# Is Neutral/Grounding Required for 3P Main lug for 3P only load



## HertzHound (Jan 22, 2019)

When you say “Main lug”, is that a sub panel off of the service, or is the service a main lug panel with six or less breakers? 

If the “Main lug” is a sub panel with a wiring method that qualifies as an equipment ground, then it is fine not to have a grounded conductor (Neutral) and an equipment grounding conductor. 

A service always needs a Neutral brought to it and grounded with the grounding electrode system, whether a load needs a neutral or not. A sub panel does not need a neutral conductor if there is only going to be three phase loads. It will need an equipment ground, but that may be the conduit. 

Just curious what the load is. If I had to guess, is it solar?


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## Southeast Power (Jan 18, 2009)

That specific plug is 4 wire.










It needs a ground wire.
What makes it so difficult to install a ground wire?
Get a ground bar and install it to the enclosure of the 400amp panelboard.
The key to this installation is the word EMT.
I Wouldnt expect to find a ground wire in an older EMT installation.
Just check to see if you have 120/208/120 to ground. If not, we will need to have a corner ground discussion.:wink:

If your Pin and Sleeve plug isn't rated as a disconnect, Install a cheap 60 amp disconnect for it:









One more thing.
The term " Grandfathered in" is nice but, what you have, when you wake up Grandpa, is what we call an "ongoing" violation.


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## splatz (May 23, 2015)

This just came up on another post. Some pin and sleeve receptacles are in and of themselves a disconnect, but if a lockable disconnect is needed, that's another question. 

You didn't say what these receptacles will be supplying but it's likely code will require a disconnect close to / within sight of the receptacles and equipment. OSHA requirements / safety policies may make it necessary too. For what the small lockable disconnects cost, I couldn't see not installing them at each receptacle, even without the code requirements. 

As for the questions regarding the need for a neutral on your 3-phase delta distribution and grounding conductor in 3/4" EMT and grandfathering- all due respect, I think you ought to bring in some help here, the in-person for-money type, not the post on the internet type. It's not that they are difficult questions but the one you worry about is the question you don't ask.


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## HertzHound (Jan 22, 2019)

I guess I didn't see the part about the pin and sleeve connection. I was thinking it was a line of solar inverters. Not that your question was bizarre, but solar guys do ask some strange questions. And because Solar is a separately derived system, it may explain why someone would be thinking about requiring a neutral, a ground, and an AC disconnect.


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## paulengr (Oct 8, 2017)

“Grandfathered” applies to replacement. As in my grandfathers house was wired originally with 2 blade receptacles so if you could find one at an antique dealer you could replace an existing one. When you install new equipment you follow current Code. So at that point in his house I’d have to pull new wiring (with a ground) to replace it with modern 3 blade receptacles, and the tamper resistant kind, and maybe an AFCI which probably means the Edison screw in fuse panel has to go, too, including the pennies under the fuses!

Same on your case. Also at 480 at least the grounded neutral is not mandatory but I can’t remember if it is or isn’t at 240...seems like it is. Either way bonding is mandatory so at a bare minimum you need a ground regardless of whether or not you need a neutral at the loads. Sometimes I see other arrangements for the ground. We have a breaker tester and a dry ice blaster. Both have a separate ground clip.


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## Bird dog (Oct 27, 2015)

Southeast Power said:


> If not, we will need to have a corner ground discussion.:wink:
> 
> One more thing.
> The term " Grandfathered in" is nice but, what you have, when you wake up Grandpa, is what we call an "ongoing" violation.





splatz said:


> As for the questions regarding the need for a neutral on your 3-phase delta distribution and grounding conductor in 3/4" EMT and grandfathering- all due respect, I think you ought to bring in some help here, the in-person for-money type, not the post on the internet type. It's not that they are difficult questions but the one you worry about is the question you don't ask.



Splatz is right. You need to talk to an electrical contractor. This sounds like an old system that you need professional help with. It sounds like you have a floating delta & Southeast Power would be right about discussing Delta xfmr connections.


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## [email protected] (Jan 12, 2020)

Thank you @splatz for your inputs!
The existing panel is being grounded through EMT and we were told that is no longer accepted due to a code change in 2018 in our area.. In house electrician believes it is perfectly fine though. We are basically getting conflicting answers from vendors. 

The load is not machinery or motors. They are PDUs with separate built-in breakers for each leg.


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## HertzHound (Jan 22, 2019)

It may not be floating. That’s the reason for bringing the neutral conductor to the service. After that it’s not required. Usually with a delta you would only run the neutral to a single phase sub panel, using A and C phase. A power panel would get the three phase without the neutral. 

As for a wire equipment grounding conductor, probably not needed if it’s metallic conduit. Over 250 volts to ground you would need bonding jumpers. But if it’s not the service, there’s so many exceptions that just two locknuts or an EMT connector with one locknut is sufficient. 

Have someone check it out. You probably want to pull an equipment ground with your new stuff, and just put a ground bar in the old sub panel cabinet to terminate it. If the sub panel is close enough, pull a #3 copper equipment ground back to the service. The conduit is big enough, but maybe impossible with a few bends. Maybe pull one of the 4/0s out, and drag a 1/4” rope in with it. Attach a ground and pull them back in.

Edit: my response was before the post above was posted.


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## [email protected] (Jan 12, 2020)

HertzHound said:


> When you say “Main lug”, is that a sub panel off of the service, or is the service a main lug panel with six or less breakers?
> 
> If the “Main lug” is a sub panel with a wiring method that qualifies as an equipment ground, then it is fine not to have a grounded conductor (Neutral) and an equipment grounding conductor.
> 
> ...


Thank you very much for your inputs @HertzHound !!


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## Kevin (Feb 14, 2017)

paulengr said:


> “Grandfathered” applies to replacement. As in my grandfathers house was wired originally with 2 blade receptacles so if you could find one at an antique dealer you could replace an existing one. When you install new equipment you follow current Code. So at that point in his house I’d have to pull new wiring (with a ground) to replace it with modern 3 blade receptacles, and the tamper resistant kind, and maybe an AFCI which probably means the Edison screw in fuse panel has to go, too, including the pennies under the fuses!


I'm just gonna leave this here...

Sent from my new phone. Autocorrect may have changed stuff.


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