Is my house about to burn down if I use my new microwave?

About a month ago, I bought a new microwave. However, the guy who installed it noticed something strange; the old microwave had the plug at the end of its cord removed, and attached to another cord inside an electrical box in my cabinets, with the other cord attached to the same outlet as my refrigerator, while an outlet directly above the microwave was left unused, so he plugged the new microwave into the unused outlet and left.

It never occurred to either of us that the two outlets were connected to two different lines; the one the microwave was using was connected to a 20A breaker, and has only that outlet connected to it, while the one he plugged the microwave into was on a 15A breaker that also included all of the kitchen and living room lights plus the TV, DVR, and stereo. This is Not A Good Thing when the microwave by itself draws 14.75A of current when it is running.

I called in an electrician, and he did something similar to the old setup (the only difference is, rather than remove the plug from the microwave's cord, he installed an outlet into the electrical box and plugged the cord into that). However, he noticed that the outlet that the microwave and refrigerator are plugged into is not a 20A outlet, but a 15A outlet (the jacks are missing the "T-tab"), even though the breaker is marked 20A, so I assume it has AWG 12 wiring.

Am I about to burn my house down by having what appears to be a 15A outlet hooked up to what had better be a 20A if the microwave and refrigerator are running at the same time?

***Disclaimer*** I'm a DIY'er that takes as many chances as I can fit into a day.

It's not "good". I'm not terribly good with electric, so can't tell you how much that 14.75 will drift, or for how long. But since it's a 20a breaker, it will allow an overrun through that outlet, which will heat it up. That's bad cuz heat is one third of fire, and the other two thirds are right there.

The good is that 15a is the safe range it's been designed at, meaning it CAN LIKELY handle 50-100% over that. This is a gambling board, right? =) Also, it's a microwave, so I would hope you are a decent, self-respecting human that uses it minimally. I dunno what people use these things for, but I'm guessing we're in the sub-2min range, which isn't terribly alarming, either.

Part of me says wing it. The outlet is right there (I assume), and you'll never be gone long, so if the Big IF happens, you should be able to easily tell if there's an issue well before you create a conflagration. If however you're one of those hedging fellows, then swapping outlets is about as elementary as a home repair can be. Talking 15min for a complete novice. AS LONG AS YOU CUT THE POWER WHILE REPLACING, you really can't mess it up. Worst case is it doesn't work / trips breaker, in which case you just flipped the two wires inside. Flip 'em back and it's good to go.

You MUST cut the power, though. I flip both the outlet breaker as well as the 110v to the entire house, as I hate being electrocuted that much. It absolutely can kill you, so do that first, check it thrice, lock it out, and do it when no one's home, if able. But other than that VERY IMPORTANT step, it's perfectly simple to replace yourself.

ETA: Unless your house is very old. 50+yr insulation (talking the rubber on the electrical wires) is completely cured at that point and has the consistency of a month old graham cracker. Manipulating it at all will crumble it and leave exposed wires, giving you a "constant trip" situation in the breaker box.

2nd edit: I think petroglyph was a lineman. If he's not here to cuss me out shortly, I bet he has a perfect answer.

Quote: Face

***Disclaimer*** I'm a DIY'er that takes as many chances as I can fit into a day.n

As with just about anything, the internet's your friend. https://www.thisoldhouse.com/how-to/10-wiring-problems-solved

Have you ever noticed how mechanics run the worst cars, and carpenters leave a few nails out, and probably programmers are a few ap's short of a load? That's because they know they can fix whatever it is in a jiffy.

I prefer working on voltages starting at 2400 and above, but will stoop to fix a receptacle, if it looks like it is about to catch fire. He hired a pro to put in the plug, right? No biggy. That's the great thing about electricity, after you've twisted a few wires together, what else can there be?

I will say, I thoroughly dislike those 'stab' in connections on the back of cheap receptacles. They have caused more than a few problems. At least go through the trouble to make a C out of the end of the wire and put it underneath the screw, and tighten.

All this is beyond me. Refrigerators draw a lot of current when they start up.

Microwaves draw peanuts for the clock and only slightly larger peanuts when operating.

Transient loads usually do not matter much.

Quote: ThatDonGuy

I called in an electrician, and he did something similar to the old setup (the only difference is, rather than remove the plug from the microwave's cord, he installed an outlet into the electrical box and plugged the cord into that). However, he noticed that the outlet that the microwave and refrigerator are plugged into is not a 20A outlet, but a 15A outlet (the jacks are missing the "T-tab"), even though the breaker is marked 20A, so I assume it has AWG 12 wiring.

You mean the outlet is like the one on the left instead of the right?




That's fine.

15A outlets can be installed on 20A circuits (but not vice versa). It's likely a 20A circuit if the breaker is rated for that.

