Power out to half the house...with a twist

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  #1  
Old 05-15-13, 04:48 AM
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Power out to half the house...with a twist

Power went out to the lights and receptacles on the back half of our first and second floor yesterday. I checked the breaker panel and appear to have power to the load side of all circuits. One AFCI breaker doesn't trip when I press test, so I replaced that, but no change. While waiting for the electrician to arrive (hopefully tomorrow) my son turned the oven on, and all of our power was restored. About fifteen minutes after the oven turned off, our power went out to the back half again. The house is about 9 years old, has 150 amp service, main breaker outside at the meter, subpanel in basement. Oh, about two years ago, we turned our old range on and blew the main breaker. I replaced that range and have not had any problems til now.
 
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Old 05-15-13, 04:51 AM
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Welcome to the forums! Do not delay. Call the emergency number to your local Power Company, now. It is possible there is a problem on their end of the lines. It is a free, required service, and you may not need an electrician. Keep us posted. Call them, now, please.
 
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Old 05-15-13, 07:10 AM
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I agree, if it is a loose or broken nutral on the power comapanys side it can fry anything in the house that's plugged in.
I'd kill the main breaker until they come to check it out.
I've seen more then one house burn down from this.
 
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Old 05-15-13, 02:14 PM
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Since you only lost power on some circuits and not on others, the problem is not with the supply (power company) neutral. You may have one or more open neutrals inside your system.

I checked the breaker panel and appear to have power to the load side of all circuits.
Do you mean that you used a multimeter to check for voltage between the connecting terminal and neutral on each breaker, and that you found ~120V in each case? If so, did you also test for 240V across the two terminals of any 240V breakers?

Did you find more than 120V hot-to-neutral anywhere? That's a sure sign of an open neutral.

While waiting for the electrician to arrive (hopefully tomorrow) my son turned the oven on, and all of our power was restored. About fifteen minutes after the oven turned off, our power went out to the back half again.
It sounds like you have a loose connection on some or all of one of the two legs of your 120/240V service.

Since you have an exterior disconnect, you could turn the power off there and check all of the connections inside your distribution panel for tightness. Don't over-tighten them.

Since your distribution panel is a subpanel, you can also visually inspect it to insure that the grounds are separate from the neutrals, that the grounds are bonded to the box and to earth, and that the neutrals are isolated from earth bond. In most panels, up to two ground wires of the same size may be terminated under one screw but each neutral must be individually terminated.

There's probably not a lot more that you, as a homeowner, can do before your electrician arrives.
 
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Old 05-15-13, 05:54 PM
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Did the oven succeed in cooking anything when it was switched on
 
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Old 05-15-13, 06:04 PM
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Did the oven succeed in cooking anything when it was switched on?

When your son turned the oven on, current was able to flow through the oven elements to get to the other (dead) leg of the electrical system and energize lights, etc. But only a small number of watts could be drawn before the voltage for the lights would drop (the lights would dim) and the oven would heat up a little.
 
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Old 05-15-13, 07:00 PM
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I sent the OP a PM, but no response, yet. Maybe he will happen by and trip on the questions.
 
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Old 05-18-13, 08:20 AM
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I got a response via PM from the OP. Seems all is well, although a little scary:

"We are, we had the power company out, and an electrician at the same time. Turned out the lead from the meter mount to our main breaker had burned through, and left an open. That was why we had power in half the house. It also explains why turning the stove on led to a back feed and restored power to the other leg. All is good now though, just kind of amazed, seeing a 3/0 lead burned through. It also explains the flickering lights for the past couple weeks. Thanks for your help."
 
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Old 05-18-13, 02:57 PM
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Thanks for the follow-up, Chandler. An open hot, though, poses no hazard. That's what we do every time we flip a snap switch "off."
 
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