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3 phase panel on 1 phase service #111559 01/04/07 03:08 PM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline OP
Cat Servant
Chad Fabry, a home inspector, came across this darling:

[Linked Image]

Now, I wonder ... with electricity flowing "out" one half of the breaker, and "in" the other, is the electromagnetic part of the breaker made inoperable?

2017 / 2014 NEC & Related Books and Study Guides
Re: 3 phase panel on 1 phase service #111560 01/04/07 03:22 PM
Joined: Dec 2005
Posts: 152
Ann Brush Offline
What a gem! Depending on the slot you used for each SP breaker you could get 0 or 120V and for each DP breaker you could get 120 or 240V (to neutral), really great piece of work - love how the L1 and L2 lines are beautifully numbered, then hacked into a 3-ph panel.

Re: 3 phase panel on 1 phase service #111561 01/04/07 03:45 PM
Joined: Jul 2006
Posts: 272
Luketrician Offline
So this wasn't existing was it? Seems that there would be a definite balancing issue for the neutral conductors on most, if not all mwbc's. Another good example of someone knowing just enough to be dangerous.


Luke Clarke
Electrical Planner for TVA.

Re: 3 phase panel on 1 phase service #111562 01/04/07 08:47 PM
Joined: Oct 2006
Posts: 65
JohnJ0906 Offline
Is that rust on the neutral lug? (top right corner)

Re: 3 phase panel on 1 phase service #111563 01/04/07 09:11 PM
Joined: Nov 2002
Posts: 790
wa2ise Offline
Seems that if someone was to backfeed the 100 amp breakers as a main, they could have just tied the 3rd bus lug to 2nd bus lug. (Far as I can see, there's nothing on the bus lugs). Or just take the sltrsfy live output of the 70 amp breaker and loop that up to the 3rd bus lug. Would that make it a sub-panel imbedded in the main panel? [Linked Image] Not that that matters, this all violates code....

Re: 3 phase panel on 1 phase service #111564 01/04/07 09:43 PM
Joined: Sep 2002
Posts: 908
NORCAL Offline
Only one close to that is one I worked on where they had fed a 3 phase panel from a single phase tranformer and jumpering from center lug to right hand lug whole thing was a blooming mess.Another comment, seeing that is a I-T-E panel was jumper still in place on the split neutral? I am assuming its a sub not a main panel, otherwise grounding and grounded are bonded.

Re: 3 phase panel on 1 phase service #111565 01/04/07 10:58 PM
Joined: Jun 2004
Posts: 1,273
Tesla Offline
The installer missed the obvious jumper location: at the bus lugs at the top, still unused.

Our man has jumpered A and C phases ( Black and Blue )

Putting '#2' at position #3 is too cute.

Said jumpering will not produce any single pole breaker with a voltage of 0. All will show full voltage.

Double pole breakers will only show 0 volts when tapping Black and Blue. Red/Blue and Black/Red combinations will deliver full voltage.

Such a set-up makes one think that the panel was boosted from a commercial job way back when. The price difference would always stop a legitimate player from wasting a three phase panel so.

Alternately, it's a second hand panel rigged up by a tradesman. Still, a waste of value.

Re: 3 phase panel on 1 phase service #111566 01/05/07 09:42 AM
Joined: Nov 2001
Posts: 745
mamills Offline
Though this is certainly among the least of the problems here, isn't that 100a "main" breaker supposed to be fitted with some type of retaining screw if it is to be backfed like that (in any kind of panel)?

In one case, I saw a three phase panel being fed by a single phase service. The "C" buss was not being used at all - the breakers were located only on "A" and "B". Still not right, but at least someone was thinking about the neutral balancing issue. regrettably, the cover had long since disappeared, so it was all too easy to view the interior [Linked Image].

Mike (mamills)

[This message has been edited by mamills (edited 01-05-2007).]

Re: 3 phase panel on 1 phase service #111567 01/07/07 02:33 PM
Joined: Feb 2001
Posts: 54
tajoch Offline
A couple of years ago I was house hunting and saw one just like this, 3ph panel on a single phase service. They just didn't have any breakers in place on C phase.......
If one panel wasn't bad enough, there was a 3ph subpanel in the utility room........

Re: 3 phase panel on 1 phase service #111568 01/08/07 09:29 PM
Joined: Feb 2003
Posts: 288
yaktx Offline
I found (and corrected) one of these in an old warehouse, where an existing 240V delta had been rewired for 120/240.

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