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Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7598
Experience:  Proven Professional 48 years Experience
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ComEd says transformer is OK. Electrician says: A phase to

Customer Question

ComEd says transformer is OK. Electrician says:
A phase to ground is 124 volts. B phase to ground is 125 volts. A phase to B phase is zero volts. What are the possible problems? Circuit breaker? ComEd is wrong? The line runs unmetered from the transformer to our distribution box supplying power for exterior lighting for our Homeowner's Association.
Submitted: 1 year ago.
Category: Electrical
Expert:  Mike G. replied 1 year ago.
Hi, I'm Mike G and I'll be assisting you. Is this a 3 phase or single phase service?
Customer: replied 1 year ago.
single phase
Expert:  Mike G. replied 1 year ago.
Turn off all breakers except the main. Retest both line and load sides of the main. Let me know the results.
Customer: replied 1 year ago.
I can't do that right now.
Expert:  Mike G. replied 1 year ago.
No problem. Do it when you can and then come back.
Customer: replied 1 year ago.
The electrician did that test. I think he said when the load was on one of the line voltage was zero. Something about a back load problem?
Expert:  Mike G. replied 1 year ago.
Knowing where the failure is should have presented the proper corrective action. Your electrician should have completed by making the required repair. Let me know the info asked for so I can diagnois the cause.
Customer: replied 1 year ago.
The electrician after checking the panel said that the problem was ComEd's. As I said ComEd came over and checked the transformer and said it was OK. Now I wonder about who to believe. The electrician then gave a $6500 estimate to replace the line not explaining his reason for the change in assessment.
Customer: replied 1 year ago.
Could the problem be downstream of the panel?
Expert:  Mike G. replied 1 year ago.
Take the readings, give them to me and I can comment on the issue. Need to test not guess.
Customer: replied 1 year ago.
OK
Expert:  Mike G. replied 1 year ago.
I'll be here.
Customer: replied 1 year ago.
Main "on" all subs "off". A is 126V. B is 0 V. A to B "0" off or on.BUT after many off/on cycles of the breaker now 126V between A and B. Breaker problem here? Still no 240 Volts no matter what I do. Also I get 114 volts on B with only sub #5
"on"...all other subs "off".
Expert:  Mike G. replied 1 year ago.
OK, is the service overhead or underground?
Customer: replied 1 year ago.
under ground
Expert:  Mike G. replied 1 year ago.
Well with the transformer checked by the tility and the reading indicating a failure before the main, you lost a leg on the underground. I suspect the service wasn't in conduit which is the probable reason for the failure.
Customer: replied 1 year ago.
OK Thanks for your help.Gene
Expert:  Mike G. replied 1 year ago.
You're welcome. There is one more possibility. If the utility didn't check the meter can connection, it could be there if you're lucky.