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I live in a home that had a bad common lead connection, and this caused rotating blackouts throughout the house, and there were a couple of surge protectors that were overloaded - one blackened and produced a volume of smoke, in a room 15 feet from the load center.

After we had an electrician look at it, his determination was the problem was a bad common connection in the box out by the meter - the end of the cable was severely corroded, covered in green crust, and the insulation showed signs of burn damage as the cable had apparently overheated.

NOTE: I failed to state that he replaced the bus box and spliced a foot and a half of the common cable to fix that problem.

Now we have one side of the house that seems to trip the breaker on a regular basis, but it always resets and is fine until there are four or five lights or appliances (a combination of three or four rooms) on simultaneously. Shouldn't you be able to have every light in the house on and not trip off a breaker, effectively shutting down that side of the house?

This has not happened before the bad common incident, since then, it is always the same breaker that trips. Only one breaker and it never did this in the five years we've lived here before that problem. I think this is telling me two things, one - that the breaker may have been weakened by the drop-outs and surges during the bad common problem, and the wiring in this house is not correct for code. My biggest concern isn't the breaker itself, but I am wondering if this is dangerous. Am I going to wake up some night to find the place on fire? Can I just replace that one breaker and be OK, or will I have to get an electrician to rewire the house? I am really worried this will be beyond my means to repair. Help!

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    If the problem is at the meter then call your supply company and have come and them fix it. Feb 3 '17 at 11:38
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    If you don't get that neutral fixed, you surely could wake up on fire. Get the neutral fixed first, then evaluate the problem with the breaker. My guess is that the breaker will operate normally, once the other problem is handled.
    – Tester101
    Feb 3 '17 at 11:38
  • I forgot to mention that the common was repaired the Monday following the Friday night that the blackouts occurred. Before I could stop it the furnace control transformer fried and we had no heat that week until I could get a replacement. Now all we have is this breaker trip problem that didn't happen before the bad common. Could spiking voltage damage a CB in a way that it would trip before the nominal draw was reached? Its always the same CB, at night when lights are on and appliances are used in the kitchen. Is the wiring wrong all the one side of the house runs on one breaker?
    – SFC
    Feb 4 '17 at 18:21
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CALL YOUR ELECTRIC UTILITY NOW ON THEIR EMERGENCY NUMBER

You have a bona fide electrical emergency right now due to that failing neutral, and since it's in the meter pan, it's the utility's job to fix. Call them up on their emergency number (same number that you'd use to report a power outage) and tell them that the neutral in your meter pan is failing as well as giving your address. Until then, keep loads to an absolute bare minimum as the voltage at your outlets is going to be all over the map.

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  • We had the common replaced and the bus box as well the two days after the rotating blackouts began, over this past Halloween weekend. This breaker tripping situation has been going on for a few weeks and it has me wondering if the bad common (now corrected) could have damaged the breakers in a way that makes them trip at a lower level than they are normally designed for.
    – SFC
    Feb 4 '17 at 18:07
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The bad common incident isn't over! You need help NOW!

The symptoms you are reporting now are the same as for a lost neutral. So it isn't fixed.

A lost neutral will destroy most of your appliances and burn your house down. Yes it will, no exaggeration.

Call the power company on the emergency number

The problem is in their meter pan, and they need to fix it. Use the power outage number because this actually is a power outage. Oh, speaking of that---

Turn your main breakers off NOW

Avert further damage by turning your main breakers off right now. Yes, the cold and dark sucks, but the power company should be enroute.

Your dryer and oven/stove may give fatal shocks right now

Many houses still use an old, 3-prong "NEMA 10" connector for electric oven, range and dryer. Under certain conditions it can electrify the metal parts of the machine. This is one of those conditions. This is not an issue for the 4-prong NEMA-14 sockets. Even if you ignore all my other advice, shut off the breakers for dryer and oven/range.

Here's what's happening

Here's how house wiring is normally done.

enter image description here

Notice how it's 2 complete 120V systems stacked, with a neutral being used as a shared common, to save the expense of double wires. Notice this system is imbalanced already, with 3 light bulbs and the dryer load on the upper. This imbalance is normal. What happens if neutral disconnects at the transformer? Big trouble. Without neutral to force them to 120V, one will be over 120V and the other will be under 120V. They will still total 240V, so the water heater (which isn't connected to neutral) won't care.

The ones which are over 120V, however, will tend to burn out, blow up or catch fire. When that load is destroyed, it will imbalance things even more, stressing the next load, blowing that up, etc. etc. Bad news. If you're lucky enough to have a circuit breaker trip, it's because a load is malfunctioning so badly that it drew massive current.

If you really need to turn something on

Being winter, I wouldn't be surprised if you'd really like to run the furnace.

First, you don't dare turn on anything that is 120/240. That means it has a double breaker, and it also has a neutral wire (like the dryer in the above diagram). Aside from potentially burning out the 120V part of it, you could have that NEMA 10 hazard I mentioned above.

Now - this requires some pro knowledge - if you have loads which are 240V-only and do not use neutral at all (like the heater in the above diagram), you should be able to turn those on.

Other than that, you can't. Why? Because ground connects to neutral actually on your side of this break. If neutral is broken, the current will seek to return through ground. Dirt isn't a very good conductor, so that will be quite weak (and that's why some appliances are barely working). Ground not being a satisfactory current return, it will also push through other potential paths -- such as you or your family members.

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  • We had the common replaced and the bus box as well the two days after the rotating blackouts began, over this past Halloween weekend. This breaker tripping situation has been going on for a few weeks and it has me wondering if the bad common (now corrected) could have damaged the breakers in a way that makes them trip at a lower level than they are normally designed for.
    – SFC
    Feb 4 '17 at 18:04
  • Occam's Razor says the likeliest theory is the simplest. Without a neutral wire, a breaker has no ability to even know what voltage is going through it. However, followup problems with recent work are perfectly common. The decider would be checking with a voltmeter, or plug-in power monitor such as a Kill-a-Watt. Each 120V leg should be within 5V of the other, and almost exactly half 240V voltage. If you turn on a big 120V load like a George Foreman or hair dryer on a different circuit, it should move less than a volt. Feb 4 '17 at 18:47
  • Thanks, I will use that information to get it checked out.
    – SFC
    Feb 6 '17 at 1:04

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