Switching neutrals or not

[Dbarrett]

I know this has already been brought up in the past but how do you guys feel about switching Neutrals in the knifeswitch? I don’t see it necessary but I did find that 690.15(d)
It states: Equipment Disconnecting Means. An equipment disconnecting means shall simultaneously disconnect all current- carrying conductors that are not solidly grounded. I know that 404.2(b) states otherwise. Thoughts?


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[ggunn]

I know this has already been brought up in the past but how do you guys feel about switching Neutrals in the knifeswitch? I don’t see it necessary but I did find that 690.15(d)
It states: Equipment Disconnecting Means. An equipment disconnecting means shall simultaneously disconnect all current- carrying conductors that are not solidly grounded. I know that 404.2(b) states otherwise. Thoughts?


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Read them again; they say the same thing. Don't switch the neutral.

 

[Dbarrett]

The neutral isn’t a current carrying conductor?


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[ggunn]

The neutral isn’t a current carrying conductor?


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..."disconnect all current- carrying conductors that are not solidly grounded."

It's solidly grounded.

 

[texie]

And if it is a fusible switch you can not switch the neutral anyway. While in some cases the code requires switching a grounded conductor, is very rare and there could not be a fuse.

 

[augie47]

The neutral isn’t a current carrying conductor?


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?

If there is a load connected,the neutral carries current !

 

[LarryFine]

The neutral may be switched, as long as all non-grounded conductors are simultaneously opened, but may not be individually fused.

 

[GoldDigger]

The neutral may be switched, as long as all non-grounded conductors are simultaneously opened, but may not be individually fused.

And in certain cases, like a transfer switch from a service to a non-SDS generator installation, the neutral must be switched along with the hot conductors. Such transfer switches often incorporate a time offset so that the neutral is broken after the hot conductors and makes the new connection before the new hot conductors are switched in. This avoids even momentary operation of MWBCs with an open neutral.

 

[jaggedben]

For a run-of-the-mill AC side disconnect for a solar inverter, there is no reason whatsoever to switch the neutral, and it's generally prohibited.

 

[Dbarrett]

I agree that it shouldn’t be disconnected, it’s just how my company chooses to install things. Just wanted to get a majority feedback. Why prohibited?


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[texie]

I agree that it shouldn’t be disconnected, it’s just how my company chooses to install things. Just wanted to get a majority feedback. Why prohibited?


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See NEC 240.22

 

[pv_n00b]

I agree that it shouldn’t be disconnected, it’s just how my company chooses to install things. Just wanted to get a majority feedback. Why prohibited?

You don't want to create an ungrounded system where the NEC requires system grounding. For grid-tied inverters that shut down when disconnected, this is not an issue. If you have a multimode inverter that continues to provide power after being disconnected then an alternate way to ground the grounded conductor would be needed if it was disconnected from the bond in the service entrance.