Derating

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SEO

Senior Member
Location
Michigan
This would be a tough proposal to get thru. Not all travlers in 3-way and 4-way switching are carring current at the same time but we sure don't want to(and can't) call it load diversity, might be best to let alone and derate as we do now. JMO.
 

Smart $

Esteemed Member
Location
Ohio
This would be a tough proposal to get thru. Not all travlers in 3-way and 4-way switching are carring current at the same time but we sure don't want to(and can't) call it load diversity, might be best to let alone and derate as we do now. JMO.
We could call it exactly what it is.... eh-hh-h-h... what was I saying? ;)

Seriously though, these would be limited-power current carrying conductors, such as travellers which of a pair, only one nominally carries current at any instance. The other is as discussed... multiple switched circuits fed by a single CCC. Perhaps there are others I've not thought about.

Anyway, it appears to be too late for the 2011 cycle (unless you know or can impress someone with a good deal of clout :grin:)
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Assuming that the derating concept is based on the full load of the circuit then it may be possible to state that switch legs of the same circuit need be counted only once. There is no way that you could legally load the switch legs higher then the capacity of the circuit. Thus, a single circuit feeding a bank of 10 switch would only count as 2 current carrying conductors. If you had 2 circuits with 5 switches on each one then you would have 4 CCC's. Seems reasonable......????
 

Smart $

Esteemed Member
Location
Ohio
Assuming that the derating concept is based on the full load of the circuit then it may be possible to state that switch legs of the same circuit need be counted only once. There is no way that you could legally load the switch legs higher then the capacity of the circuit. Thus, a single circuit feeding a bank of 10 switch would only count as 2 current carrying conductors. If you had 2 circuits with 5 switches on each one then you would have 4 CCC's. Seems reasonable......????
That's how I see it... (which in most cases would mean it seems reasonable :grin:)
 

ceb58

Senior Member
Location
Raeford, NC
EGCs don't count in derating, so it's a moot point. ;)

From what I can gather from the OP, the three neutrals don't go to the switch, or at least they wouldn't need to. If all three neutrals do go to the switch, you've got 12 CCCs and you'll need to change to 15a breakers [30a * 50% = 15a per T310.15(B)(2)(a)]. If they don't, you've only got 6, and you can still use 20a OCDs

Yes, in this scenario the 3 neutrals go to the switch box, spliced and go back to the j-box, then go their separate ways. So there would be 12 ccc. As said the EGC is a moot point for derating.
 

Smart $

Esteemed Member
Location
Ohio
Yes, in this scenario the 3 neutrals go to the switch box, spliced and go back to the j-box, then go their separate ways. So there would be 12 ccc. As said the EGC is a moot point for derating.
Well you could drop the count to 9 if you 3-way spliced the neutrals in the j-box... and that is only if the neutral is connected to a load on the switch-box end. A dead-end neutral with no load is not a CCC, though I do understand it may be for future use and then would be counted.
 

kwired

Electron manager
Location
NE Nebraska
I have always understood this in this way-

say you have a feed to a bank of switches and 10 returns to (1 amp)loads all on one circuit in the same raceway. the feed conductor carries 10 amps each individual load conductor carries 1 amp. You must derate for eleven current carrying conductors, however ten of them that only carry 1 amp may not need to be upsized but the feed conductor possibly may need to be upsized (although with this example #12 90 degree conductors would still be acceptable) S

Someone mentioned "travelers" I assume they were talking about the pair of conductors running between two switches in a three way switch circuit. Out of each pair of "travelers" only one conductor needs to be counted for derating purposes because only one conductor can carry current at any given time. If you have all four conductors of a four way switch in the same raceway you only count two as current carrying because only two will carry current at any given time.
 

Smart $

Esteemed Member
Location
Ohio
I have always understood this in this way-

say you have a feed to a bank of switches and 10 returns to (1 amp)loads all on one circuit in the same raceway. the feed conductor carries 10 amps each individual load conductor carries 1 amp. You must derate for eleven current carrying conductors, however ten of them that only carry 1 amp may not need to be upsized but the feed conductor possibly may need to be upsized (although with this example #12 90 degree conductors would still be acceptable) S

Someone mentioned "travelers" I assume they were talking about the pair of conductors running between two switches in a three way switch circuit. Out of each pair of "travelers" only one conductor needs to be counted for derating purposes because only one conductor can carry current at any given time. If you have all four conductors of a four way switch in the same raceway you only count two as current carrying because only two will carry current at any given time.
I agree, the logic is there...but where does it state this in the code?
 
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