Feeder neutral as CCC???

[chevyx92]

Situation, 3 phase 50A 4W ckt from panel to feed wiremold 3000 series that has circuit breaker housing that will have (3) 1P 20A breakers. These 1P breakers will feed receptacles in the wiremold. My question is, does the neutral in the 50A feeder ckt count as a CCC? And does a neutral always count as a CCC in a feeder?

 

[iwire]

Situation, 3 phase 50A 4W ckt from panel to feed wiremold 3000 series that has circuit breaker housing that will have (3) 1P 20A breakers. These 1P breakers will feed receptacles in the wiremold. My question is, does the neutral in the 50A feeder ckt count as a CCC? And does a neutral always count as a CCC in a feeder?

It depends if the major portion of the load is non-linear or not.

 

[chris kennedy]

And does a neutral always count as a CCC in a feeder?

Also 310.15(B)(4) says 'same circuit', no mention of branch circuits or feeders.

 

[chevyx92]

It depends if the major portion of the load is non-linear or not.

I dont know for certain. I'm assuming it probably is because they will be using these wiremold recepts to test electronic equipment. What it means to me, is I either run 3/4 EMT with (4) #8thhn plus #10 ground {if the neutral is not a CCC} or run 1" EMT with (4) #6thhn plus #10 ground{if the neutral is a CCC}.

 

[richxtlc]

It would be considered a CCC because of the single phase loads. You could not guarantee that the load will always be balanced and therefore no neutral load. The neutral would not be considered a CCC if all the loads were three-phase.

 

[iwire]

It would be considered a CCC because of the single phase loads. You could not guarantee that the load will always be balanced and therefore no neutral load.

That is incorrect, please check out 310.15(B)(4)(a).

The fact the the neutral conductor actually does carry current is not a factor in determining if the neutral conductor is considered a 'current carrying conductor' for the application of derating.

 

[augie47]

It would be considered a CCC because of the single phase loads. You could not guarantee that the load will always be balanced and therefore no neutral load. The neutral would not be considered a CCC if all the loads were three-phase.

Why? Assume for a moment, the load was all 120v incadescent lighting.
If all phases were equally loaded what would your neutral current be ?

 

[chris kennedy]

It would be considered a CCC because of the single phase loads. You could not guarantee that the load will always be balanced and therefore no neutral load. .

Where do you see that?

310.15(4) Neutral Conductor.

(a) A neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to be counted when applying the provisions of 310.15(B)(2)(a).

 

[cadpoint]

I dont know for certain. I'm assuming it probably is because they will be using these wiremold recepts to test electronic equipment. ....

I don't think I'd share a neurtal for the this type of equipment, and your doubling down with all this equipment to be on a 3 pole breaker.

 

[iwire]

I don't think I'd share a neurtal for the this type of equipment, and your doubling down with all this equipment to be on a 3 pole breaker.

He is running a feeder, going to be tough not to share a neutral.

 

[chevyx92]

He is running a feeder, going to be tough not to share a neutral.

Would you say the neutral counts as a CCC based on the fact that there will be electronic equipment plugged in for testing? This is really all I know of that will be plugged in.

 

[cadpoint]

I missed it..., and he even stated it correctly twice...
Locked in the same bad thought!

Thrown a life bouy, Shoot a flair, I've been shot down... Gads :roll:

 

[iwire]

It sounds like per the NEC you should.

 

[winnie]

Why a 50A feeder going to what is at most a 20A load?

-Jon

 

[jumper]

Why a 50A feeder going to what is at most a 20A load?

-Jon

Good point.

From OP:
Situation, 3 phase 50A 4W ckt from panel to feed wiremold 3000 series that has circuit breaker housing that will have (3) 1P 20A breakers.

 

[hurk27]

I would think that the total wattage passing through the 4 conductors would always equal the max amount of wattage that can pass through any three of the conductors if balanced, so at any amount of balance or not would create the same amount of heat build up in the conductors as if there were only 3 hots ran that had a balanced load.

So my vote is no count for the neutral, if the electronic loads don't pose non-linear currents or harmonics.

 

[richxtlc]

If the load is balanced and will remain balanced then there is not need to count the neutral as a CCC, but how can you assume a balanced load when you have 3 individual plug circuits that can be used by one, two or three circuits at any given time. If it were just a 3-phase load, I would not count the neutral as a CCC.

 

[chris kennedy]

If the load is balanced and will remain balanced then there is not need to count the neutral as a CCC, but how can you assume a balanced load when you have 3 individual plug circuits that can be used by one, two or three circuits at any given time.

You are correct in theory, the grounded conductor is bound to carry current almost all the time. Read 310.15(B)(4)(a) again. We don't have to count it.

 

[iwire]

If the load is balanced and will remain balanced then there is not need to count the neutral as a CCC, but how can you assume a balanced load when you have 3 individual plug circuits that can be used by one, two or three circuits at any given time. If it were just a 3-phase load, I would not count the neutral as a CCC.

Please read the NEC section given, even though the conductor will carry current the NEC allows us to ignore it for the purposes of derating.

 

[roger]

If the load is balanced and will remain balanced then there is not need to count the neutral as a CCC, but how can you assume a balanced load when you have 3 individual plug circuits that can be used by one, two or three circuits at any given time. If it were just a 3-phase load, I would not count the neutral as a CCC.

Rich, consider this example of linear loads.

In a perfectly balanced wye 20 amp MWBC loaded 100 percent there will be a total of 60 amps flowing in the circuit, 20 amps flowing in A, B, and C phases, the neutral has 0 amps flowing.

Turn off any one phase and the neutral will carry the same as the other two phases for a total of 60 amps, no change.

Mix any odd number into the equation with any or all of the three phases and the circuit will still only have a total of 60 amps flowing, no change again.

There is no reason in most situations to have to count a neutral as a CCC.

Roger