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Shazam! Off goes the microwave! But why?
January 25, 2011 8:10 AM   Subscribe

My power strip has been spontaneously switching itself to off when my microwave's going. Nothing's plugged into it but that microwave. What's going on? Is the microwave safe to use?

I have a Panasonic microwave oven, about 10 years old.

It's plugged into a power strip so that I can easily turn it off when not in use. It's the only thing plugged into that strip, and the strip is the only thing plugged into that outlet in my kitchen. I turn it on and off maybe four or five times a day for short-time things like tea and oatmeal.

Just in the past month or so, the microwave has switched off mid-use. I noticed that the button on the power strip is spontaneously resetting to "off". Earlier this week, it happened two times in a row, and I haven't used the microwave since.

What could be happening? Do you think the microwave is safe to use? I can easily swap in another power strip, but I really want to know what's going on and if I need to replace the microwave.

posted by cadge to Home & Garden (15 answers total) 1 user marked this as a favorite
Remember that the other name for "power strip" is "surge protector": i.e., there's a built in trip switch to protect your electronics from spikes in the power supply that might otherwise fry them. It's possible that there was a surge a month or so ago, and since then the strip has been trying to tell you it's time to move on. I would replace the power strip before replacing the microwave.
posted by xueexueg at 8:14 AM on January 25, 2011 [2 favorites]

Your power strip has a resettable fuse which the microwave is tripping. Plug the microwave directly into the wall outlet and see if the problem's solved.

If it is, you're just not using a hefty enough power strip. Microwaves pull a lot of amps, so you should either get a heavy-duty power strip, or skip the power strip altogether.
posted by odinsdream at 8:15 AM on January 25, 2011 [2 favorites]

Does your power strip have surge protection built in? I'm not an electrical expert, but I would assume that it matters in trying to figure out what's going on.
posted by Johnny Assay at 8:15 AM on January 25, 2011 [1 favorite]

The powerstrip is doing its job by tripping when the microwave draws more amperage than the powerstrip is rated for. It could well be that the microwave is failing.

Is there a reason you are putting the microwave on a powerstrip and not simply plugging it into the wall?
posted by Thorzdad at 8:21 AM on January 25, 2011 [1 favorite]

A friend of mine once asked me "Hey, guess what the first part to fail in CityCarShare cars is?". "I dunno," I said. "The rear view mirror".

You see, normal cars get wear and tear on things you'd expect. The breaks, the gas pedal, the shifter (if you have a manual car). But no car is designed to have the rear view mirror adjusted 20+ times a day.

As a non-electrician, I would say that probably your problem is the power strip, and not the microwave. They are probably not designed to be turned on and off 4 times a day for years. In response to "is this safe?" I would say "probably". What is your safety concern? Is it "am I microwaving my head?" I have no answer. Microwaves could be escaping your microwave oven, but I don't see how that would be related to an electrical fault. "Will my microwave start a fire?" Well, since you are in your home, I feel like this risk is small. Anyways, this is what circuit breakers are for.

It is possible that your power strip is acting like an advanced circuit breaker in this case. As a possible test, take unplug your microwave, plug in a hairdryer and run that for a few minutes. Of course now you're just left with the question "is my power strip inadequate, or breaking".

Finally (and sorry for venturing outside the scope of this question), your point raises another question for me. "Why do you want to turn off your microwave when it's not in use?" There are many valid reasons to do so, but if you are concerned about wasting electricity, I highly recommend purchasing a Kill A Watt to determine the value of unplugging this, or other, appliances. I found it super informative.
posted by Phredward at 8:28 AM on January 25, 2011 [1 favorite]

N'thing that microwaves use up a lot of juice and you're using a surge protector below its class.
posted by mkultra at 8:36 AM on January 25, 2011

Thanks for this input, everyone!

Yeah, my concern about the microwave was to avoid wasting electricity from the microwave hanging out in standby mode and running its clock.

