Ballancing on Voltage

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ARCORAZ

Member
This is a condo apartment, I was called because their lighting was getting 10% to 20% brighter when they Turing on Microwave or refrigerator is kicking in . I check in subpanel when all the circuit breakers are on. one incoming main line has 130 Volt and 2nd line 112 Volt. And when breakers are off both lines are balance on 121 Volt. I check All the neutrals are tight. And also I did try to run the microwave from different circuit, but it happened again.


I don't know what is it I am missing.
Anyone can help me
 
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GoldDigger

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ARCORAZ said:
I don't know what is it I am missing.
Anyone can help me
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The neutral wire from the subpanel back to the main may be tight where you are looking at it, but somewhere along the way back to the POCO transformer secondary center tap the neutral wire has a high resistance.
That is the only way that a measured phase to neutral voltage can be higher than the same phase to neutral voltage with no load.
 
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broadgage

Senior Member
Location
London, England
Agree, bad neutral.
If you are certain that you have not missed anything, then it must be upstream of where you checked.
Needs urgent investigation since a loose or poor connection is probably getting very hot and might start a fire, or fail entirely.
 
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ARCORAZ

Member
I just want to thank you all and let you know that the problem was lose neutral under main lug leaving from meter.
Thanks again
 
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