I shut off the power to this entire house, from inside, the larger main switch at the top of the panel. 12 hours later we started hearing the garage door opener circuit board make a noise like a relay flickering. Seems it's toast upon inspection (ordered part for $60).

Would a small surge protector like the one below prevent that from happening again to another $200, 10 year old device like that?


Backstory: We bought this home and have found some weird stuff I've yet to dig into. 50-90vac on some of the switch plate screws. Other places, 30vac still when the circuit breaker is off. Other outlets have only 30vac hot to neutral. All on one line luckily. But that's another question for another time. I will check all that out later this month.

  • The opener fried when the power was off, or when you turned it back on?
    – Tester101
    Commented Mar 24, 2016 at 22:38
  • You're measuring 50-90 volts between the switch plate screws and what?
    – Tester101
    Commented Mar 24, 2016 at 22:40
  • When power turned back on. Would be interesting to know if cutting power... well, I guess if it was in motion? Hmmm. And to answer the other question, to ground. Lots of issues. No ground found on some outlets. Etc.
    – Mr P.
    Commented Mar 25, 2016 at 6:57
  • A known good ground, or something you think is grounded?
    – Tester101
    Commented Mar 25, 2016 at 11:08

2 Answers 2


The most common surge arrestors are MOV (metal oxide varistors). The one you linked will protect a single circuit but the power issues need to be fixed first or it may fry the unit (more than a 600 joule spike and the let the magic smoke out). They work by dumping spikes to ground but they are limited in the power they can dissipate. They also make larger units that can be installed to protect the entire house. breaker style I put a larger one in that required a external box and a 20a 220 breaker to feed it after that I quit having equipment not on UPS's fail. (we did have very noisy power in that house because of the industrial loads down the street).

  • I've got a large surge suppressor as part of my solar installation. It's on the other side of a secondary wattmeter, but it's probably giving me some protection.
    – keshlam
    Commented Mar 24, 2016 at 22:12

No, a surge protector will not protect you from normal switching. It won't do any harm, though, and it will protect you from larger surges.

Electronics does fail most frequently when being turned on or off. That's just the nature of the beast. It was ready to die; it died; it happened to die when you were playing with the breaker rather than when the power company had a hiccup. It Happens.

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