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Old 11-09-2011, 07:42 AM   #1
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switched neutral (transfer switch)


Is there an easy to understand explanation of what is happening with a switched neutral on a single phase transfer switch?

Help appreciated.

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Old 11-09-2011, 08:40 AM   #2
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switched neutral (transfer switch)


The neutral as well as the hot line(s) is switched from the A side (say, utility power) to the B side (say, the generator feed).

Take a typical subpanel. The neutrals and grounds are kept separate within the subpanel but the neutral in the feed back to the main panel is bonded to ground up in the main panel. Let's suppose that the transfer switch serves the subpanel only.

With a transfer switch that does not switch the neutral (A side to the main panel, B side to the generator feed), the subpanel neutral remains bonded to ground via the main panel. With a transfer switch that does switch the neutral, when you switch to generator feed the subpanel neutral is unbonded from ground.

The switched neutral transfer switch is desirable for generators with built in GFCI protection so neutral current can't split up between the neutral and ground lines from the subject electrical system back to the generator, which would trip the GFCI's.

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Last edited by AllanJ; 11-09-2011 at 08:48 AM.
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Old 11-09-2011, 07:33 PM   #3
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switched neutral (transfer switch)


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Originally Posted by AllanJ View Post
[...]Let's suppose that the transfer switch serves the subpanel only.
I want to connect the the main breakers from the breaker box into the transfer switch without a subpanel. I guess that only leaves disconnecting the neutral from the ground in the generator?
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Old 11-09-2011, 08:46 PM   #4
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switched neutral (transfer switch)


Switch two hots...




Switch two hots and the neutral...

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Old 11-09-2011, 09:03 PM   #5
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switched neutral (transfer switch)


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Originally Posted by soma View Post
I want to connect the the main breakers from the breaker box into the transfer switch without a subpanel. I guess that only leaves disconnecting the neutral from the ground in the generator?
You can do that too with a switched neutral transfer switch.

But here the switched neutral transfer switch won't give you any benefit over a regular transfer switch unless you have (or rerun) 4 conductors up out of the main breaker box (hot, hot, separate neutral, ground) to the meter and you separate the neutrals and grounds in the breaker box.
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