Raceway Fill

[Cindysparky]

So, I’ve got a question of opinion here. I’m working on this job and we are pulling all these switch legs out of a 277V lighting control panel. There’s more than just Swicth legs in the pipe. The pipe is comprised of say 2 different circuits, a couple all the time hots, and a bunch of swicth legs.

Now, I did the Math and considered all of the switch legs current carrying. The Math says that you can fit all of these in the pipe and it’s all fine and well.

My question is: if you have 1 circuit with all of these switch legs coming off of it, all sharing the same neutral in the pipe (clearly)… Doesn’t it seem like overkill to count them all as current carrying. If the circuit breaker is saying it’s only going to allow 20 amps… doesn’t it seem reasonable to count it once?

My only thought was the potential to change it. Like how we count spares.

 

[infinity]

My question is: if you have 1 circuit with all of these switch legs coming off of it, all sharing the same neutral in the pipe (clearly)… Doesn’t it seem like overkill to count them all as current carrying. If the circuit breaker is saying it’s only going to allow 20 amps… doesn’t it seem reasonable to count it once?

Reasonable yes but the NEC doesn't care about reasonable. Think about one hot leg (20 amp circuit) and 9 switch legs in the same raceway, that would be 10 CCC's even though you would divide the current across the 9 switch legs and generate very little heat the NEC still requires you to consider that 9 switch legs and 1 hot leg 10 CCC's. Pretty dumb but it is what it is.

 

[Cindysparky]

That was my thought. I thought I might just put this out in the air. There’s always another code cycle

 

[wwhitney]

I made a proposal for the 2023 NEC to add the following text to the notes at the bottom of Table Table 310.15(C)(1) "Adjustment Factors for More Than Three Current-Carrying Conductors":

"Where two or more conductors are protected by the same overcurrent device, and their currents are additive at the overcurrent device, they may be counted as a single conductor."

The proposal was rejected, with the committee statement:

"Loading and overcurrent protection could be changed in the future based on installed conductor sizes."

Which, in my opinion, is a stupid reason; the same could be said of many things in the NEC, and rules shouldn't be based on "what ifs" with respect to configuration details regulated by the NEC.

Cheers, Wayne

 

[infinity]

The proposal was rejected, with the committee statement:

"Loading and overcurrent protection could be changed in the future based on installed conductor sizes."

Which, in my opinion, is a stupid reason; the same could be said of many things in the NEC, and rules shouldn't be based on "what ifs" with respect to configuration details regulated by the NEC

Your proposal was sound and made perfect sense which is probably why it was rejected. The fact that they leaned towards the "what if" scenario makes you wonder if they even have a clue as to what it is that they're reading.

 

[ramsy]

The proposal was rejected, with the committee statement:

"Loading and overcurrent protection could be changed in the future based on installed conductor sizes."

Using equation 310.14(B) architects bypass all derating & continuous use schemes, with validated & verified thermal models described in Annex B.

Only us knuckleheads without plans are subject to idiot tables, and suffer rejection of proposals to fix them.

 

[Dennis Alwon]

@Cindysparky There is an exception for 3 way switches to not include one conductor as a 3 way switch will always have 1 wire that is not current carrying.

This is a good example of why @wwhitney rejection makes no sense. They will allow a deduction for a 3 way even though those conductors can be changed at a later date.

 

[Cindysparky]

I made a proposal for the 2023 NEC to add the following text to the notes at the bottom of Table Table 310.15(C)(1) "Adjustment Factors for More Than Three Current-Carrying Conductors":

"Where two or more conductors are protected by the same overcurrent device, and their currents are additive at the overcurrent device, they may be counted as a single conductor."

The proposal was rejected, with the committee statement:

"Loading and overcurrent protection could be changed in the future based on installed conductor sizes."

Which, in my opinion, is a stupid reason; the same could be said of many things in the NEC, and rules shouldn't be based on "what ifs" with respect to configuration details regulated by the NEC.

Cheers, Wayne

I'm impressed that you proposed this. It would be great to see this revisited. In this case, all of the switch legs originate from a lighting panel.

 

[Cindysparky]

@Cindysparky There is an exception for 3 way switches to not include one conductor as a 3 way switch will always have 1 wire that is not current carrying.

This is a good example of why @wwhitney rejection makes no sense. They will allow a deduction for a 3 way even though those conductors can be changed at a l

 

[Cindysparky]

Yeah the three way could change. Good point. I was thinking of that. Switch up the travelers purpose...