Electrical Wiring in the Home/120v/ 20amp circuit


QUESTION: New micro/convection oven calls for a 120v/20amp circuit, 12/3 wire. Sounds like I will need to install two separate breakers in the panel, one for the black and one for red? Or can this be done with one double breaker?

ANSWER: No, it needs a single breaker with wire large enough to carry 20 amps whatever distance,   and a 20 amp breaker.

It's the same as a typical 15 amp breaker only this must be one hell of a microwave.

Remember  breakers protect the wire so the wire to the microwave must be large enough for the 20 amps for whatever distance and then it is a single pole typical breaker at 20 amps.

NOW The existing wire might be big enough to handle 20 amps but I don't know the distance,  if it is good for 20 amps  then all you need is a 20 amp breaker.

A double breaker is no help because it is the wire size and each conductor must handle 20 amps.


Above has a wire chart   the distance is probably OK   not many houses have 200 feet runs, so it really boils down to what wire size is in the existing outlet,

Outlets are already parallel so we cannot combine them,  unless for some weird reason you have a double outlet on two circuits but that would a special and I doubt it,     Check your wire size in your existing outlet where you current microwave is  and maybe it is big enough,  

Another thought,   maybe trade it back in for a 15 amp unit, it depends on the age of your house most newer houses have the capacity to run 20 amp circuits,    so be sure and check,  it might be a simple thing pull a new circuit, or it might be a hell of a fight,    but most microwave circuits on newer homes are capable of 20 amps,     

Any questions or problems let me know   

---------- FOLLOW-UP ----------

QUESTION: Sorry I didn't mention that this is a remodel and a new circuit just for this micro/convection oven (about a 18 foot run). The micro has a four wire connection, ground, black, red, white. The installation directions call for 120v, 20a, 12/3 wire.  My question centers on how to connect to panel, one breaker or two?

Thanks for your response,


I completely missed micro/convection,  but this is a good question and it could go either way,  most times red means 240 is brought to the appliance and split up there, but yours says 120 volt 12/3 wire,  that suggests it is for the entire appliance,  but I don't think so,  

Can you send me the make and model so I can read the install guide,  I want to see what they are trying to do,      besides confusing the crap out of both of us,     

Manuals anymore are written in some kind of format nobody understands,    I have read that two circuits are needed on GE,  one on Samsung,  one on others but it was 240  therefore the red wire,     but like you say   are they asking you to use the red as one 120 circuit and black for the other  but with four wires, when it says three?

Send to my personal email  wbwill@sbcglobal.net     give me make model,  serial  should be enough   I will figure this out,        they got into all this neutral bonding stuff, and ever since it has been a mess for everyone,    I am OK with the theory but how they explain it is impossible sometimes,    so we want to be sure,        

Send me that info and I will figure it out and explain it    sorry I missed the convection part but it is still telling you go left and right  
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Will Babbitt


Electrical issues of all types, wiring, control, appliances, components, specialty in Electric MOTOR or APPARATUS trouble shooting, electric motors, electrical problems, single phase, three phase, DC, capacitors, elevator MG-Sets, modifications, reverse engineering, VFD Drives, single to three phase convertors. Repair of most any electrical/mechanical/electronic apparatus, OEM, AC, DC, Industrial Applications, Three phase, single phase failure mode, determining the root cause of the equipment failure BEFORE failure repeats, Antique appliances, electric motors, fans, ceiling fans, base mount fans, poor equipment performance, Modifications, habitual failures, vibration, redesign, obsolete issues, collectible items restored, rewinding. Owner of EMR Repair Inc www.emrrepair.com More information on electric motors, under Engineering/Motors Ask about any electrical or mechanical problems in the home, office, or even at your work. B2B or business to business CONSULTING I can do but it would be a much more complex issue, that would require a significant amount of time. repair@mearservice.com from there we can discuss and begin work on about anything. Industrial electric motors, controls, troubleshooting, vibration, alignment, any type of industrial or commercial electric/electrcical equipment For the home owner, renter, apartment if you have odd things going on, describe to me, photos are normally very helpful, appliances, heating and air conditioning issues, light switches, installation, DIY PROJECTS FOR THOSE NOT EDUCATED IN ELECTRICAL, we can do some things, but for safety and sanity reasons, I may refer you to a local electrician, and help you find one, help you with pricing and even speak directly with anyone you hire if you have issues,


Over thirty years with a major repair and sales company, VP of Operations, and former owner of my own specialty repair shops, MEAR Services local to Kansas City Missouri EMR Repair Inc., located in Kansas City Missouri, 2014 sold both businesses to JCI Industries, Lee's Summit Missouri wbabbitt@jciind.com Evaluation and repair of electrical/mechanical apparatus. Electrical and mechanical repairs, trouble shooting including, vibration and balance issues. About.com provides this service, and the huge costs to provide help on about any subject. They provide the servers, the people to vet the experts, costs that would be the same as operating a good sized business, They should be appreciated for what they do, the huge costs and the great help they provide for free, Electric motor questions, can be answered here but there is a dedicated category that has other experts to help and add to a solution. Other common questions, are noises in the walls, breakers tripping, devices not starting or shutting down for no apparent reason, smoke alarms buzzing, thermostat change outs, or sizing wire or needing information for a new project, but anything can be resolved, anything, with enough effort and patience, DIY, with electrical is possible, but in most cases the use of a simple ohm meter or volt meter is needed, they can be purchased at any hardware store for a few bucks. If you have smoke, or smell smoke, don't be writing me, call 911 the Fire Department has no problem looking for smoke smells, better then spraying water on a blazing fire. DO NOT GET CAUGHT INVESTIGATING AND TRAPPED IN A BASEMENT LOOKING FOR A BLOWER FAILING< As to the tip jar, it is up to you, it is appreciated, every expert spends out of pocket that I know, we spend on IP time, computer wear, printing documents, books, and of course our time, but if we prevent a $400 service call, we did well,

Former IBEW, EASA, IEEE, UL, ..............


10 plus years, various Technical Schools, followed by Industrial College Credit and non Credit Courses, electronics courses, experience in most any electrical apparatus, electric motors and generators, AC OR DC, fractional to above 5000HP, other electrical apparatus, slip rings, sleeve [plain] bearings, lubrication, identification-no data plate, control components, service and sales. I have continued night schools for decades, the list is extensive. I have been in the business of repairing most anything with wires or mechanical parts for decades, I have some helpful hints and directions you won't have to dig up. Or hopefully not have to pay a huge service call invoice to find.

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