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


  #1  
Old 01-20-21, 10:16 AM
K
Member
Thread Starter
Join Date: Jan 2021
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
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?
 
  #2  
Old 01-20-21, 10:50 AM
2
Member
Join Date: Jan 2014
Location: USA near Boston, MA
Posts: 2,251
Received 388 Upvotes on 337 Posts
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.
 
bulova voted this post useful.
  #3  
Old 01-20-21, 11:37 AM
B
Member
Join Date: Jan 2021
Location: United States
Posts: 162
Received 21 Upvotes on 19 Posts
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.
 
  #4  
Old 01-20-21, 11:42 AM
C
Member
Join Date: Mar 2007
Posts: 2,503
Received 350 Upvotes on 293 Posts
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.

 
  #5  
Old 01-20-21, 01:04 PM
Norm201's Avatar
Member
Join Date: Sep 2013
Location: United States
Posts: 10,956
Received 721 Upvotes on 640 Posts
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."
 
  #6  
Old 01-20-21, 02:14 PM
K
Member
Thread Starter
Join Date: Jan 2021
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
The light flickers continuously.
 
  #7  
Old 01-20-21, 02:26 PM
B
Member
Join Date: Jan 2021
Location: United States
Posts: 162
Received 21 Upvotes on 19 Posts
The microwave might be failing and drawing higher than normal current pulses.
 
  #8  
Old 01-20-21, 02:31 PM
Norm201's Avatar
Member
Join Date: Sep 2013
Location: United States
Posts: 10,956
Received 721 Upvotes on 640 Posts
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?
 
2john02458 voted this post useful.
  #9  
Old 01-20-21, 04:08 PM
Join Date: Jan 2009
Location: United States
Posts: 1,041
Received 78 Upvotes on 73 Posts
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)
 
  #10  
Old 01-20-21, 04:13 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,816
Received 3,922 Upvotes on 3,518 Posts
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.
 
  #11  
Old 01-20-21, 04:14 PM
B
Member
Join Date: Jan 2021
Location: United States
Posts: 162
Received 21 Upvotes on 19 Posts
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).
 
  #12  
Old 01-21-21, 08:37 AM
K
Member
Thread Starter
Join Date: Jan 2021
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks everyone. Something else I noticed. It does not make the lights flicker EVERY single time.
 
  #13  
Old 01-21-21, 09:37 AM
Norm201's Avatar
Member
Join Date: Sep 2013
Location: United States
Posts: 10,956
Received 721 Upvotes on 640 Posts
If it flickers only when the magnetron engages then you're most likely OK.
 
  #14  
Old 01-21-21, 10:23 AM
Join Date: Jan 2009
Location: United States
Posts: 1,041
Received 78 Upvotes on 73 Posts
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.
 
CasualJoe voted this post useful.
  #15  
Old 02-15-21, 11:16 AM
I
Member
Join Date: Feb 2021
Posts: 168
Received 35 Upvotes on 29 Posts
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.
 
  #16  
Old 02-16-21, 04:03 AM
A
Member
Join Date: Mar 2014
Posts: 999
Received 162 Upvotes on 135 Posts
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.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: