Microwave

[Fudog]

Should a microwave oven have a dedicated line with a 20 amp breaker? I just replaced our old microwave that went bad with a whirlpool convection microwave and now the breaker trips when using the convection oven. currently there is a 15 amp breaker with 14 guage wire. Also on this circuit there is the kitchen light and another outlet. Thanks

 

[sirsloop]

idk what kinda microwave you got that needs a dang 20A dedicated circuit! HAHA! I run a HUUUGEEEE 1200W sharp carousel off a 15A shared no problem. You'd need around a 2000W microwave to hit 16A on a 20A circuit.

 

[r_olson_06]

Most microwaves should have a deciated 20amp circuit. Code now requires at least 2-20amp circuits dedicated for kitchen appliances. The circuit it is on is probley just a general purpose circuit because the lighting can not be on the same circuit as these deciated circuits. Remember to use 12AWG for these 20 amp circuits.

 

[sirsloop]

that's bonkers... even the biggest non-commercial microwaves are not gonna hit 12A.

I guess its one of those things... there's code, then there's what makes sense.

 

[Charles (in GA)]

Folks need to read to OP's post......

Its a CONVECTION microwave. Heating elements PLUS the microwave tube.

Yes, it needs to be on its own dedicated circuit. They work much better when they have full voltage and the circuit is not loaded to capacity.

Charles

 

[Speedy Petey]

Folks need to read to OP's post......

Its a CONVECTION microwave. Heating elements PLUS the microwave tube.

Yes, it needs to be on its own dedicated circuit. They work much better when they have full voltage and the circuit is not loaded to capacity.

Charles

Bingo!

 

[nehog]

Should a microwave oven have a dedicated line with a 20 amp breaker?...

Also on this circuit there is the kitchen light and another outlet. Thanks

Yes, dedicated circuit!

Because that 'other outlet' could have a toaster oven on it, for example.

No electrician should ever install a 15 receptacle in a kitchen!

 

[sberry]

Yes, it needs a 20

 

[Norcal]

Yes, dedicated circuit!

Because that 'other outlet' could have a toaster oven on it, for example.

No electrician should ever install a 15 receptacle in a kitchen!

15A circuits for the dishwasher & disposal is fine. I do 20A but 15A will not cause the world to stand still.

 

[Gary S]

No electrician should ever install a 15 receptacle in a kitchen!

I totally agree with that, and I'd take it one step farther and say that nobody should ever install a 15 amp receptacle circuit anywhere. There is no receptacle circuit I know of where a 15 amp circuit will work better than a 20 amp circuit. Light circuits are fine at 15 amp, but not receptacles.

 

[wellpoison]

Yep 15 amp for lighting, 20 for receptacles. In a kitchen code requires at least 2 dedicated 20 amp receptacles (meaning no other outlets). Depending on the kitchen size I usually do 3 or 4, you never know where someone wants to put something. Usually all receptacles are 20 amp but are not dedicated they may have a bunch of receptacles hooked to one circuit. Remember to use 12 awg for 20 amp and 14 awg for 15 amp.

 

[madstat]

Fudog, the installation instructions will tell you exactly what you need. What's your model number? I bet they have them online and you can check. This almost certainly needs a dedicated 20 amp circuit.

Madstat

 

[Norcal]

Yep 15 amp for lighting, 20 for receptacles. In a kitchen code requires at least 2 dedicated 20 amp receptacles (meaning no other outlets). Depending on the kitchen size I usually do 3 or 4, you never know where someone wants to put something. Usually all receptacles are 20 amp but are not dedicated they may have a bunch of receptacles hooked to one circuit. Remember to use 12 awg for 20 amp and 14 awg for 15 amp.

Care to cite the NEC article? All that is required is the 2 small appliance branch circuits, which the fridge is allowed to be part of, if no DW, or disp. that is all that is required.

110.3(B) requires manufacturers instructions as to listing & labeling be followed, reading instructions is always good.

 

[Norcal]

Yep 15 amp for lighting, 20 for receptacles. In a kitchen code requires at least 2 dedicated 20 amp receptacles (meaning no other outlets). Depending on the kitchen size I usually do 3 or 4, you never know where someone wants to put something. Usually all receptacles are 20 amp but are not dedicated they may have a bunch of receptacles hooked to one circuit. Remember to use 12 awg for 20 amp and 14 awg for 15 amp.

