Branch Circuits rating

[brother]

kinda had an 'interesting' convo with another person today. I try to tell them that the branch circuit rating is what the 'overcurrent' device is . they claim its the wire size even if the overcurrent device is smaller. Im having a brain spasm and cant seem to find in the code where it says this. been looking in 210, and 220. any help would be appreciated. Thanks

 

[tryinghard]

The conductors may be rated for more amperes but the circuit origin is at the OCPD and this determines the limit. These are both elements of a circuit but I say the same as you, the overcurrent protection device determines the circuit rating.

 

[brother]

The conductors may be rated for more amperes but the circuit origin is at the OCPD and this determines the limit. These are both elements of a circuit but I say the same as you, the overcurrent protection device determines the circuit rating.

do you know where this can find this in the code?? Also this applies to feeders too right??

 

[tryinghard]

I don't know of this actually being in the NEC :-? You may look in Article 240 but I really don?t think its there.

The ?other persons? logic is ignoring the beginning of the circuit. You can feed a 200A panel with a 100A circuit and it is just that a 100A circuit that happens to include a 200A panel at its destination.

 

[benaround]

brother, also by their logic, every time you increased wire size for V.D., the

size of the circuit would also increase ? Have them explain that to you.

 

[brother]

brother, also by their logic, every time you increased wire size for V.D., the

size of the circuit would also increase ? Have them explain that to you.

I know that they would not be able to explain their stance logically.
apparently this article agrees with me. The OCPD determines the 'rating of the branch circuit'.

http://ecmweb.com/nec/electric_branch_circuits_part/

 

[iwire]

do you know where this can find this in the code??

210.3

Also this applies to feeders too right??

I imagine so but can not find anything in 215 that says so.

 

[brother]

210.3.

Ok 210.3, i read right over that lol. Thanks i knew it was there.

I imagine so but can not find anything in 215 that says so.

So im not the only one that cant find it for feeders too. I also noticed that it doesnt have the 80% of the rating of the feeder restriction like branch circuits.

 

[tryinghard]

?I also noticed that it doesnt have the 80% of the rating of the feeder restriction like branch circuits.

Careful feeders are sized at the calculated load, this is the result of ?continuous" plus the "non-continuous? loads. Once this figure is known the circuit can be sized at it just not over it.

Branch circuits are the same. The 80% on a branch is really 125% of the ?continuous? load but not ?non-continuous?. Lightning is calculated at continuous, and continuous is defined as ?the maximum current is expected to continue for 3 hours or more.?

I actually had a microwave with a label of 2400W, 120V, & 20A circuit, that?s 100%. It is not a continuous load and it really does draw 18 plus amps when used. I did install #10?s but the circuit breaker is 20A, the factory cord is 20A as well. This lines up with Article 422 for Appliances (422.10)

 

[M. D.]

Careful feeders are sized at the calculated load, this is the result of ?continuous" plus the "non-continuous? loads. Once this figure is known the circuit can be sized at it just not over it.

:-? So if the calculated load of my second floor is 30 amps I can't run a sixty amp feeder to the panel:-?

 

[charlie b]

Once this figure is known the circuit can be sized at it just not over it.

That should have read, "at it, just not UNDER it."

 

[charlie b]

Also this applies to feeders too right??

I imagine so but can not find anything in 215 that says so.

So I?m not the only one that can?t find it for feeders too.

Why would feeders need to be given ?ratings,? in the same sense that a branch circuit can be rated as, for example, a ?20 amp branch circuit?? I see a reason for a branch circuit to be rated. It is so that we can distinguish between the minimum requirements for, let us say, a Small Appliance circuit, from those of a lighting circuit. But there is no code that says a dwelling unit must have a feeder for any specific purpose. Many have no feeders at all. You go from the service panel to branch circuits, and that is all there is.

 

[brother]

:-? So if the calculated load of my second floor is 30 amps I can't run a sixty amp feeder to the panel:-?

I just about the asked the same thing!!

 

[tryinghard]

:-? So if the calculated load of my second floor is 30 amps I can't run a sixty amp feeder to the panel:-?

Yep you sure can! But you cant run a 29A feeder, with a 25A or less breaker.

 

[tryinghard]

That should have read, "at it, just not UNDER it."

My bad!

 

[edavis2293]

branch circuit ratings

branch circuit ratings

Section 210.3 is very specific: the circuit rating is based on the overcurrent device rating

 

[Dennis Alwon]

I can run a 14 conductor wire to an a/c that is rated 20 amps but I can put a 35 amp OCPD on it. So does that mean my circuit is rated 35 amps? I think not

 

[edavis2293]

Branch circuit rating

Branch circuit rating

Suggest you read 210.3. Branch circuit rating is 35 amps

 

[iwire]

I can run a 14 conductor wire to an a/c that is rated 20 amps but I can put a 35 amp OCPD on it. So does that mean my circuit is rated 35 amps? I think not

I am not sure that is really a branch circuit, that may be a feeder as the final OCPD is at the unit.

 

[Dennis Alwon]

Suggest you read 210.3. Branch circuit rating is 35 amps

My point was that it is not as simple as 210.3. Perhaps by definition but to say a circuit is rated 35 amps with a 14 conductor wire is, imo, misleading. I understand what 210.3 says-- I am not sure I like it.