K8MHZ
Senior Member
- Occupation
- Electrician
Multiwire circuits tripping because neutrals shared,(?) Main breaker installed wrong.
- Thread starter Mikros
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K8MHZ
Senior Member
- Occupation
- Electrician
I agree it's not logical, but I have seen it.
Again, take a look at my bad sketches. The 'jumpering' is done ahead of the sub-panel, but I have seen it in the panel, too.
- Location
- Massachusetts
K8MHZ
Senior Member
- Occupation
- Electrician
The OP didn't mention it, but that's the only way to feed a 120/240 panel and get all the breakers to have 120 volts.
I guess to clear things up, it would help to get the OP's input as to whether or not my sketches would be applicable.
- Location
- Massachusetts
Or, a ungrounded conductor is open and the OP is reading the same leg on both sides of the breaker due to reading through loads.
That is common, much more so than some sub-panel rigged for 120 volt only.
K8MHZ
Senior Member
- Occupation
- Electrician
To each their own, I am not buying into your jumper theory.
It's not my own, I think it's stupid, but I have seen it done in brand new construction of a power plant control building that had no 240 volt loads. I have also seen it in an old house that only had 120 coming in, but a nice new 100 amp breaker panel being fed from it, with the 'jumpering' being done from another panel ahead of the 100 amp panel.
The power company doesn't have to follow the 'rules'. The owner of the house did though, and the inspector had the power cut when he saw the cluster.
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K8MHZ
Senior Member
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- Electrician
I understand. but I don't read the OP's description the same way you do, obviously.
The 120 rigging is very uncommon. But it is done. Hopefully the OP will pop in and referee for us.
K8MHZ
Senior Member
- Occupation
- Electrician
One panel in the power plant was 120 only, fed with 3 4/0 conductors. Two for the 120 volt hot, same phase, same 'leg', same source, and one for the neutral.
I pointed out to one of the engineers that there may be an overloading issue on the neutral. He didn't care, and said the conductors were so oversized they would never see anything close to being fully loaded, anyway.
It was a main lug panel, wired like my first sketch.
I pointed out to one of the engineers that there may be an overloading issue on the neutral. He didn't care, and said the conductors were so oversized they would never see anything close to being fully loaded, anyway.
It was a main lug panel, wired like my first sketch.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
My reading of the OP is the same as Iwire's and why I asked.
It's based on what Iwire posted:
Now tell me why on a new (assumed) meter/main combo someone would "jumper" the legs since 240V is right there. The bus in a meter/main is the same as any other bus or panel. So I can't see how a 2-pole breaker could possibly pick up the same leg on both poles.
That aside, I also think (like Iwire) that there is an open either in the bus stab or the 60A breaker.
Also haven't seen where the OP has come back to "clear up" any confusion.:happyno:
It's based on what Iwire posted:
Originally Posted by Mikros
I have a Milbank meter/panel combo pedestal feeding a sub-panel. (240/120v 1-ph 3w)
In the Milbank pedestal panel, there is a 60A 2pole breaker that feeds a separate sub-panel next to it.
The 60A 2P breaker is installed in a position where the two poles are fed from the same leg in the Milbank panel. (so, 120v to ground on each pole, but basically zero volts between them)
Now tell me why on a new (assumed) meter/main combo someone would "jumper" the legs since 240V is right there. The bus in a meter/main is the same as any other bus or panel. So I can't see how a 2-pole breaker could possibly pick up the same leg on both poles.
That aside, I also think (like Iwire) that there is an open either in the bus stab or the 60A breaker.
Also haven't seen where the OP has come back to "clear up" any confusion.:happyno:
Sorry to leave you guys hanging
Sorry to leave you guys hanging
Hi all, sorry I haven't been back, a change in employment happened and I forgot about this. I am now working for another contractor and am having a slow day, logged in and saw this thread again.
The Milbank meter combo was a u5100-xl, or very similar. It is just a strange way that Milbank arranged the breaker bussing that allowed a two pole breaker to end up with both sides of it on the same feeding leg. (hope that makes sense) There was nothing modified or jumpered, but it would be easy not to notice if you just slapped the breaker in quick. I tried to find a cut sheet that shows the bussing but no luck.
http://www.milbankworks.com/specsheets/784572258785_SS.pdf if you look close you can see one of the breaker "stab" holes is empty in this very similar picture linked. I wonder if that is done to avoid the issue I ran into, maybe the one I worked on is older.
Sorry to leave you guys hanging
Hi all, sorry I haven't been back, a change in employment happened and I forgot about this. I am now working for another contractor and am having a slow day, logged in and saw this thread again.
The Milbank meter combo was a u5100-xl, or very similar. It is just a strange way that Milbank arranged the breaker bussing that allowed a two pole breaker to end up with both sides of it on the same feeding leg. (hope that makes sense) There was nothing modified or jumpered, but it would be easy not to notice if you just slapped the breaker in quick. I tried to find a cut sheet that shows the bussing but no luck.
http://www.milbankworks.com/specsheets/784572258785_SS.pdf if you look close you can see one of the breaker "stab" holes is empty in this very similar picture linked. I wonder if that is done to avoid the issue I ran into, maybe the one I worked on is older.
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oldsparky52
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- Wilmington, NC USA
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