Care to cite the NEC article? All that is required is the 2 small appliance branch circuits, which the fridge is allowed to be part of, if no DW, or disp. that is all that is required. The NEC is a minimum standard, there is no problem exceeding the requirements, but there is a excess of the "Urban Legend Codes".

110.3(B) requires manufacturers instructions as to listing & labeling be followed, reading instructions is always good.

 

[Speedy Petey]

Care to cite the NEC article? All that is required is the 2 small appliance branch circuits, which the fridge is allowed to be part of, if no DW, or disp. that is all that is required. The NEC is a minimum standard, there is no problem exceeding the requirements, but there is a excess of the "Urban Legend Codes".

This is what happens when arm chair electricians give advice outside their level of expertise.

 

[Socophreak]

idk what kinda microwave you got that needs a dang 20A dedicated circuit! HAHA! I run a HUUUGEEEE 1200W sharp carousel off a 15A shared no problem. You'd need around a 2000W microwave to hit 16A on a 20A circuit.

The 1200W microwaves you commonly see in subway run a 20A plug.

Does OP care to have a model number of said microwave. He's calling it a convection microwave. Does it possibly have elements in it? Or is it just one of those units that sits above the range and has a blower motor in it for the hood function? That will draw extra load above and beyond the microwave. It's impossible to say if this is normal or not without actually knowing WHAT you have.

 

[nehog]

Just for the record, most microwave ovens (non-convection, just the typical microwave oven) are between 60 and 70% efficient. So a 1100 watt rated microwave would draw about 1800 watts of current from the line, or with a nominal 120 volt circuit, 15 amps (assuming 65% efficiency.) I've not included issues such as power factor either which will effect the power requirements too...

Bottom line: microwave ovens are not terribly efficient!

 

[Speedy Petey]

So a 1100 watt rated microwave would draw about 1800 watts of current from the line,

Wouldn't that be the other way aorund.
An 1100 watt rated micro will draw 1100 watts, but only give you 700 watts of power.

 

[wellpoison]

Care to cite the NEC article? All that is required is the 2 small appliance branch circuits, which the fridge is allowed to be part of, if no DW, or disp. that is all that is required. The NEC is a minimum standard, there is no problem exceeding the requirements, but there is a excess of the "Urban Legend Codes".

I guess my post was a little miss leading. I should've said dedicated to that room. The two 20 amp branch circuits shall supply all countertop and wall receptacles, refrigeration, etc. NEC 210.52(b)(1). but they cannot have any other outlets. NEC 210.52(b)(2). All other circuits in a house usually supply more then one rooms receptacles.

 

[nehog]

Wouldn't that be the other way aorund.
An 1100 watt rated micro will draw 1100 watts, but only give you 700 watts of power.

Nope, directly from a sampling of microwave oven specifications... The rating on a microwave is the magnetron's output power, not the oven's input power.

 

[Zeke]

I've seen several microwave/convection combos. The heating elements are causing the trippage. New high end micro/convection can use both processes at once cooking the food from the inside while also cooking from the outside.

These things might be the wave of the future. They ain't cheap.

 

[Charles (in GA)]

Micro/convection combos used to be common. I have a real nice, about 25 year old Quasar combination unit. I really liked it. Great for baking a small batch of biscuits or a small pizza, or broiling a steak. It worked great till part of the touch pad ceased to function and its too old to get parts for, so a perfectly good microwave is junk. I've noticed a resurgence popularity for the convection/microwave combinations.

Charles

 

[Highbeam]

Regular non-countertop microwaves take lots of juice. I installed a seperate 20 amp dedicated circuit for my microwave I installed to replace an old vent hood. Fairly certain the instructions required the 20 amp dedicated circuit.

Even if that ****** only uses 15 amps aren't you supposed to oversize the circuit? The microwaves do plug in but they are essentially hardwired.

 

[Speedy Petey]

Nope, directly from a sampling of microwave oven specifications... The rating on a microwave is the magnetron's output power, not the oven's input power.