As long as the appliance doesn't have a prong turned 90* to fit that 'T-Slot' it's fine to run on either a 15A or 20A circuit. If the microwave and refrigerator are on the same 15A circuit and draw more than 15A all that will happen is the breaker will trip.

DISCLAIMER THAT I'M NOT AN ELECTRICIAN

The silver lining is, if your house burns down you'll have a good story about how you got your advice on a gambling site.

Quote: ThatDonGuy

... the guy who installed it noticed something strange; the old microwave had the plug at the end of its cord removed, and attached to another cord inside an electrical box in my cabinets, ....

I would consider this a little more than "strange." I think that in most localities it would be a housing electrical code violation. Not an electrician myself, but it is my understanding that codes require that microwave ovens (freestanding or built-in) be plug-in appliances rather than direct-wired and that there be convenient access to the plug and outlet.

My own microwave is a combination unit that includes the microwave oven plus the air filter/fan and lighting over my stove. It lists as 120v & 1800 watts, which does indeed suggest 15 amps total. The owner's manual says it requires a 15- or 20-amp electrical supply with a fuse or circuit breaker. It recommends (1) a time-delay fuse or breaker and (2) a separate circuit serving only this appliance.

In my case, I have a 15-amp outlet with the second receptacle on that outlet also serving two under-cabinet 15-watt (1/8 amp) fluorescent light fixtures. Yes, 15 + 1/8 + 1/8 > 15, but I have never had any problem with this setup. On the other hand, I don't know that I would feel comfortable using a 15-amp microwave together with a refrigerator on a 15-amp outlet.

Since ThatDonGuy's original setup may have violated electrical codes, I wouldn't automatically assume that a 20-amp breaker necessarily means that it is connected to a circuit that will handle 20 amps. If you are considering replacing the outlet, you should be able to check out the wiring itself and get an idea of the gauge.

Not sure that I completely understand the configuration of the outlets. Is it possible that outlet connected to the dedicated 20-amp breaker was intended for the microwave oven and that the refrigerator was supposed to be plugged into the 15-amp outlet?

Replacing an outlet is a 10 minute job. A 20a outlet costs about $5. I'm with petroglyph - don't use a quick-connect setup. Under the copper flap or around the screw (depending on brand) is much better.

Quote: rxwine

The silver lining is, if your house burns down you'll have a good story about how you got your advice on a gambling site.

LMAO! :D

Quote: rdw4potus

Replacing an outlet is a 10 minute job. A 20a outlet costs about $5. I'm with petroglyph - don't use a quick-connect setup. Under the copper flap or around the screw (depending on brand) is much better.

You should NOT replace a 15A outlet with a 20A outlet unless you KNOW you have 12ga wire all the way back to the circuit box, and also need to have a 20A breaker.

Why must a microwave be installed?

Quote: Dalex64

You should NOT replace a 15A outlet with a 20A outlet unless you KNOW you have 12ga wire all the way back to the circuit box, and also need to have a 20A breaker.

You could install a 30A outlet in the same place, just better contacts. The difference is how much load you expect to connect. Don't change the breaker size up.

Quote: onenickelmiracle

Why must a microwave be installed?

Manny houses and condos come with one that's installed under the cabinets over the stove with a fan unit. Should be easy enough to do yourself but I haven't really looked at how they have it attached and whatnot.

Wtf, all of a sudden everyone’s a damn electrician around here. All I know is after my brother shoved a key into an outlet when he was like 4, he figured out those things are bad news bears...And I’ve probably almost electrocuted myself plenty of times working on fixing those things. They scare the s*** outta me, too....even changing the bats on my vape I flinch every now n then.

Quote: RS

Wtf, all of a sudden everyone’s a damn electrician around here. All I know is after my brother shoved a key into an outlet when he was like 4, he figured out those things are bad news bears...And I’ve probably almost electrocuted myself plenty of times working on fixing those things. They scare the s*** outta me, too....even changing the bats on my vape I flinch every now n then.

I am also like your brother when I had to learn the hard way that you should never microwave Burger King aluminum foil wrapped Whoppers. Put it in for like THREE seconds, and pop, pop, pop, it looked like an electrical explosion. Pretty scary. I learned to never do that again and BK stopped wrapping food in aluminum foil presumably after many people did the same thing.

Quote: AxelWolf

Manny houses and condos come with one that's installed under the cabinets over the stove with a fan unit. Should be easy enough to do yourself but I haven't really looked at how they have it attached and whatnot.

Exactly - mine is an over-the-range unit with a fan.

Quote: ThatDonGuy

Exactly - mine is an over-the-range unit with a fan.

Same as mine, which I tried to describe above.

Quote: onenickelmiracle

Why must a microwave be installed?

In addition to the multi-function units (with lights and fans and such), many microwave ovens are designed to be installed within the kitchen cabinets, like a built-in wall oven. Mostly, it is an issue of appearance.

