240 volt feed subpanel
#1
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240 volt feed subpanel
I'm feeding subpanel from main panel with aluminum direct buried cable. Each feed 120 volts with neutral cable. Worked for many years. Had a short to the circuit box and now volts drop to 60 V on one side and 180 v. on other line everytime I place a load on it. Any thoughts on what happened? Short was on minor 14 wire feed far from the circuit box.(20 amp circuits)
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Thank you. Could a #4 aluminum neutral wire have burned up with just a short in a small circuit 100's of feet away beyond a sub panel with breakers that didn't trip?
#4
Each feed 120 volts with neutral cable.
Short was on minor 14 wire feed far from the circuit box.(20 amp circuits)
What are the following voltage readings at the subpanel?
- Ground to 240 leg A.
- Ground to 240 leg B.
- Neutral to 240 leg A.
- Neutral to 240 leg B.
If both 240 volt legs are 120 volts to ground but both 240 volt legs measure ~0 to neutral then you have an open neutral as suggested by Wirenut.
Above assumes a code compliant 4 wire circuit with isolated neutral and bonded ground.
Could a #4 aluminum neutral wire have burned up with just a short in a small circuit 100's of feet
Last edited by ray2047; 05-03-13 at 09:22 AM. Reason: Correct voltage mistake.
#5
If both 240 volt legs are 240 volts to ground but both 240 volt legs measure ~0 to neutral then you have an open neutral as suggested by Wirenut.
Pesiatri, please give us the readings that Ray requested - each leg to neutral and each leg to ground. Since you say you observed this under load, please give us those readings twice - under load and without load. In addition, please measure the voltage across the two hot legs, also under load and without load.
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without a load and reset double breaker at feed panel, each line measures 120 v to neutral and ground. Once I place a load on, then it drops to 60 V on one side and 180 volts to other. Can I make feed line a 120 V system? not anything fed requires 240 volts now. Just feeding freezer in out building and maybe a table saw.The sub panel is 150 ft from main feeder panel.Thanks for all your help.
#7
Once I place a load on, then it drops to 60 V on one side and 180 volts to other.
#9
I have a 3 wire set up. Two hots and a neutral.
#10
without a load and reset double breaker at feed panel, each line measures 120 v to neutral and ground. Once I place a load on, then it drops to 60 V on one side and 180 volts to other. Can I make feed line a 120 V system? not anything fed requires 240 volts now.
What voltage did you measure between the two hot legs?
I would kill the power at the main panel and take everything to do with neutral in the subpanel apart and check for problems. One common one is that the feeder may have some strands either missing or deeply scored, if an insulated wire was pulled and had to be stripped to be terminated.
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thanks
thanks again, I had to go to work before I could try the extension cord readings. I'm working 7p-7a for the next 3 days and won't have a chance to check until mon. evening. If you could check back on tuesday, that would be very appreciated. Thanks again and have a good w/e.
#12
I got the impression that the Op wanted to re-purpose one of the hots to replace the failed neutral.
Last edited by pcboss; 05-05-13 at 02:19 PM.
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That is what I would like to do, if possible, because to bury new cable is a huge project in my situation. Can I get rid of failed neutral and use one leg as new neutral and the other hot for 120 service?
#14
What size conductors are feeding the panel? Electrically this could be done, however it could be a code violation. The size matters.
If this is changed, only every other breaker will be hot at the outbuilding.
If this is changed, only every other breaker will be hot at the outbuilding.
#15
Can I get rid of failed neutral and use one leg as new neutral and the other hot for 120 service?
Originally Posted by Nashkat1
I would kill the power at the main panel and take everything to do with neutral in the subpanel apart and check for problems. One common one is that the feeder may have some strands either missing or deeply scored, if an insulated wire was pulled and had to be stripped to be terminated.