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Inverter System AC Breakers

Inverter System AC Breakers

Inverter System AC Breakers

(OP)
We're replacing a legacy protected AC system that uses two pole breakers for all 120V circuits (they interrupt the neutral). We suspect the original motor-generator set was ungrounded and the neutral was interrupted to allow ground isolation but the new system will be grounded. Is there any reason to run the neutral through a breaker pole in a grounded inverter system?

RE: Inverter System AC Breakers

Where are you? If you are in the US, you are not allowed to break the neutral circuit if it is grounded.


"Will work for salami"

RE: Inverter System AC Breakers

mls1 - no reason to run the neutral through a breaker pole if your neutral is grounded, but no reason not to either. jraef is wrong about you not being allowed to break the neutral if it is grounded. You can break a grounded circuit conductor as long as you simultaneously break all of the associated hot conductors with the same breaker operation (NEC 240.22)

xnuke
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RE: Inverter System AC Breakers

(OP)
Thanks for the replies. Yes, I am in the USA. The new system will have redundant inverter systems so I believe I will need to bond the neutral to ground at the inverter and run the neutral through a pole in the main breaker of the distribution panels that can be fed from either (not both) sources since they are separately derived. After that, I don't see any need to run the neutrals through breaker poles on downstream feeders or branch circuits and would prefer not to as it would just take panel space that I don't want to use. The only reason I could ever see doing this is if we were to run ungrounded I'd need to open the neutral to provide ground isolation. If there are other thoughts I'd appreciate the comments.

RE: Inverter System AC Breakers

I prefer to follow the KISS principle. Keep It Simple, Sam. Tie all the neutrals together solidly unless protection issues and possible ground fault detection issues force you to switch the neutrals. Even with ground fault protection it is often possible to use solidly connected neutrals. You May have to use more than one CT and/or protection relay. That may be cheaper than the possible damage in the event that a transfer switch or breaker contact fails and leaves you with an open neutral.

Bill
--------------------
"Why not the best?"
Jimmy Carter

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