Sub Panel Wiring

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frank_n

frank_n

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Central NJ
I was in a home today that had a 3-wire sub-panel wired for 120 volts. The HO ran a wire from one leg of the main breaker to the other.

I know this is illegal, but I cannot find a code reference. Anybody know what code(s) prohibit this?

Frank
 
frank_n said:
I was in a home today that had a 3-wire sub-panel wired for 120 volts. The HO ran a wire from one leg of the main breaker to the other.

I know this is illegal, but I cannot find a code reference. Anybody know what code(s) prohibit this?

Frank
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from one leg of the main breaker to the other? other leg of the main? That would be a direct short.
 
steelersman said:
from one leg of the main breaker to the other? other leg of the main? That would be a direct short.
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I need to explain it better. He ran a 120 volt circuit. From the breaker in the main panel to Phase A on the main breaker on the sub. Then a wire from Phase A to Phase B on the sub. Both phases on the subpanel are on the same breaker on the main panel. I hope that was more clear.
 
frank_n said:
I need to explain it better. He ran a 120 volt circuit. From the breaker in the main panel to Phase A on the main breaker on the sub. Then a wire from Phase A to Phase B on the sub. Both phases on the subpanel are on the same breaker on the main panel. I hope that was more clear.
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That's weird. Why would someone do that? I'd get rid of it. So is there 2 wires coming off the same lug on the main and going to sub-panels A leg and the other wire to B leg, or is it just one wire off the main to sub-panel's A leg and a short jumper from that same A leg to the B leg?
 
steelersman said:
quote: "a wire from one leg of the main breaker to the other."

To me that sounds like a jumper wire and a direct short. I know that's probably not what it really is but....
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It's not 120/240, it's 120 only. The same hot wire heats up both bus bars.


frank n:
The reason you can't find it in the Code book is because it isn't there.
 
steelersman said:
quote: "a wire from one leg of the main breaker to the other."

To me that sounds like a jumper wire and a direct short. I know that's probably not what it really is but....
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Its not a direct short b/c he only has one phase in the subpanel to begin with.

edit: just read the other posts, sorry
 
I pondered whether or not that was legal at one point. A lot of old apartments around here have no separate ground wire and would be very very difficult to get new lines to and I always wondered if you were to ever switch those out if you could just recolor one leg and make it white. Lots of times they have gas ovens and no electric heat. The only issues I could think of were that the wire shouldn't be reidentified to white being that it's smaller than 6 and that you would have to make sure to stagger the legs in every apartment so that you didn't just load up th eone side
 
William1978 said:
Is the lug for phase A in the sub panel approved for two wires?
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Probably not but, a wire nut and two pigtails would solve that.

Roger
 
steelersman said:
quote: "a wire from one leg of the main breaker to the other."

To me that sounds like a jumper wire and a direct short. I know that's probably not what it really is but....
Click to expand...

Sorry, but I thought you missed this part.

was in a home today that had a 3-wire sub-panel wired for 120 volts.
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And I'm only a dog, so I don't have that much brain power. :roll: :grin:
 
SiddMartin said:
Its not a direct short b/c he only has one phase in the subpanel to begin with.

edit: just read the other posts, sorry
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well when he said: "a wire from one leg of the main breaker to the other". I thought he meant the main breaker in the main panel. I didn't realize the sub panel had a main breaker in it. mine usually don't.
 
If the lug is rated for 2 wires no issue, imo, otherwise you could splice the wires and have one wire under each lug.

Some PV panels only supply 120V so you have a similar situation. The last One I did I just used the "A" phase with no breakers on the "B" phase and no jumper.
 
Dennis Alwon said:
If the lug is rated for 2 wires no issue, imo, otherwise you could splice the wires and have one wire under each lug.

Some PV panels only supply 120V so you have a similar situation. The last One I did I just used the "A" phase with no breakers on the "B" phase and no jumper.
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What's a PV panel?
 
I still run into an occasional 120v-only resi service. Triplex is dropped to the house, but one hot is folded back and taped off.

If there's a panel, it's jumpered from one lug to the other.
 
I run into this every now and then in an old house old 120v services that is.. the meters were 120v meters. But if you install a panel with an A and B phase and jump out the 2 phases isn't that not the intent for the panel use. So wouldn't that violate the UL listing? Wouldn't that put it in violation
 
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