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While microwaving my dinner today, I measured the temperature of the outlet the microwave was plugged into. At the end of the 12-minute cook cycle, the hottest part of the outlet measured 160F. Is this a reasonable/safe temperature, or should I look into replacing the outlet? If I should replace it, should I replace it with a 15-amp outlet or a 20-amp outlet?

The outlet is a 15-amp outlet attached to a 20-amp breaker, and is about 40 years old (as is the rest of the wiring). The microwave draws, according to a Kill-A-Watt, exactly 15 amps.

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Older receptacles tend to lose their "grip" on the prongs of a plug. Many times this higher resistance connection creates a lot of heat. This is a VERY common problem with dryer receptacles for some reason.

I would definitely change the receptacle. Keep in mind, a 15A duplex receptacle is TWO 15A receptacles on a single device yoke. It is a 20A feed-thru device. So it is perfectly fine, safe and legal to use on a 20A circuit. A microwave would never be considered a continuous load so the 15A actual load is also fine, especially considering the 15A cord plug it has.

It is no problem to use a 20A receptacle, but there is NO benefit other than the prong configuration, unless of course you have appliances that have a 20A plug. In a home this is highly unlikely.

In high draw areas I like to suggest better quality spec-grade receptacles. They are made with stronger materials and have a much better grip on plugs. In my business I like to use them everywhere in fact. The couple of dollars difference is negligible in the long run.

My personal suggestion would be to change all the receptacles in the kitchen while you're at it and use GFI's at the beginning of the circuits for the countertop areas.

  • Do receptacles that don't see a lot of use, also lose their grip? I know this is a problem with receptacles where things are plugged/unplugged often, but is it also a problem where things are plugged in for a long time? – Tester101 Sep 14 '14 at 12:56
  • That I haven't noticed, but IMO anything from the 60-70's is pretty much junk and worth replacing. Residential materials from this era seem to be marginal at best. – Speedy Petey Sep 14 '14 at 13:01
  • I agree. I was just curious if you've seen receptacles wear out from just heat/age alone. – Tester101 Sep 14 '14 at 13:07
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    I would like to say that the higher quality 15A outlets generally have the same internals as 20A outlets, only the face piece is different. – Brad Gilbert Sep 14 '14 at 14:48

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