Hot to ground 50v neutral to ground 50volts hot to neutral 120volts please help ideas

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We did an electrical sub panel change from an old 6 space pushmatic to a new 6 space square D. When we were turning the breakers back on one of the single pole breakers tripped immediately. The really really old microwave quit working and smelled like burning wires, then we realized that the fan motor to the the refrigerator also burned out which was plugged into the same circuit as the microwave. The receptacle shows open ground at the receptacle but it has a grounding conductor connected. Receptacle shows 60volts from hot to ground and 55volts from neutral to ground but 116 volts from hot to neutral. Also the ice maker on a different circuit fed from the same sub panel appears to have burned up. We replaced a 6 space sub panel with new 6 space sub panel and put it back together exactly the way the existing was installed and now we have a couple smoked old appliances. I don't think it is the electricians fault can somebody please help? Thanks
 

GoldDigger

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Since voltage hot to ground and hot to neutral are not the same, the neutral and ground must not be connected. The most common cause of this is an open neutral. The POCO neutral should be grounded at the transformer.
An open neutral can put up to 240 volts across some loads. There are threads here which describe the effects in detail.

Things you could have done to cause this include miswiring and breaking a marginal neutral wire while handling it.
Is the service 120-0-120 single phase?
If the neutral was already broken, you could have made a small problem much worse by not bonding the ground to neutral in the sub. The old sub may have incorrectly but protectively have had the bond installed.
The liability in that case is less clear, but the electrician did not make simple but not necessarily routine tests before energizing the panel.
 
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Johnnybob

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Location
Colville, WA
Since voltage hot to ground and hot to neutral are not the same, the neutral and ground must not be connected. The most common cause of this is an open neutral. The POCO neutral should be grounded at the transformer.
An open neutral can put up to 240 volts across some loads. There are threads here which describe the effects in detail.

Things you could have done to cause this include miswiring and breaking a marginal neutral wire while handling it.
Is the service 120-0-120 single phase?



I was just gonna say, we did a tree job when I was a youngster (in Pollock Pines, actually) where the foreman dropped a large white oak limb across the service drop, parting the grounded conductor in the triplex. We didn't notice it, of course, and when the home owners came home, all their 120v appliances had leaked all the smoke out! You know how hard it is to capture all that smoke and get it all stuffed back in. So all those appliances that were suppose to see 120v were now seeing 240! Yup, we were all looking for new jobs by the end of the week.
 

rlundsrud

Senior Member
Location
chicago, il, USA
Since voltage hot to ground and hot to neutral are not the same, the neutral and ground must not be connected. The most common cause of this is an open neutral. The POCO neutral should be grounded at the transformer.
An open neutral can put up to 240 volts across some loads. There are threads here which describe the effects in detail.

Things you could have done to cause this include miswiring and breaking a marginal neutral wire while handling it.
Is the service 120-0-120 single phase?
If the neutral was already broken, you could have made a small problem much worse by not bonding the ground to neutral in the sub. The old sub may have incorrectly but protectively have had the bond installed.
The liability in that case is less clear, but the electrician did not make simple but not necessarily routine tests before energizing the panel.


Why would you say the neutral should be bonded to the ground in the sub panel? The neutral should be isolated from the ground in the sub panel. There also needs to be a separate ground bar in it for landing the ground wires for the branch circuits.

I do agree that it is almost certainly an open neutral that has caused this issue. I also believe that this was caused by the OP, either with incorrect wiring or by inadvertently breaking a neutral connection somewhere. It's probably not what the OP wants to hear, but it happened as a result of the work they did.
 

growler

Senior Member
Location
Atlanta,GA
We did an electrical sub panel change from an old 6 space pushmatic to a new 6 space square D.


What kind of feeder was going to this sub panel and how far to the main panel? Any junction boxes?

Just because it was the electrician's fault doesn't mean you can't talk your way out of it. People get away with murder by getting a good lawyer.
 

GoldDigger

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Why would you say the neutral should be bonded to the ground in the sub panel? The neutral should be isolated from the ground in the sub panel. There also needs to be a separate ground bar in it for landing the ground wires for the branch circuits.

I do agree that it is almost certainly an open neutral that has caused this issue. I also believe that this was caused by the OP, either with incorrect wiring or by inadvertently breaking a neutral connection somewhere. It's probably not what the OP wants to hear, but it happened as a result of the work they did.

Nowhere did I say that the neutral should be bonded to ground in the sub panel. I intended to take note of the fact that IF there had been a bond in the old panel it would have limited the voltage shift from the broken neutral to the point where it might not have been noticed. Then the correct wiring of the new panel by the OP's electrician would have caused the voltage shift to become much bigger.
 

Dennis Alwon

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Chapel Hill, NC
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I agree that somewhere someone lifted a neutral and burned up some of the appliances. When you lift the neutral when the circuit is energized you are putting 240V into some of the circuits.
 

rlundsrud

Senior Member
Location
chicago, il, USA
Nowhere did I say that the neutral should be bonded to ground in the sub panel. I intended to take note of the fact that IF there had been a bond in the old panel it would have limited the voltage shift from the broken neutral to the point where it might not have been noticed. Then the correct wiring of the new panel by the OP's electrician would have caused the voltage shift to become much bigger.

I get it now, I was suprised and confused when I read your initial post. Thank you for the clarification.
 

GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
I get it now, I was suprised and confused when I read your initial post. Thank you for the clarification.
One more observation:
If this had been the service panel with a bad service neutral the high electrode to earth resistance would allow a substantial neutral shift.
But if only the feeder neutral was bad an extra bond would have put the.neutrsl current on the low resistance EGC and the neutral shift would be no more than with an intact neutral.
 
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