Sharing Neutrals

Status
Not open for further replies.
Ok so as this relates to estimating. If I have an area of lighting and the engineer shows this area fed by circuit 1 and 2 of the same panel I would not be sharing a neutral for these two circuits, correct?

BTW this leads me to another question. The circuits listed on the drawing are the circuits that MUST be used and wired to that breaker? I would assume so 99% of the time. Unless in my question above there was a spare circuit 3 could you say I'm going to wire circuit 2 to the 3 instead? Why is phase balancing coming to mind and telling me you can't do that. Follow engineers circuit designation/panel schedule!!?? Thanks
 
mstrlucky74 said:
Ok since I started this great dialogue..lol..can someone help me out this be able able to identify a,b and c phases in panels as fletch mentions above. Going down left hand side of panel with beakers 1,3,5,7 etc. starting with circuit 1....is that phase A? Then circuit 3 is phase B then 5 is C then 7 A etc.?

starting on right side of panel would 2 be A and so on? Thanks
Click to expand...

sorry, brainfart last night on the 3ph panel (the second A on the same side would be 9, not 4). iwire's notation is correct. a 3ph breaker would occupy spots 135, or 246, in a 3ph panel. split phase or single phase would have single or double pole breakers only and the layout would be as follows

1 -- A -- 2
3 -- B -- 4
5 -- A -- 6
7 -- B -- 8

and so on. even if the panel is wired with phases AC or CB, they would alternate the same way.

I believe the first spot in a 3ph panel would be A phase as you suggest tho I'm coming up blanks for a code section that says it must be wired that way, only that high legs are B phase. A single phase panel fed from a 3ph may not even have an A phase.
 
JFletcher said:
sorry, brainfart last night on the 3ph panel (the second A on the same side would be 9, not 4). iwire's notation is correct. a 3ph breaker would occupy spots 135, or 246, in a 3ph panel. split phase or single phase would have single or double pole breakers only and the layout would be as follows

1 -- A -- 2
3 -- B -- 4
5 -- A -- 6
7 -- B -- 8

and so on. even if the panel is wired with phases AC or CB, they would alternate the same way.

I believe the first spot in a 3ph panel would be A phase as you suggest tho I'm coming up blanks for a code section that says it must be wired that way, only that high legs are B phase. A single phase panel fed from a 3ph may not even have an A phase.
Click to expand...

:slaphead:

Would be 7, not 9. Need more coffee
 
mstrlucky74 said:
Ok so as this relates to estimating. If I have an area of lighting and the engineer shows this area fed by circuit 1 and 2 of the same panel I would not be sharing a neutral for these two circuits, correct?

BTW this leads me to another question. The circuits listed on the drawing are the circuits that MUST be used and wired to that breaker? I would assume so 99% of the time. Unless in my question above there was a spare circuit 3 could you say I'm going to wire circuit 2 to the 3 instead? Why is phase balancing coming to mind and telling me you can't do that. Follow engineers circuit designation/panel schedule!!?? Thanks
Click to expand...


when it comes to estimating, you have to get a feel for it. No one rule fits all. If you don't have a more experienced estimator in your office to guide you then you just have to make decisions and live with them. On a project with that in the spec, and nothing that tells me I have to limit the number of circuits in a conduit, I would run 4 wires plus ground in a 1/2" conduit to an area, with a junction box, and extend individual circuits from there, period. I wouldn't care how the person actually runs it. You like I had to do, are the type person who has to let go of being too precise. You will never estimate it exactly the way it is built.
 
iwire said:
If a greenhorn is running a job that is more of an issue than the spec



Yes it is too anyone with experience and code knowledge.



Only to those who don't know electrical work.




Because the specs say so and the more the job costs the more money to be made.
Click to expand...

Thanks for validating every point I made. :thumbsup:

JAP>
 
jap said:
Thanks for validating every point I made. :thumbsup:

JAP>
Click to expand...

No it doesn't the original quote says, "on two or three phases" Your whole premise of two wires on the same phase sharing a neutral was a trip down the rabbit hole.
 
Strathead said:
No it doesn't the original quote says, "on two or three phases" Your whole premise of two wires on the same phase sharing a neutral was a trip down the rabbit hole.
Click to expand...

Yes it does but does not clarify which phases.
And I never said you could share a neutral on the same phase.

The spec didn't say you couldn't.

Jap>
 
In previous code cycles, 'common neutral' circuits and feeders were explicitly permitted in some situations, but not explicitly prohibited in other situations, so the discussions of exactly where they were permitted and why one would bother to use such a strange design were long and very convoluted :) They are still permitted for 'outdoor lighting circuits'.

See, for example
http://forums.mikeholt.com/showthread.php?t=170010
http://forums.mikeholt.com/showthread.php?t=120023
http://forums.mikeholt.com/showthread.php?t=84102

-Jon
 
iwire said:
It also does not say we cannot use a tape alone to make a splice but the code does.
Click to expand...

May be,

But since this whole thread was started because of the OP couldn't make sense of the way a sentence in the spec was written, and its obvious why because the way it is written does not say anywhere that this is referring to a MWBC, which all of us know that's probably what there intent was, and we know you don't share a neutral with more than one circuit on the same phase, so, do you follow the spec or what you know is right by the code?

I'd tend to follow what I know is right.

My whole point is that spec is not clear as written no matter how much you want to read into it.

JAP>
 
winnie said:
In previous code cycles, 'common neutral' circuits and feeders were explicitly permitted in some situations, but not explicitly prohibited in other situations, so the discussions of exactly where they were permitted and why one would bother to use such a strange design were long and very convoluted :) They are still permitted for 'outdoor lighting circuits'.

See, for example
http://forums.mikeholt.com/showthread.php?t=170010
http://forums.mikeholt.com/showthread.php?t=120023
http://forums.mikeholt.com/showthread.php?t=84102

-Jon
Click to expand...

They are still permitted for feeders, too.
 
Strathead said:
No it doesn't the original quote says, "on two or three phases" Your whole premise of two wires on the same phase sharing a neutral was a trip down the rabbit hole.
Click to expand...

Be careful not being specific what you meant by that.

I might speculate.

JAP.
 
Status
Not open for further replies.
Top