Does my microwave REALLY need to be on its own circuit?

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  #1  
Old 01-20-21, 11:16 AM
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Does my microwave REALLY need to be on its own circuit?

I live in a house built in the 1980s. I never noticed until recently but when I run the microwave, the lights in the laundry & bathroom flicker.

My boyfriend has explained to me that it should be on its own circuit and the house wasn’t designed for such a big microwave in the 80s.

He has no intention of doing this so my question is, is this a fire hazard or do we just risk tripping the breaker?
 
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Old 01-20-21, 11:50 AM
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Do the lights flicker continuously while the MW is operating? Or just when it starts up and then again when the klystron tube (the thing that makes the microwaves) cycles on and off while cooking (you can hear the sound of the MW change)?

If the former then you may have a loose or backstab connection somewhere in the circuit and it should be investigated.

If the latter (especially if the lights are LED) then no problem and you can rely on the circuit breaker to prevent a problem if the circuit becomes overloaded.

If possible a separate circuit is desirable but not necessary.
 
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Old 01-20-21, 12:37 PM
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If you run a hair dryer or iron in the laundry room while the Micro is running and the breaker holds for more than 3 minutes or so, convenience wise and safety wise you likely are good to go.
 
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Old 01-20-21, 12:42 PM
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I'm not an electrician but depending on the size (watts) of your microwave and whatever else is sharing the circuit, the circuit might be overloaded. If you have a large microwave oven, fixed in place (i.e. over the range) it should be on a dedicated circuit. I think that is an NEC requirement for an attached appliance. However, the install instructions for my over the range simply "recommends" a dedicated circuit.

There is a lot of internet confusion regarding microwave wattage as it relates to current load. Most people seem to think that the wattage rating is directly based on load (P=IE). I'm not sure that this is the case. I always thought that the wattage rating of a microwave was related to cooking power not current draw.

I'm sure one of the electricians here will have the correct answer.

 
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Old 01-20-21, 02:04 PM
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However, the install instructions for my over the range simply "recommends" a dedicated circuit.
Mine says the same thing. But I interpret it as a must vs "nice if you can do it". However, mine is not on a dedicated circuit and I have no problems.

"Observe all governing codes and ordinances. A 120-Volt, 60-Hz, AC-only, 15 or 20-amp fused electrical supply is required. A time delay fuse is recommended. It is recommended that a separate circuit, serving only this appliance, is provided."
 
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Old 01-20-21, 03:14 PM
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The light flickers continuously.
 
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Old 01-20-21, 03:26 PM
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The microwave might be failing and drawing higher than normal current pulses.
 
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Old 01-20-21, 03:31 PM
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The light flickers continuously
Then you have a problem. Possibly with the microwave or with the circuit. If your microwave is a plug in unit, can you unplug it and using a heavy duty extension cord plug into another circuit as a test?
 
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Old 01-20-21, 05:08 PM
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How old is the Microwave what is the make/model?

As a test get a long 12/3 AWG/3C conductor extension cord.
Before buying or making a cord though you can put some water in the microwave (never run any microwave oven empty it will damage it) put it on a cook cycle but don't do full power (Power level 100 %) do like 80 or 90% (again make/model will help or read the book) you can then hear the magnetron (microwave generator) this is noticeable when running as the microwave makes a loud buzzing noise from this part.

Ask your friend if the lights only flicker when the magnetron is on or all of the time.

Anyway also check the receptacles for back-stabs move to the screws or better yet get new (hopefully non "Tamper Resistant" I hate those damn stupid junk things) back wired receptacles (not back stabbed the back wire ones use pressure plates that are tightened by the side screws)
 
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Old 01-20-21, 05:13 PM
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Do a test..... plug a blow dryer in the receptacle where the microwave is normally plugged in.
Does the same flickering problem occur when you turn the dryer on ?

It would be pretty rare for a microwave to cause the lights to flicker continuously.
 
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Old 01-20-21, 05:14 PM
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A properly working 1 kw microwave should heat one pint of tap water to boiling in 170 seconds but the tests online may call for a 1 qt. test.

I've never done this test on ours (let sleeping dogs lie).
 
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Old 01-21-21, 09:37 AM
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Thanks everyone. Something else I noticed. It does not make the lights flicker EVERY single time.
 
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Old 01-21-21, 10:37 AM
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If it flickers only when the magnetron engages then you're most likely OK.
 
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Old 01-21-21, 11:23 AM
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If it flickers only when the magnetron engages then you're most likely OK.
yes as the magetron is what draws most of the input power rating but I would still check the receptacle for poor/loose connections anyway.
 
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Old 02-15-21, 12:16 PM
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Just an observation here: I have a large microwave on the same circuit as other kitchen appliances. No lights flicker when it cycles on/off. I would suspect poor/oxidized contacts somewhere along the line. If the lights are on a separate circuit breaker from the kitchen outlet, then the problem may be in the breaker box. TIme for an electrician, if that's the case.
 
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Old 02-16-21, 05:03 AM
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My microwave was tripping its circuit here and there. Inconvenient, had to go down into dark basement to reset. Both were on the same circuit.

Put the microwave and basement lights on a different same rated circuit. still tripped the breaker here and there. Installed dedicated 20 amp circuit for the microwave, still tripped here and there.

Bought a new microwave - has not tripped for 10 months since I bought it.
 
 

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