I used to plug and unplug it directly into the outlet, but like Phredward mentioned, all that activity seemed like too much wear and tear on the outlet.

The power strip is old too, and I could replace it with one of the newer ones that's designed more for addressing standby/phantom power issues.

But will I just get the same problem of turning it on and off several times a day?
posted by cadge at 8:38 AM on January 25, 2011

Microwaves don't have a standby mode. They're either running or they aren't. The trickle of the LED clock is minimal. Certainly not worth plugging/unplugging the thing constantly.

Appliances that draw a lot of power, like microwaves, should be plugged directly into the wall.
posted by Thorzdad at 8:51 AM on January 25, 2011

Yeah, my concern about the microwave was to avoid wasting electricity from the microwave hanging out in standby mode and running its clock.

Honestly, this is crazy.
posted by empath at 8:52 AM on January 25, 2011

I'd also suggest using a Kill-A-Watt to ascertain exactly how much power that microwave is drawing in "standby" mode. It seems likely to me that you've already spent more on power strips [both out of your own pocket and in terms of what it cost to manufacture the thing] than the appliance consumes to run its clock [it's not like a TV, where standby mode keeps a bunch of components powered up for instant-on purposes] all year. That's just a guess, though, and the Kill-A-Watt will confirm or deny it.
posted by chazlarson at 9:04 AM on January 25, 2011

The energy cost of manufacturing and shipping a brand new power strip for you to go out and buy is high enough to run your microwave's clock for the rest of your life and then some.
posted by contraption at 9:13 AM on January 25, 2011

The switch in your power strip has in integrated circuit breaker that isn't designed for this kind of duty. IE: the switch is there more to reset the breaker than to act as a switch.

If it was me, considering only the microwave is plugged into the strip, I'd replace the wall outlet with a switched wall outlet. The linked switch is a GFCI which is a good idea if near a sink (required by code in Canada within 1.5 metres) however you can get them without GFCI for about half the price. You can also get them in t-Slots if the outlet you are replacing is a T-Slot.

Any actual switch products will handle that load as long as you aren't switching the outlet off when the microwave is running (many have a maximum inductive load of only a few hundred watts).
posted by Mitheral at 9:54 AM on January 25, 2011

The energy cost of manufacturing and shipping a brand new power strip for you to go out and buy is high enough to run your microwave's clock for the rest of your life and then some.

This. Just plug the microwave directly into the wall outlet and let the clock run.
posted by xedrik at 12:58 PM on January 25, 2011

I'll even do the math because I'm curious how this works out.

The illumination in the display is usually driven by LEDs that consume perhaps 100mW all told The clock and associated logic (waiting, with bated breath, for someone to finally press a button, etc) is driven by a microcontroller and real-time clock that together draw in the neighborhood of 50mW. (These estimates are both intentionally very high. 100mW of LED light is enough to build a decent-quality flashlight, for example.) Let's figure that all the power converters run at some abysmal number like 75% efficiency (note: switching power supplies operate in the high 90s). So that's a grand total of 200mW coming out of the wall.

Residential power goes for about 12 cents per kilowatt-hour in the US. 200 mW running all day long I'm going to round up to 5 watt-hours per day. 365 days of that is 1825 Watt-hours (that's 1.825 kWh), putting the YEARLY energy cost for running the clock and display at a figure we could round up to a quarter.
posted by range at 6:54 PM on January 25, 2011 [2 favorites]

I would just like to add, we've been unplugging our microwave when we leave the house because there were some local houses burned down by microwaves ... even when they weren't in use. (GE and Emerson were the guilty brands, I believe)

While this doesn't address your question directly, I just wanted to comment that I still think it's wise to cut power to the microwave when not in use ... even if there isn't any noticeable power savings, it still helps to prevent tragedies like these:

Microwaves linked to fires ... even when not in use!

posted by siclik at 2:17 PM on January 26, 2011

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