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Thread: Question about Air Conditioner motor surge protector

  1. #1

    Question about Air Conditioner motor surge protector


    Yesterday, our outside air conditioner compressor motor got knocked out because of a power problem, and we had to have a new one installed. This is what happened:

    At about noon, the electrical power went off for about two seconds, then immediately came back on before I had a chance to turn off the air conditioner thermostat. The compressor motor was running at the time of the power outage. When the power came back on, the compressor motor would not! Bottom line, we now have a new compressor motor (for about $400). No circuit breakers had been thrown, the motor simply died.

    I’ve talked to an electrical contractor about having a surge protector installed on the outside unit. He said that he could do it for about $125 and that by doing so, we could avoid such problems in the future.

    My question and concern is this:

    Since I’m not an electrician, I may be wrong about what I’m thinking, and that’s why I’m asking you pros. To me, a surge protector would protect the motor from a “surge” or “spike” of power, and I would assume that this means an amount of power MORE than normal. But would a surge protector have protected the motor in my case? Or was the motor knocked out simply because it hadn’t had enough time to recycle itself before attempting to come back on?

    In other words, does the power going out and immediately coming back on constitute a “surge”?

    Do any of you have such surge protectors on your A/C units?


  2. #2
    On all the air conditioning compressors I've ever dealt with, there was a thermal switch on the compressor. Many compressors will not start under pressure so if you turn the AC off and then turn it back on right away, the compressor will stall and not start up. Same thing will happen if the power goes out and then comes back on. [side note: most thermostats have a delay so if you turn the AC off and then turn it back on, the thermostat will not turn the AC back on for about 5 minutes.]

    Anyway, if the power goes out and then comes back on and the compressor stalls and overheats, the thermal switch will cut off the power to the compressor. Once the compressor cools off (and by then the pressure will be released), the thermal switch will cut back in and the compressor will run again.

    This overheating of the compressor is not a good thing, but it will not be a problem if it doesn't happen all the time.

    A "surge" would be a problem if lighting hits the power line, but when the power comes back on, it's no different than turning the unit on. The compressor has no power on it one instant and then the next instant it has full voltage on it.

    So if you want to protect against lighting, go ahead and put the surge protector on. But it won't do anything when the power goes off and then comes back on.

    Go into the world and do well. But more importantly, go into the world and do good.

  3. #3
    I agree with what Mike says to a point. In our rural area we suffer frequent power outages not necesarily from lightening strikes. Frequent causes are: wind blows down wires, cars hit poles, trees fall over wires, raccoons get in the transformer etc. Often times when these things happen there is a surge situation. A surge protector can protect from more than just lightening strikes.
    If it ain't broke...fix it anyways...that's why you told your wife you needed all those tools.

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