We are installing an 40 KVA 230V 3 Phase 3 Wire emergency generator with an Automatic Transfer switch. The transfer switch, service entrance disconnect and meter base are set on a pedestal approx 30' away from emergency gen. We have installed our ground rods as required at the main service disconnect. We have installed ground rods at the emergency gen. Should we be tieing the service disconnect grounding to the emerg. gen ground rods? Should we have a grounding conductor running from emerg gen to transfer switch? We have a 20 Amp single phase breaker feeding off the main service to a block heater and batter charger on the emerg gen system. What do we do about the grounding conductor for that breaker?
Seperately Derived System
- Thread starter pjkc
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websparky
Senior Member
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- Cleveland, Ohio
Re: Seperately Derived System
Please look at NEC 2002 250.30 Grounding Separately Derived Alternating-Current Systems.
Most all of your questions will be answered here and throughout Article 250 and 230.
Please look at NEC 2002 250.30 Grounding Separately Derived Alternating-Current Systems.
Most all of your questions will be answered here and throughout Article 250 and 230.
Re: Seperately Derived System
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.
I hope that helps.
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Tom
How many poles is the transfer switch? Does it transfer the Grounded Conductor [Neutral] of the generator winding?
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.
Assuming that you are asking about an Equipment Grounding Conductor [EGC] the answer depends on whether the transfer switch transfers the Grounded Conductor [Neutral].
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
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