Microwave Oven

I am replacing an above-the-range microwave oven. The current electric wire going to the microwave is a 14/2 line that is shared with a couple of other light fixtures. The type of microwave that I bought requires a 110 line but dedicated. I am curious if what is already installed is enough for the new microwave. Thanks for the help!

 

You say that the new unit calls for a "Dedicated" line and that the existing line also serves some lighting. The word dedicated means exactly that, nothing else on the line. Your microwave should have it's own dedicated line.

As for the size, in kitchens the code requires that we use 12 guage wire which is rated for 20 amps. The wire that you say is existing is number 14 and is only good for 15 amps. Keep in mind that you have load on that 14 already with the lights.

Play it safe!!! Run a new dedicated line for the microwave and rest easy at night knowing that you did the right thing.

 

A built-in appliance can be on a 15 amp circuit. Only the countertop receptacles must be 20-amp.

Read the electrical specs on the sticker inside the microwave. Tell us what it says. Then tell us the wattage of the lighting on this circuit.

 

Thanks for the replies so far. Here is the rating info about the it: 120volts AC, 60 Hz, 15 Amps, and 1.58 kilowatts. The only light on that same circuit are a breakfast nook light and a pantry light that are on the other side of the room. Instructions also say, "the power supply cord and plug should be brought to a separate 15 or 20 ampere branch ciruit single grounded outlet." I hope this helps.

 

You'd be pushing your luck if you install this microwave on this circuit. I'd recommend a new circuit. But you can try installing it here if you want. You might need to make sure the other lights are off when you run the microwave, depending on their wattage (which you didn't say). If the breaker trips even once, add a new circuit.

 

I gotcha so far. What if I took one of the lines going to the disposal or dishwasher (make those two appliances on one line) so I can use a separate circuit just for the Microwave? I read in some of the books that you may put combine the disposal and dishwasher on the same circuit.

 

The dishwasher and garbage disposal are not required to be on a seperate circuit unless the two loads are over the circuit capacity. Look on the name plates and check the current/power draw. It usually is not a problem because many dishwasher instructions tell you not to operate the garbage disposal while the dishwasher is operating.

 

Usually when a dishwasher and disposal are on the same circuit, it's a 20-amp circuit. You didn't say whether that circuit is 15 or 20 amps.

 

both the dishwasher and the disposal are on their own 15amp circuit.

 

The NEC states that if a fastened in place appliance uses more than 50% of the branch amperage then the branch must be "dedicated" with nothing else.

NEC also states that you must follow the directions that come with the appliance, so if the instructions say to use dedicated circuit then you must to meet NEC.

Since your microwave pulls 1580 Watts or around 13 Amps, this is over the limit and lighting cannot be added to this branch. Especially since it is 14/2.

You mentioned using dishwasher or disposal branch. If dishwasher is less than 10 Amps then no problem adding disposal to dishwasher branch if 12/2 wire. My dishwasher pulls 9.9 Amps for example. Otherwise, AHJD can deviate and typically will.

Assuming both Disposal and DW have dedicated 12/2 lines and depending on amperage of your dishwasher, I would most likely recommend using your DW or disposal branch.

Of course, best practice and to meet code would be to run a new 12/2 wire from your main panel to you new microwave.

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whyohwhyoh

 

What if I removed the lights and sockets that are currently attached to the 15 amp microwave line and split them up. I can put the main kitchen light and dining room light and socket with the dishwasher 14/2 circuit and combine the Breakfast nook, small pantry light with the disposal unit. That way I have a lone 15amp 14/2 circuit for the microwave - as required by the microwave instructions. Is this within codes and am I over my limit?

 

Probably not a good idea to put lighting on dishwasher branch, since dishwasher is definetly over 7.5 Amp load. (50% limit on 15A branch for fastened in place appliances).

You may meet code if you tap all lights off the disposal branch if your disposal is rated for less that 7.5 Amps. Although you may have slight dimming of lights when you run the disposal, which a home inspector may note when you sell the house.

Better idea would be to power the kitchen lighting from a power source (light or outlet) that is outside the kitchen/dining/pantry area.

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whyohwhyoh