should we have a grounding conductor running from emergency generator to transfer switch?
Assuming that you are asking about an Equipment Grounding Conductor [EGC] the answer depends on whether the transfer switch transfers the Grounded Conductor [Neutral].
We have a 20 Amp single phase breaker feeding off the main service to a block heater and battery charger on the emergency generator system. What do we do about the grounding conductor for that breaker?
That EGC must be run with the branch circuit conductors all the way to the block heater. No matter what you do with the two sets of electrodes and the bonding of the generator neutral the branch circuit EGC must be run with the circuit conductors for the block heater.
I hope that helps.
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Tom