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#84665 - 04/18/03 05:24 PM 1 phase system 3 phase panel
Steve T Offline

Registered: 02/14/01
Posts: 312
Loc: Oak Park, IL, USA
I had a contractor install a 3 phase panel for a single phase system.

He installed a 2-pole breaker which landed on bus B and C and then installed a wire from one terminal of the breaker to the other which in essence made phase C in the panel phase B. The phase arrangement was then A, B, B, A, B, B, etc.

He then proceeded to fill most of the breaker spots with 1-pole breakers but some had 2 pole. He did make sure to put the 2-pole breakers where he landed on both legs of the single phase service.

I see nothing in the code that specifically disallows a 3 phase panel on a single phase service, but since he could not show me which neutrals went with which hots (not to mention this is the most unorthodox installation I've ever seen) I told him to install a single-phase panel.

Any input on code violations on this type of installation would be helpful.

I do know about 110.3 but what does "considerations such as the following shall be evaluated" mean exactly?

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#84666 - 04/18/03 06:34 PM Re: 1 phase system 3 phase panel
Redsy Offline

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
Installing a 3 phase panel on a single phase system is a clear violation of 110.3.
The title says it all--
"Examination, Identification, Installation and Use" That is all you should need to say to him.
But, try 110.3 (A) (7) specific use, and 110.3 (A) (8) practical safeguarding. What if someone ran a multiwire circuit off of the same phase?
110.3 (B) seems pretty clear, also.

Another cheapskate attempt to save a few bucks!

#84667 - 04/18/03 06:48 PM Re: 1 phase system 3 phase panel
HotLine1 Offline


Registered: 04/03/02
Posts: 6832
Loc: Brick, NJ USA
Hey guys,
Had one about a year ago...
Comm bldg, HVAC unit at rooftop being relocated. Electrician locates panel...turns off two pole CB marked HVAC unit #x...goes back up to roof, opens disco.. finds disco is 3 pole....and 1 leg is "hot" to ground. Goes back down to panel..finds "single phase panel" with 3 phase feeder. The clown who put it in used the neutral block for the third phase leg!!

Now imagine some "unqualified" person, or some sparky in a hurry....disaster in the making.

Attempted to track down the culprit on general principles, but the trail dead ended cause there was no permit, no inspections, and the tenant paid "cash"!!

BTW, we were there working for the landlord, and yes, we did correct it.

#84668 - 04/18/03 08:30 PM Re: 1 phase system 3 phase panel
frenchelectrican Offline


Registered: 02/06/03
Posts: 938
Loc: Wi/ Paris France { France for ...
wow that is disgusting if any inspecter see that they will redtag it fast i have few scary experance too about not poper marking boxes especally with corner grounded delta system it was hair rasing event one box i see it it have all three phase condters came in but instering twist the corner phase was with main buss!! and it was hard to indentify it but took me a min to figure it out and i told the client that where is the nuetural line ?? he say on the buss and i look at breaker box again and i was shocked to see how it set up i told him that i will call the inspecter to redtagged him fast then he offered me to fix it right and converted from delta to wye system and slove the grounding issues

merci marc
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

#84669 - 04/20/03 08:44 AM Re: 1 phase system 3 phase panel
Steve T Offline

Registered: 02/14/01
Posts: 312
Loc: Oak Park, IL, USA
I was trying to explain to him about another electrician doing just that--not to mention he appeared to have landed a multi-wire circuit on the same phase. I tried to explain to him about the dangers of overcurrent on the neutral but he didn't get it or didn't care. Either way, I now have a red flag on his file and this contractor will need to submit detailed plans for any work he does, no matter how simple. I ultimately hope this keeps him out of my town.

#84670 - 04/24/03 07:29 PM Re: 1 phase system 3 phase panel
ZackDitner Offline

Registered: 10/11/02
Posts: 46
Loc: Kitchener, Ontario, Canada
Well jeez, so thats the "real" reason there is that green neutral bus bonding screw, so you can use it as a neutral in a main, or as a hot when you remove the bonding screw.. haha

In regard to the first topic, you're point about a 2pole breaker being able to be on the same phase if you used a 3ph panel on a single ph service, well some single phase panels can have a 2pole breaker installed and it will be on the same leg for each pole...

i'm not saying using a 3ph panel on a single phase is right in any way though.

I've seen a picture if it done though, doubled up wires on phase "B" for a jumper to phase "C", in fact i think there was a pic of it on the violations forum here many moons ago.

#84671 - 04/25/03 05:30 AM Re: 1 phase system 3 phase panel
sparky806 Offline

Registered: 12/07/02
Posts: 59
Loc: Shawnee, KS, USA
I used a 3 phase panel in my garage. A and B phases are hot, but C phase is bonded to ground, filler plates glued over all C phase spaces. AHJ had no problems with it.

#84672 - 04/25/03 04:46 PM Re: 1 phase system 3 phase panel
spyder Offline

Registered: 10/14/02
Posts: 211
Loc: Massachusetts
The equipment is not being used for whats its listed and labled for and thereore a violation.


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