neutral doesn't count as current carrying ?

[busman]

Yup, as stated at the top of the list.

Here is a more complete list:

In a single phase center tap system:
1 hot + 1 neutral + 1 EGC counts as 2 CCC
2 hot + 1 neutral + 1 EGC counts as 2 CCC (presuming proper selection of hots from different legs)
2 hot + 1 EGC counts as 2 CCC
2 hot + 2 neutral + 1 EGC counts as 4 CCC (separate neutral install)

In a three phase wye system
1 hot + 1 neutral + 1 EGC counts as 2 CCC
2 hot + 1 neutral + 1 EGC counts as 3 CCC (presuming proper selection of hots from different legs)
2 hot + 0 neutral + 1 EGC counts as 2 CCC
3 hot + 1 neutral + 1 EGC counts as 3 CCC (presuming proper selection of hots from different legs)
3 hot + 0 neutral + 1 EGC counts as 3 CCC
3 hot + 2 neutral + 1 EGC counts as 5 CCC (partial separate neutral install )
3 hot + 3 neutral + 1 EGC counts as 6 CCC (presuming proper selection of hots from different legs)

In a three phase corner grounded delta system
1 hot + 1 grounded conductor + 1 EGC counts as 2 CCC
2 hot + 0 grounded conductor + 1 EGC counts as 2 CCC
2 hot + 1 grounded conductor + 1 EGC counts as 3 CCC

The three phase high leg delta system is left as an exercise for the reader

-Jon

Maybe I'm slow today, but it seems that 2 hots + 1 grounded on a three phase corner grounded delta system should be 3 ccc, the same as an ungrounded delta. I don't see how grounding one phase changes the currents.

 

[LarryFine]

Maybe I'm slow today, but it seems that 2 hots + 1 grounded on a three phase corner grounded delta system should be 3 ccc, the same as an ungrounded delta. I don't see how grounding one phase changes the currents.

I concur.

 

[winnie]

Maybe I'm slow today, but it seems that 2 hots + 1 grounded on a three phase corner grounded delta system should be 3 ccc, the same as an ungrounded delta. I don't see how grounding one phase changes the currents.

You are correct. I was thinking 3 but wrote 2. I'd request that a mod edit the count since I got it wrong. *blush*

Jon

 

[infinity]

Fixed.

 

[busman]

Fixed.

Thanks. Can you also fix it in Jon's original post?

 

[qcroanoke]

You count neutrals as current carrying when you have one hot and one neutral or two out of three 3 phase hots and a neutral. You do not count it when the neutral is part of a full MWBC and carries only the unbalanced current from the hot conductors.

The rationale is that whenever there is neutral current, one or more of the phase currents has been reduced in proportion, leaving the heat dissipation the same.

Or. Because the code says so... .

 

[roger]

Thanks. Can you also fix it in Jon's original post?

Done