Flickering lights, squirrels, open neutral

This is about a household electrical problem I had.  The bottom line: if your lights flicker when your refrigerator comes on, call the power company.

The symptoms included (over the course of several weeks:)

  • flickering lights when the refrigerator came on
  • refrigerator PTC burned up
  • microwave sounding different; microwave LED panel dim; microwave diode failed open
  • cable modem died
  • computer and game console crashes

At first I thought the refrigerator was failing and putting too much load on its branch.  My computer was plugged into the same branch circuit (bad idea) and so it sometimes crashed when the fridge started.  I tried plugging the computer into a different branch circuit (an outlet on a different circuit breaker.)  That didn’t help.

I talked to my neighbours since they are on the same transformer on the street. But they were not experiencing problems.

I was about to start analyzing which leg of the 220V supply my refrigerator is on.  But I also called the power company, and they promptly came.

The lineman said a squirrel had chewed through the bare neutral leg of my drop.  The drop is the wires from the transformer on the street to your house.  Usually it is three wires, two insulated and one bare aluminum.  The neutral wire carries the weight, but also is a grounded part of the electrical path.

Squirrels and other rodents like to chew on aluminum foil.  Aluminum does rust or oxidize.  Aluminum oxide is another word for carborundum or sapphire.  After a layer forms, the layer protects from further corrosion (unlike iron oxide, which doesn’t protect from deeper corrosion, forming pits.)  I am wondering now whether rodents chew aluminum oxide because it is a salt, or rodents like bare aluminum.

When the neutral is open (chewed through), you still have power.  The end of the neutral at your house is also connected to a grounding rod at your house, forming a path to the earth back to the power company (to the nearest other grounding rod on the power companies’ equipment.)  But that path might be higher resistance than the neutral wire in your drop (if your grounding rod is corroded and the soil is dry?)  As the lineman explained it, when the neutral wire of the drop is open, when a largish load (a refrigerator is a large load when it starts, but not after it is running) comes on one leg (one 110V portion of the two in a center tapped 220V transformer, that the neutral wire taps the center of), the voltage on that leg (and all the branch circuits on that leg) temporarily drops, and the voltage on the other leg (and all the other branch circuits on it) increases.  This is a problem for electronics.

The chewed open I think was also intermittent.  The lineman said it was sparking.  When the wind blew, my symptoms were worse.  And it must have been progressive: the squirrel chewed until the original half inch wire was only a thread, then finally it was just two pointed wire ends in contact unless the wind blew.

The lineman said I could file a claim for damaged equipment.  This gets into politics.  Is a squirrel an act of dog?  Should society insure me?   If there is universal health insurance, should there be universal  squirrel-damage-to-electronics insurance?

The power company has tried to sell me insurance before.  It probably covers everything including squirrels.  I think they are emphasizing protection against lightning strike damage, which surely is an act  and which they probably don’t indemnify against otherwise.

Finally, I say we don’t need the squirrel insurance, but we do need to upgrade our electrical system.  The meter is smart and communicates with the power company for billing, it should be able to detect this problem and report it to the power company proactively.  Its mostly software which means it would cost almost nothing.




3 thoughts on “Flickering lights, squirrels, open neutral

  1. I am not so sure I understand the whole, “it’s mostly software which means it would cost almost nothing” –However I do agree the smart meters should (in theory) be capable of reporting high/low voltage on each leg. For some companies, they already monitor high/low voltage but only on the 240V for levels +/- 5 or 10% [depending on the company] which wouldn’t have any bearing on a bad neutral. Also, bad neutrals can happen on both overhead wires as well as underground wires and can also be caused by ants in a ground-mounted transformer. …Just some food for thought.

    • I am no expert on meters. But they have a microprocessor which has an ADC which converts analog voltage to a digital value. So if they are monitoring the 220V, they could add a few wires and switches, and also monitor the 110V on each leg, for the benefit of the customer. You’re right, it might not be ALL software (the extra wire and switch.) That might cost 10 cents more per meter.

      • I guess that would come down to the iconic “executive picking the right one out of a catalog” scene. Cost/benefit analysis plus considering the maintenance of the software feature set from the control room if/when a meter triggers an alarm – probably a bit more than 10 cents. (Granted the insurance here from the power company runs about $10/month and covers replacement value of damaged electronics.) Of course, you could blame building code for not requiring an interrupter installed in your breaker panel.

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