Understanding Upsizing breaker 240.4

[electricg]

Does anyone know why its allowed to upsize a breaker for one receptacle, but not for more than 1 in 240.4(B)(1)? What was the theory or reasoning behind this?

As I understand it, most receptacles are duplex receptacles so if you are using this then you would not be able to upsize even when it's border line.

for example, #10 wire derated at 70% because of 9 ccc in conduit puts it at 28 amps. Circuit has to be protected at 20 amp breaker not 30.

 

[charlie b]

I think the key to understanding this article is to note that it deals with plug and cord connected equipment. When we perform load calculations, receptacles are counted at 90 VA each. But receptacle outlets are used by plugging in whatever the owner wants to plug in. So there really is no control over how much load will actually be served by the circuit. 90 VA is a good overall average, but not an accurate design parameter when it comes to actual usage. If there are a number of places to plug stuff in, then the actual load can exceed the ampacity of the conductors. If there is only one place to plug stuff in, then that risk is not as high. Such, at least, is my guess.

 

[electricalist]

220.14 I says 180 va per yoke for commercial

 

[charlie b]

220.14 I says 180 va per yoke for commercial

And there are two receptacles on a single yoke, so each receptacle is worth 90VA.

 

[iceworm]

And there are two receptacles on a single yoke, so each receptacle is worth 90VA.

And a single receptacle on a yoke is worth .... ?

Later All - Got to go back to work - got someone paying for my time

ice

 

[electricalist]

Nice, so if it was a load calculation I would use 90 va for a single outlet and 180 va for a duplex and keeping in mind the single would need to be 20 amp rated if in commercial.

 

[electricg]

And a single receptacle on a yoke is worth .... ?

Later All - Got to go back to work - got someone paying for my time

ice

Point taken. a single receptacle on a single yoke would be 180va. So its based off of yokes and not the receptacle. But it is interesting to see NEC allow the upsizing when it is a single receptacle.

 

[Strathead]

Does anyone know why its allowed to upsize a breaker for one receptacle, but not for more than 1 in 240.4(B)(1)? What was the theory or reasoning behind this?

As I understand it, most receptacles are duplex receptacles so if you are using this then you would not be able to upsize even when it's border line.

for example, #10 wire derated at 70% because of 9 ccc in conduit puts it at 28 amps. Circuit has to be protected at 20 amp breaker not 30.

Am I missing the boat again? I read the comments and I am confused. Unless your code book is different than mine, 240.4(B) allows you use the next higher standard size breaker. Subsection (1) refers to this not being allowed for a multi-wire branch circuit. That has nothing to do with the number of receptacles on the circuit.

 

[templdl]

Am I missing the boat again? I read the comments and I am confused. Unless your code book is different than mine, 240.4(B) allows you use the next higher standard size breaker. Subsection (1) refers to this not being allowed for a multi-wire branch circuit. That has nothing to do with the number of receptacles on the circuit.

I find it interesting when I see questions and discussions such as this to just sit back and watch. Your reply is the first one th as t makes sense. Breakers protect wire, wire must be sized to carry the load.
When the wire size is established then a breaker is selected to protect the wire based upon the ampacity of the wire and not the load. Should the not be a standard breaker size that is the same as rated ampacity of that of the wire you then are allowed to select the breaker which is the next closest above for breaker sizes up to 800a as I can recall.
So it is knowing the load first, sizing the wire which must carry the load, the sizing the breaker to protect the wire.
So the load may be based upon a given number of recepticles which would determine the wire size and then the breaker selected to protect the wire.

 

[david luchini]

Am I missing the boat again? I read the comments and I am confused. Unless your code book is different than mine, 240.4(B) allows you use the next higher standard size breaker. Subsection (1) refers to this not being allowed for a multi-wire branch circuit. That has nothing to do with the number of receptacles on the circuit.

Your code book must be different than mine. I don't see anything in 240.4(B)(1) referencing multi-wire branch circuits. I do see a reference to the number of receptacles on the circuit, though.

 

[mwm1752]

a dedicated circuit can still be a cord & plug connection. but the load of one piece of equipment does not exceed a continuous load rating 210.23(A)(1). Its not a perfect world but in the situation of having a wire derated to 16Amps for a 20 amp dedicated circuit could be used as code does not allow more than 16 amps on a plug & cord 20 amp circuit. not dedicated circuit then the conductor is required to handle up to the breaker rating of a non continuous load. IMHO

 

[electricg]

Am I missing the boat again? I read the comments and I am confused. Unless your code book is different than mine, 240.4(B) allows you use the next higher standard size breaker. Subsection (1) refers to this not being allowed for a multi-wire branch circuit. That has nothing to do with the number of receptacles on the circuit.

I agree with others, your code book must be different, I am reading the 2014 NEC. Nothing said about multi wire branch circuits on upsizing in that section of 240.4

 

[electricalist]

If you have a 20 amp breaker on a branch circuit fed by 12 awg to a recepticle. The recepticle can be rated at 15 amp because 2 cord connections can't both pull 20 amps. If the branch circuit is dedicated the device would need to be 20 amp rated and as I understand can only accept 1 cord. If this same circuit requires 25 amps for example it would then be ok to meet the amp requirements as long as it meets 240. B 1-2-3