Quote: RS

Wtf, all of a sudden everyone’s a damn electrician around here. All I know is after my brother shoved a key into an outlet when he was like 4, he figured out those things are bad news bears...And I’ve probably almost electrocuted myself plenty of times working on fixing those things. They scare the s*** outta me, too....even changing the bats on my vape I flinch every now n then.

Yeah, I know right? It's hard to swing a dead cat without hitting one of them.

Quote: petroglyph

You could install a 30A outlet in the same place, just better contacts. The difference is how much load you expect to connect. Don't change the breaker size up.

An appliance with a 20A or 30A plug on it has the potential to draw 20A or 30A.

There is a reason that they put one of those plugs on instead of a 15A plug.

If you hook that up to a 15A breaker, with a 20A+ appliance using all of the power that it might, then it will blow a lot.

If you replace the breaker but only have 14GA wire, then the wire can get hot and that IS a fire hazard.

If you just want it for "better contacts" in the outlet, then you are misleading a future homeowner as to the capacity to the outlet, and yourself if you forget later. That is dangerous.

Quote: Dalex64

If you just want it for "better contacts" in the outlet, then you are misleading a future homeowner as to the capacity to the outlet, and yourself if you forget later. That is dangerous.

Right. 20A and 15A outlets are identical except for the T-Slot - the 15A 'rating' refers to the plug configuration rather that what the contacts can actually handle.

If you look carefully at a 15A outlet it will say that it's rated for 20A passthrough.

Quote: Dalex64

An appliance with a 20A or 30A plug on it has the potential to draw 20A or 30A.

There is a reason that they put one of those plugs on instead of a 15A plug.

If you hook that up to a 15A breaker, with a 20A+ appliance using all of the power that it might, then it will blow a lot.

If you replace the breaker but only have 14GA wire, then the wire can get hot and that IS a fire hazard.

If you just want it for "better contacts" in the outlet, then you are misleading a future homeowner as to the capacity to the outlet, and yourself if you forget later. That is dangerous.

That is why I usually don't discuss electricity with people, anybody that has twisted two ends together thinks themselves an expert.

For the safety of everyone involved it would probably be best to close this thread. I see several misnomers already.

Quote: ThatDonGuy

Exactly - mine is an over-the-range unit with a fan.

My fan seems to go on and off by itself whenever it scenes too much heat or whatever. I have never had a microwave go out, so I never really thought what one would do with a built-in microwave once it went out.

p.s. You haven't lived unless you have stuck your finger in light bulb socket, put a butter knife in the toaster, got shocked and knocked on your ass by a soda machine, or pissed on an electric cow fence(or tricked some other kid into touching one).

Quote: petroglyph

That is why I usually don't discuss electricity with people, anybody that has twisted two ends together thinks themselves an expert.

For the safety of everyone involved it would probably be best to close this thread. I see several misnomers already.

Changed your mind from "you win" eh?

Feel free to take my post to a licensed electrician of your choosing.

Quote: AxelWolf

My fan seems to go on and off by itself whenever it scenes too much heat or whatever. I have never had a microwave go out, so I never really thought what one would do with a built-in microwave once it went out.

p.s. You haven't lived unless you have stuck your finger in light bulb socket, put a butter knife in the toaster, got shocked and knocked on your ass by a soda machine, or pissed on an electric cow fence(or tricked some other kid into touching one).

LOL made me laugh, I tricked many a kid into touching the electric fence and saw a few guys do a dance after pissing in the bushes not knowing the fence was there.

Quote: Dalex64

Changed your mind from "you win" eh?

Feel free to take my post to a licensed electrician of your choosing.

I almost always like your posts, you are obviously very intelligent and write well. I've been in the electrical field since 71. I've worked with dozens and dozens of licensed electricians.

I removed "you win" which I wrote, because of visiting similar discussions for decades. I know how it ends. I was also the trouble shooter for different power company's. I don't want to argue about it, regardless of whether or not i am right, there is no way to win. The simplest discussion about whether or not a .69 receptacle is the same quality as a 12.00 Lufkin, invokes an argument. Whether or not silver has the same conductivity as copper or aluminum is lost on people that haven't done it for a living, or why contact surface area is important for safety factor. Or whether or not fuses are safer than breakers.

There are more people killed from 115 volts than any other voltage. [useless factoid] But repeating it enough keeps some people from making toast while taking a bath. There are things that aren't taught, that are still true.

Quote: AxelWolf

My fan seems to go on and off by itself whenever it scenes too much heat or whatever. I have never had a microwave go out, so I never really thought what one would do with a built-in microwave once it went out.

p.s. You haven't lived unless you have stuck your finger in light bulb socket, put a butter knife in the toaster, got shocked and knocked on your ass by a soda machine, or pissed on an electric cow fence(or tricked some other kid into touching one).

What!? Care to explain (the bolded)...?