Microwaves

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jmellc

Senior Member
Location
Durham, NC
Occupation
Facility Maintenance Tech. Licensed Electrician
A helper recently asked me why I always put microwaves on a 20 amp circuit. I told him partly because of kitchen circuuits generally being 20 amp and partly that there might be some MW's out there that demand it. Most I have seen run from about 1,000 to 1,500 watts, where 15 amp would be OK. However, a lot of the ckts we run are for units that are not there yet. I once had to rerun a wall oven ckt where i had installed a 30A. Customer called that the unit had arrived and was 40A. Was a Bosch & sure enough needed 40. Keeping that in mind, I have always done 20 for microwaves. Better to err on side of caution IMHO.

Has anyone seen larger microwaves that run 1600 to 2400 watts?
 
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peter d

Senior Member
Location
New England
I have observed that several contractors in my area that do a lot of new homes run a 15 amp circuit to them. They are wiring based on a fixed price and every bit of savings counts.
 

JFletcher

Senior Member
Location
Williamsburg, VA
Heh, thought it was code to have a 20A circuit for a microwave. Looked up several, saw lots rated 1600W/14A.

Running a 20A circuit for the microwave vs a 15A... how much money are you going to save? Figure 50' of wire, what are you saving, $5? Receptacle, box, coverplate, staples, even the breaker are the same price. Extra 10 seconds terminating 12/2 vs 14/2?
 

Smart $

Esteemed Member
Location
Ohio
Nothing says those have to be on a 20 amp circuit. If you run a microwave for 3 or more hours, you have a very serious problem on your hands. :)
Nothing says you have to put a microwave on a 20A circuit.

However, if the receptacle is in a kitchen, I believe you'll find that you have to install it on a 20A circuit because all kitchen receptacles are required to be on small appliance branch circuits, which are required to be 20A except by exception for a 15A refrigerator circuit [210.52(B)(1)].
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
Personally speaking I wouldn't take a chance on running a 15A circuit. Obviously, if it's a table top unit you're automatically plugging into a 20A circuit but I believe we're talking about built-in units over a range or in a separate cabinet.

I was lucky enough to know,in advance, about an Advantium micro-oven that was being installed in a kitchen remodel. It was a 20A, 240V unit so 12/3 was run for that. I don't remember if the neutral was required but I ran it anyway.
 

iwire

Moderator
Staff member
Location
Massachusetts
How many of you guys are seeing residential microwaves with 20 amp plugs on them? I have not seen any.

If they have a 15 amp plug a 15 amp circuit is not risky.

That said, if it is in a kitchen I agree with smart$ it needs to be 20.
 
How many of you guys are seeing residential microwaves with 20 amp plugs on them? I have not seen any.

If they have a 15 amp plug a 15 amp circuit is not risky.

That said, if it is in a kitchen I agree with smart$ it needs to be 20.

I think I have seen a 20 amp plug like 3 times in my career - probably only in a commercial kitchen.

You make an interesting point: do you see manufacturers that provide a 15 amp plug but state in the instructions to provide a 20 amp circuit?
 

peter d

Senior Member
Location
New England
Nothing says you have to put a microwave on a 20A circuit.

However, if the receptacle is in a kitchen, I believe you'll find that you have to install it on a 20A circuit because all kitchen receptacles are required to be on small appliance branch circuits, which are required to be 20A except by exception for a 15A refrigerator circuit [210.52(B)(1)].

Using that logic, we can't run 15 amp circuits to dishwasher and disposals either, if we install receptacles under the sink for them and use cord and plug methods. I'm thinking of a fixed in place, over the range microwave or an undercounter one. Clearly, one sitting on a counter would likely just be plugged into a regular SABC. I think permanently installed microwaves are what's in view here.
 

peter d

Senior Member
Location
New England
How many of you guys are seeing residential microwaves with 20 amp plugs on them? I have not seen any.

If they have a 15 amp plug a 15 amp circuit is not risky.

That said, if it is in a kitchen I agree with smart$ it needs to be 20.

SABC's, yes. Individual branch circuits for appliances? I do not see that requirement.
 

peter d

Senior Member
Location
New England
Explain the need for the exception allowing 15 amp IBCs for refrigerators.

Because for some reason the fridge outlet is considered acceptable to be on the SABC while other outlets are not. It's your contention that every circuit in a kitchen must be 20 amps? :huh:
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Explain the need for the exception allowing 15 amp IBCs for refrigerators.

For whatever reason, the phrase "receptacle outlets for refrigeration equipment" is included in 210.52(B)(1):

2011 NEC said:
210.52(B)(1) Receptacle Outlets Served. In the kitchen, pantry, breakfast room, dining room, or similar area of a dwelling unit, the two or more 20-ampere small-appliance branch circuits required by 210.11(C)(1) shall serve all wall and floor receptacle outlets covered by 210.52(A), all countertop outlets covered by 210.52(C), and receptacle outlets for refrigeration equipment. [ . . . ]

Exception No. 2: The receptacle outlet for refrigeration equipment shall be permitted to be supplied from an individual branch circuit rated 15 amperes or greater
So without the exception, the refrigerator would need to be on an SABC. Even if the phrase "receptacle outlets for refrigeration equipment" were removed from 210.52(B)(1), the exception would still be useful, as 210.52(B)(1) also includes the wall receptacles covered by 210.52(A). A typical refrigerator receptacle would qualify as a 210.52(A) wall receptacle, unless it were mounted more than 5-1/2 feet above the floor.

Cheers, Wayne
 

iwire

Moderator
Staff member
Location
Massachusetts
For whatever reason, the phrase "receptacle outlets for refrigeration equipment" is included in 210.52(B)(1):


So without the exception, the refrigerator would need to be on an SABC. Even if the phrase "receptacle outlets for refrigeration equipment" were removed from 210.52(B)(1), the exception would still be useful, as 210.52(B)(1) also includes the wall receptacles covered by 210.52(A). A typical refrigerator receptacle would qualify as a 210.52(A) wall receptacle, unless it were mounted more than 5-1/2 feet above the floor.

Cheers, Wayne

A microwave outlet is often less than 5.5' AFF.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
A microwave outlet is often less than 5.5' AFF.

OK. Are we talking about an above the range microwave? That receptacle is usually located in a cabinet above the microwave, which means it is not subject to 210.52 per 210.52(3).

Or did you have something else in mind?

Cheers, wayne
 
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