Share Neutral In Terminal Box

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Electriman

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Question,

Can we take one (1) neutral wire from last over current protection panel and share it for all circuit in the terminal box near the loads? The loads are lightings.
 
Electriman said:
Yes. But does it make a difference?
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Yes. Outside lighting equipment is the only place where you can run a common neutral for branch circuits on the same phase [225.7(B)]... at least under recent Code editions.
 
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Smart $ said:
Yes. Outside lighting equipment is the only place where you can run a common neutral for branch circuits on the same phase [225.7(B)]... at least under recent Code editions.
Click to expand...

Yes, that's what I was thinking too. If he said indoor then nope.
 
Smart $ said:
Yes. Outside lighting equipment is the only place where you can run a common neutral for branch circuits on the same phase [225.7(B)]... at least under recent Code editions.
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OK, so since I have three phase then I need to run three neutral wires to terminal box and then power each lighting fixture with a 3-C cable (Hot-Neutral-Ground). How about ground wire? Do I have to follow the same rule? (One ground wire for the load on each phase)

Thanks
 
Electriman said:
OK, so since I have three phase then I need to run three neutral wires to terminal box and then power each lighting fixture with a 3-C cable (Hot-Neutral-Ground). How about ground wire? Do I have to follow the same rule? (One ground wire for the load on each phase)

Thanks
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How many circuits... and # of circuits for each phase?

With three distinct phases, you can run a MWBC with three hots (A, B, C), one neutral, one EGC to the terminal box. You can distribute from there with 2/C w/G cable.
 
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Smart $ said:
How many circuits... and # of circuits for each phase?

With three distinct phases, you can run a MWBC with three hots (A, B, C), one neutral, one EGC to the terminal box. You can distribute from there with 2/C w/G cable.
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The number of circuits varies. In my current project I have 6, 9, 11, and 14 circuits on different lighting panels. My preference is to use single conductor wire since the field work is easier. The project is industrial lightings. On the other hand I have to place a lighting contactor in between, so long story short I can't use MWBC.

So based on above information I need to run (number of circuit) hot wires 3 neutral wires and (3 or 1) ground wires. Am I right?
 
Just for completeness, check whether the selected lighting is a non linear load. If it is bad enough you will need to oversize the common neutral.
 
Electriman said:
... On the other hand I have to place a lighting contactor in between, so long story short I can't use MWBC...
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Using a lighting contactor does not prevent you from using MWBC's or a common neutral(s).

Using single conductors in a raceway, you only have to run one EGC... sized for the largest breaker.

Also, when using a common neutral, you have to size it for largest net load on any one phase. When using MWBC's, you only have to size it same as each hot. GoldDigger brings the issue of upsizing the neutral on a MWBC with non-linear loads (due to harmonics, triplens)... but I don't believe that is required by Code, and depends on how heavily the circuits are loaded.
 
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