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Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7246
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: 9 months ago.
Category: Electrical
Expert:  Mike G. replied 9 months ago.
Hi, I'm Mike G and I'll be assisting you. Is this a 3 phase or single phase service?
Customer: replied 9 months ago.
single phase
Expert:  Mike G. replied 9 months ago.
Turn off all breakers except the main. Retest both line and load sides of the main. Let me know the results.
Customer: replied 9 months ago.
I can't do that right now.
Expert:  Mike G. replied 9 months ago.
No problem. Do it when you can and then come back.
Customer: replied 9 months 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 9 months 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 9 months 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 9 months ago.
Could the problem be downstream of the panel?
Expert:  Mike G. replied 9 months ago.
Take the readings, give them to me and I can comment on the issue. Need to test not guess.
Customer: replied 9 months ago.
OK
Expert:  Mike G. replied 9 months ago.
I'll be here.
Customer: replied 9 months 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 9 months ago.
OK, is the service overhead or underground?
Customer: replied 9 months ago.
under ground
Expert:  Mike G. replied 9 months 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 9 months ago.
OK Thanks for your help.Gene
Expert:  Mike G. replied 9 months 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.

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