Opening control panel neutral

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jroushdi

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Control panel has 120VAC feed. Is it a violation to use a 2-pole main disconnect and open the neutral as well as the ungrounded conductor to de-energize the panel for maintenance? The panel, of course, has an equipment ground. This issue arose because there is an ungrounded 24VDC power supply in the panel and the vendor says that the neutral should be disconnected. The panel feeds PLC I/O field devices that have no multi-circuit connections, etc.

Any input is appreciated. Thanks.
JR
 
I do not belive it is a violation, as long as both wires from the circuit are simulataneously disconnected. However, I am suspicion of the techs comments. I have never worked on PLC's so I am curious what others have to say.
 
jroushdi said:
...the vendor says that the neutral should be disconnected. ...
Click to expand...
A vendor would be the company which sold the equipment. Is it the manufacturer, also? It makes a big difference here :)

Personally, I don't see how the ungrounded 24VDC supply has anything to do with it. I've worked on plenty of PLC-controlled equipment and have never seen grounded supply conductors switched open by the disconnecting means... but then again, I can't explicitly recall working with any equipment that was supplied by 120VAC :rolleyes:
 
Yes, the mfg., Lambda Power Supplies. I think they're concerned about the 24VDC output floating when it should be de-energized but my experience is like the rest of you, I've never done it or seen it done.

THe 120V feed is because we feed nothing requiring greater voltage from the panel so no point increasing potential hazard with 208, 240, or 480 if we don't have to. Feeder voltage drop isn't a concern due to distance.

Thanks
 
There is nothing wrong with it, in fact at gas stations the NEC requires it. (514.11(A) 2008)

But for your equipment a couple of things.

1) It is likely outside the scope of the NEC

2) If it is under the NEC 240.22 allows it. :smile:
 
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