I am installing a new Over the Range Microwave Oven in my kitchen. I have already installed a dedicated outlet box with a 15 amp outlet (14/2 wire) to plug the oven into (nothing but the microwave will be plugged in to the outlet). The installation Instructions for the oven say the oven should be plugged in to a 20 ampere branch circuit single grounded outlet. The Installation Manual for the oven states that the electrical requirements are 14.8 amps and 1.7 kilowatts.

My question is, do I need to remove the 15 amp outlet that is already installed and replace it with a 20 amp outlet (and run 12/2 wire) or will the Microwave oven operate just fine plugged in to a 15 amp outlet? If possible, I like to use the 15 amp outlet and avoid having to run new 12/2 wire to the box. But if necessary for the oven to operate properly, I'll do the extra work.

If anyone knows the answer, please advise. Thank you. Dan

Yes the microwave will need the complete 20 amp circuit. The circuit needs to be 125 % of the running load amps, 14.8 * 1.25= 18.5 amps. Round up to the next standard size breaker.

Dan,

One thing that's not clear (to me at least) in your question: you mention 15 amp and 20 amp outlets but you don't mention the circuit breakers. A dedicated circuit would include the circuit breaker at the main service panel, the wiring to the outlet, and an outlet rated at the appropriate amperage.

You probably understand that already but I just want to make sure because, for instance, installing a 20 amp outlet running off a 15 amp circuit breaker would mean that the breaker might trip prematurely, and the opposite condition (15 amp outlet installed off a 20 amp breaker) would be very dangerous because the circuit breaker might not trip even if the maximum amperage rating of the outlet was exceeded--serious fire/shock hazard.

As to your main question I have two observations:

1) based on the 14.8 amp requirement in the installation instructions I would say that you can probably squeak by with the 15 amp circuit as most decent engineers will specify a slightly higher current (i.e. amperage) rating then what is actually required, just to be safe. That probably explains why the installation manual specifies a 20 amp circuit. They are allowing that 25% margin of error.

2) If it were me, I would probably bite the bullet and run the 20 amp circuit because I like to have a good margin when it comes to electrical stuff, and because my observation has been that circuit breakers tend to trip a little easier as they age.

Good Luck

--John