Grounded conductors to and from a transfer switch.

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buddog57

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I am installing a 120/240 v transfer switch next to a service panel on a residence for the purpose of installing a standby generator.I am running the ungrounded conductors from a 100A two pole breaker in the service panel,to the transfer switch ,and back to the service panel to tie into the sub panel feeders,in the same conduit.I have sized the conductors to allow for derateing.
My question is,do I have to run the grounded/neutural conductor from the service panel to the transfer switch and back to the service panel (two conductors)? Or will one grounded/neutural conductor between the transfer switch and the service panel meet code requirements?
My understanding is that the two ungrounded conductors running from the service panel to the transfer switch,and the two ungrounded conductors running back from the transfer switch to service panel,in the same conduit,will cancel each others magnetic fields,and I should only need the grounded/neutural conductor when the utility power is cut off or by passed and the standby generator is feeding power to the residence.Am I correct?
Thankyou for your input,
Bob.

[ February 06, 2005, 01:31 PM: Message edited by: buddog57 ]
 
Re: Grounded conductors to and from a transfer switch.

It appears from your description that the grounded/neutural conductor will not be switched by the transfer switch.
That may or may not be acceptable. It depends on whether or not the generator neutral is bonded to it's frame.

Seems that the layout illustrated below would be simpler.

Ed

Transfer2.gif
 
Re: Grounded conductors to and from a transfer switch.

The grounded/neutral conductor is not being switched,and the neutral is not bonded to the generator frame as should be the case in a seperately derived system.
The home owner prefers to have whole house back up power available and the generator has been sized to the connected load.
Thanks in advance for any other responses.
Bob.

[ February 06, 2005, 03:09 PM: Message edited by: buddog57 ]
 
Re: Grounded conductors to and from a transfer switch.

If it's a seperately derived system then shouldn't the neutal be switched as well?
 
Re: Grounded conductors to and from a transfer switch.

ken987 - If it was a SDS, then yes, the "neutral" should be switched also.

But buddog57 says it is not a SDS.
 
Re: Grounded conductors to and from a transfer switch.

how do you get power from a seperate source, when it is not a seperately derived system? other than from just grabbing it from a different place in the same system through switching.
 
Re: Grounded conductors to and from a transfer switch.

Originally posted by bradleyelectric:
how do you get power from a seperate source, when it is not a seperately derived system? other than from just grabbing it from a different place in the same system through switching.
Click to expand...
It can only be SDS when the input and output are electrically isolated from each other. In the case of the generator it depends on what is being done with the grounded circuit conductor. If it is switched, then it is SDS, if not then no SDS exist.
 
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