I guess I can't see how an appliance (ANY appliance) is rated for a certain wattage, yet draw more current that what is on the rating plate.

 

[Speedy Petey]

Even if that ****** only uses 15 amps aren't you supposed to oversize the circuit?

No, you are not "supposed" to oversize anything. Circuits are sized according to the load served and the condition of the appliance. Fixed in place, shared circuits, etc.

The microwaves do plug in but they are essentially hardwired.

Plug-in is plug-in. Hard wired is hardwired.
Fixed in place or not is a similar thing.
It either is or isn't.

 

[pop pop]

OP should check the instructions as stated. My unit is also a convection/microwave and is on a 20 amp dedicated circuit as it required. Great appliance too!

 

[rburke65]

What does the mfg. tag on the back of the unit say? For how many watts is it rated ?

 

[Fred43]

Sirsloop,
I have fifty years as an electrician and 37 years as an Electrical Contractor - shop owner.
Your reasoning may be correct in that the microwave might not draw enough to overload a 20 amp circuit. There are three other factors to consider beside common sense. It is in the NEC that any outlet added to a Kitchen, Dining area or Dining room be wired to 20 amp capacity. Secondly if you are doing this work without an inspection it is best to play it safer than just meeting code so that there is less chance of problems. Thirdly, if there was a problem resulting in an insurance case, at least they cannot blame this work if installed correctly. Liability is a big thing with Wire inspectors, insurance adjusters and fire marshals. For $5 extra dollars of materials -Please BE SAFE!!!
Fred

 

[nehog]

I guess I can't see how an appliance (ANY appliance) is rated for a certain wattage, yet draw more current that what is on the rating plate.

So you buy a 35" television... The width of the television itself is not 35 inches. The 700 watt, 1100 watt, etc., rating of a microwave is the output power and the label (should) say that clearly. Or you buy a stereo amplifier with 200 watts output, it will draw much more than 200 watts when you are driving it to full output, as it is not 100% efficient. Same for the microwave...


As to power consumption ratings, there is always a label/plate on the back near the cord that lists exactly how much power it draws from the outlet.

 

[Speedy Petey]

As to power consumption ratings, there is always a label/plate on the back near the cord that lists exactly how much power it draws from the outlet.

THAT'S my point. It CANNOT draw more than the rating plate states. Not unless there is a problem with the unit.

 

[nehog]

THAT'S my point. It CANNOT draw more than the rating plate states. Not unless there is a problem with the unit.

You leave me (and I think others) confused. No one is saying it is drawing more than the name plate states. What I say is that a nominally rated 1100 watt microwave oven (which is what you will see on that sticker when you buy it...) draws much more than 1100 watts input from the line. There are many inefficiencies in the system (transformer, magnetron, etc.) that waste input power. IOW, the thing is never, ever going to be 100% efficient.

 

[Speedy Petey]

You leave me (and I think others) confused. No one is saying it is drawing more than the name plate states.

Well it seemed to me that is exactly what you were saying here:

Just for the record, most microwave ovens (non-convection, just the typical microwave oven) are between 60 and 70% efficient. So a 1100 watt rated microwave would draw about 1800 watts of current from the line, or with a nominal 120 volt circuit, 15 amps (assuming 65% efficiency.)

No worries. I get the impression we both know what we're talking about, but are expressing it differently.

 

[sirsloop]

might as well put a GFCI receptacle on there... dont want little Jimmy to spray the receptacle down with the dish hose sprayer thing and get zapped ya know while we are in the mood to spend some cash and all! HAHAH

 

[sberry]

I have seen good micros trip a 15, if its built in I would certainly want a circuit, an extra wire and breaker doesn't mean squat in most cases. When I moved to older home only made a couple wire changes but one was running a piece of 12/3 for 2 new circuits on the counter tops. Most heavy draws I use these circuits, straight from the panel, not hooked in the existing building wiring with who knows how many junctions, etc.

I also do not have an issue with the cheap recepts, have hundreds of them in service, even some with fairly high duty cycle and cant recall the last time I had a problem with one.

 

[Fudog]

I thank everyone for the input and I will be putting a dedicated circuit in with a 20 amp breaker. Thanks!