# branch circut



## RePhase277 (Feb 5, 2008)

zen said:


> how can it be ok to jump off of an oven circut to add say a microwave plug ,, from one of the legs.the oven having a 40 amp breaker.i understand that a 25 amp breaker on a no 12 can cause the sheathig to melt off before tripping so why would it not if it was jumped from a oven circut


It is not OK to tap a 40 A circuit to supply a microwave receptacle. Who told you that?

And 25 A on #12 will not "cause the sheathing to melt off". That will barely make it warm.


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## zen (Jun 15, 2009)

i will find out and reply


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## Magnettica (Jan 23, 2007)

You might be able to do this.

210.10 (A)(3) Exception #1


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## raider1 (Jan 22, 2007)

Magnettica said:


> You might be able to do this.
> 
> 210.10 (A)(3) Exception #1


I think you mean 210.19(A)(3) Exception #1

IMHO a microwave receptacle does not meet the requirements of that exception and can't be tapped from a 50 amp cooking appliance branch circuit.

Chris


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## Magnettica (Jan 23, 2007)

raider1 said:


> I think you mean 210.19(A)(3) Exception #1
> 
> IMHO a microwave receptacle does not meet the requirements of that exception and can't be tapped from a 50 amp cooking appliance branch circuit.
> 
> Chris


Yes, 210.19. 

How come? What do they mean by a "counter-mounted electric cooking unit"?


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## Bob Badger (Apr 19, 2009)

Magnettica said:


> Yes, 210.19.
> 
> How come? What do they mean by a "counter-mounted electric cooking unit"?


The handbook shows a stove top unit recessed in a counter, that is about the only appliance I can imagine that would be listed to be supplied with a 50 amp circuit.

As far as the micro you can not supply a 15 or 20 amp receptacle from the 50 amp range circuit.


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## Magnettica (Jan 23, 2007)

Bob Badger said:


> The handbook shows a stove top unit recessed in a counter, that is about the only appliance I can imagine that would be listed to be supplied with a 50 amp circuit.
> 
> As far as the micro you can not supply a 15 or 20 amp receptacle from the 50 amp range circuit.


Recessed in the counter would definitely qualify as counter-mounted. 

For the record, I would never wire a receptacle for a microwave from an old 50-amp line, but it does make for an interesting discussion.


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## raider1 (Jan 22, 2007)

I agree with Bob.

If you could find a microwave that came with a 20 amp supply whip instead of a cord and plug there might be an argument that it could meet the exception #1 to 210.19(A)(3).

Chris


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## zen (Jun 15, 2009)

one of the guys i work with went to a service call and thats what someone had done, my boss explained someone had mis interpreted the tap rule ,,obviously this is over my head so i posted it here. he said there are situations when it can apply but not to do it any time in my future


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## micromind (Aug 11, 2007)

Installing a 15 or 20 amp receptacle on a 50 amp circuit would violate 210.21(B)(1), if it's a single receptacle. The only exceptions are for motors and welders. 

If it's a duplex, it'd violate 210.21(B)(3). 

I don't know of any time you can feed a receptacle with a circuit larger than the rating of the receptacle, except 15 amp duplexes on 20 amp circuits. A single can be fed with a circuit smaller than its rating, not larger. 

Rob


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## Magnettica (Jan 23, 2007)

micromind said:


> Installing a 15 or 20 amp receptacle on a 50 amp circuit would violate 210.21(B)(1), if it's a single receptacle. The only exceptions are for motors and welders.
> 
> If it's a duplex, it'd violate 210.21(B)(3).
> 
> ...



I've come to realize the error I made and I understand that the branch circuit ampacity cannot exceed the rating of the receptacle. I knew this, and forgot to apply it. May I be excused?


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## Buddha In Babylon (Mar 23, 2009)

zen said:


> how can it be ok to jump off of an oven circut to add say a microwave plug ,, from one of the legs.the oven having a 40 amp breaker.i understand that a 25 amp breaker on a no 12 can cause the sheathig to melt off before tripping so why would it not if it was jumped from a oven circut


 
Firstly, nice name dude. Do you practice?

Secondly, i heard a story from my foreman the other day about a circuit he tested in a buddy's house that had like a third of the entire residences load on it. number 12. Said he read 83 AMPS! i didn't believe him at the time, but as i understand, a number 12 can carry an insane amount of current before it disintegrates. As in fault conditions.


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## steelersman (Mar 15, 2009)

Buddha In Babylon said:


> Firstly, nice name dude. Do you practice?
> 
> Secondly, i heard a story from my foreman the other day about a circuit he tested in a buddy's house that had like a third of the entire residences load on it. number 12. Said he read 83 AMPS! i didn't believe him at the time, but as i understand, a number 12 can carry an insane amount of current before it disintegrates. As in fault conditions.


And he said 83 amps was only a third? Hahahaha! Not! Well maybe if the residence was Bill Gates' mansion or something huge like that. Most homes will hardly ever ever see a load of 83 amps on the entire panel at once!


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## Flash (Apr 29, 2009)

Article 100 defines "Cooking Unit, Counter-Mounted". Unless there are one or more heating elements a microwave will not meet the definition.


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## kbsparky (Sep 20, 2007)

There are microwave oven appliances that have heating elements in them, and have convection oven capacity.

SO, according to that definition, would it be allowable under the exception to tap such an appliance off the range circuit? Why or why not?


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## Flash (Apr 29, 2009)

Great Question.. The definition lists, heating elements, internal wiring, and built in or mountable controls only. Microwaves may have elements, but they also have "Generators" (UL definition) and other components beyond the three listed.


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## micromind (Aug 11, 2007)

If the microwave were hard-wired and contained heating elements, it would very likely meet the exception. If it's cord-and-plug, it wouldn't.

I'm not aware of any exception that allows more than a 20 amp circuit to feed a 15 or 20 amp receptacle. If there is one, I certainly can't find it.

Rob


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## Larry Fine (Oct 24, 2007)

micromind said:


> A single can be fed with a circuit smaller than its rating, not larger.


You can't supply a 20a receptacle with a 15a circuit. The slot configuration specifies that the circuit is capable of supplying the 20a.


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## Larry Fine (Oct 24, 2007)

Buddha In Babylon said:


> ... a number 12 can carry an insane amount of current before it disintegrates. As in fault conditions.


Or as emergency-replacement soldering-gun tips.


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## RePhase277 (Feb 5, 2008)

Larry Fine said:


> You can't supply a 20a receptacle with a 15a circuit. The slot configuration specifies that the circuit is capable of supplying the 20a.


Sure you can. A single receptacle anyway. In my opinion, it is a flub in the wording of the code, but it is there nonetheless. 

*210.21(B)*: A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.

Well, 20 is not less than 15, so the Code allows a 20 A receptacle on a 15 A circuit.


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## Larry Fine (Oct 24, 2007)

InPhase277 said:


> Well, 20 is not less than 15, so the Code allows a 20 A receptacle on a 15 A circuit.


How about even higher, like a range receptacle?


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## RePhase277 (Feb 5, 2008)

Larry Fine said:


> How about even higher, like a range receptacle?


Sure, people put range receptacles on 40 A circuits all the time. But the wording of the code seems to indicate that you could put a range receptacle on a 15 A circuit if you wanted to. Don't know why you would, but it seems permissible.


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