3 Phase Panel, With No Neutral Project.

CNC

I just got back from helping a guy i work for, look at a job. Its not my job, i was just there to help look at it, because im going to work for him if he gets the bid. I noticed a few things i wasn't familiar with how to handle them, or if the way he wants to go about it is correct, and i wanted to check here, before i started checking specific codes.


Its a winery where the owner wants some additional circuits added for some large 3 phase loads. While looking at the panels, and trying to see what space is left in the panels. There isnt much. BUT he found some existing large circuits going out of the electrical room that had been disconnected because they used to supply power to huge refrigerator units, because the building used to be a giant freezer back in the day. they are tapped with the rest of the panel feeds in a gutter, and then supply a feed thru breaker (which they disconnected and just capped it all off when the unit were removed. He is thinking about using the 1 1/2 rigid, and the existing conductors to feed a new three phase panel, everything looks great, and thats not a problem. BUT there are only 3 - 1 awg conductors in the pipe. its a long run, and it ends in a perfect spot for the new panel, and will only need a 100 amp panel, ( a few 30a 3 phase loads is all they will take out of the panel)


NOW this is my question, he cant use the 1 1/2 rigid as his ground can he? can he set a panel with no neutral and only for 3 phase loads? I wanted to pull the wire out, and use the existing pipe but pull the correct conductors, with a ground. HE insists its much to long and this is fine and will save money. If he cant use the rigid would a ground rod suffice for a sub panel.

Sorry for the long winded question.

ltcox

I can't speak to the specifics of the installation but can give a general opinion.
Of the three types of conductors: ungrounded (phase), grounded (neutral) and grounding (ground) it is permissible to run just ungrounded conductors with a phase-to-phase load. The panel cannot feed any line-to-neutral loads.
It is also allowed that the GRS conduit be used as the "grounding" means.
With proper grounding it is seldom advisable to add a ground rod. My experience has been that older, previous use facilities have problems with bonding the grounded conductor in all the wrong places.

Magnettica

344.60 Grounding. RMC shall be permitted as an equipment grounding conductor.

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Bkessler

There is nothing that says a panel has to have a grounded conductor.

JohnJ0906

If the rigid is continuous, it can be used as the EGC. A ground rod is NEVER able to be used as a EGC.

A ground rod is a grounding electrode, not a fault path.

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John from Baltimore
"One Day at a Time"
All replies based on the 2008 NEC

CNC

I thought so, grounding is something i myself have not completely grasped every concept. I have read A lot of mike holts stuff , and need to read more. This commercial retrofit stuff is not my typical work. IF the rigid hit a large junction box, would bushing a proper size ground wire, bonding the rigid comply?

JohnJ0906

Mike's "Grounding versus Bonding" is a very good book, imo.

There is a lot of confusion about the various requirements, and I am not always sure myself...

If the rigid is wrench tight, and there are continuous metal connections/boxes, and no concentric/eccentric KOs, you should be good.

I wonder if there is a good way to test the resistance of a conduit like this?

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John from Baltimore
"One Day at a Time"
All replies based on the 2008 NEC

CNC

being the age of this building, and that there is some buried in the concrete, it sounds like it would be a very good idea. That was the issue with just pulling the conductors. If it were my job id handle it a bit differently. i thought id run it past you guys, they sound like stupid questions, sorry. Its the retrofit stuff, and not being able to plan it from the start, that i start to question decisions.

Great idea, i should purchase some of the mike holt stuff, its the ground rods people have told me mixed things, or just mixed me up on their uses, using them when they wont do anything. (I used to work with a guy who liked to pound them for hot tubs, when their was ALWAYS a properly sized EGC going to the service) does that do anything?