Microwave and 210.21(B)(2)

SoonerEE

Member
Location
Mustang, OK
I have an 1800W (input) microwave connected to a 15A duplex receptacle fed from a 20A circuit breaker. My understanding is 210.21(B)(3) is what allows a 15A receptacle to be fed from a 20A circuit breaker.

Since the receptacle is a duplex, it is my understanding that this is NOT an individual branch circuit. Therefore, applying 210.21(B)(2), it seems that the maximum load the presented to the receptacle should be limited to 12A (1440W).

Is this a violation, or am I misunderstanding?
 

iwire

Moderator
Staff member
Location
Massachusetts
The circuit runs one piece of utilization equipment. It is an individual branch circuit. See article 100 for the definition.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
210.21(B)(2) doesn't say anything about "individual branch circuit."
I agree that is what the code requires, but there is no real reason for that rule to be in the code. The "guts" of 15 and 20 amp receptacles of the same brand and model are the same as each other. The only difference is "T" slot on the face of the receptacle.
 

infinity

Moderator
Staff member
Location
New Jersey
I agree that is what the code requires, but there is no real reason for that rule to be in the code. The "guts" of 15 and 20 amp receptacles of the same brand and model are the same as each other. The only difference is "T" slot on the face of the receptacle.

Good point. :thumbsup:
 

Greg1707

Senior Member
Location
Alexandria, VA
Occupation
Business owner Electrical contractor
above range microwave

above range microwave

Is this an above the range microwave unit? Most that I have installed state they can be supplied by a 15 OR 20 amp circuit.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Why would we need to use a 20 a recept. when the device does not have a 20 amp plug?
 

SoonerEE

Member
Location
Mustang, OK
Yes, it is mounted above the range. It looks like the two options would be a 20A duplex or

So despite the internals of the receptacles being the same (15A vs 20A), the NEC seems to distinguish between the two when supplied by a 20A receptacle [per Table 210.21(B)(2)]. Specifically, the max load on a 15A receptacle is 12A, while the max load on a 20A receptacle is 16A. Any theories as to why?
 

GoldDigger

Moderator
Staff member
Yes, it is mounted above the range. It looks like the two options would be a 20A duplex or

So despite the internals of the receptacles being the same (15A vs 20A), the NEC seems to distinguish between the two when supplied by a 20A receptacle [per Table 210.21(B)(2)]. Specifically, the max load on a 15A receptacle is 12A, while the max load on a 20A receptacle is 16A. Any theories as to why?
Because once, long ago and far away, the innards of the two types were not identical?
 
Top