#10 Neutral

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Two questions.
1. If bid docs said shared neutral must be #10 and you were running MC cable for branch how would you handle(wiring method) that when installing? Don't think they make MC with #12 hots and #10 neutral?
2. Why would they ask for #10 neutral?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Yes they make "super neutral" MC cable with an oversized neutral. Oversized neutrals are for harmonics. Are you actually using shared neutrals?
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
IMHO the use of an oversized neutral is an un-needed response to additive harmonic currents from switching power supplies.

Additive harmonics are a real thing, but power factor correction circuitry in modern switching power supplies mitigates the issue.

'Super neutral MC' is out there. I've never used it, don't know what the price premium, lead time, or minimum quantity is.


Jon
 

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Yes they make "super neutral" MC cable with an oversized neutral. Oversized neutrals are for harmonics. Are you actually using shared neutrals?
We'll they have a note saying " common neutrals should be #10" so to me shared neutrals(MWBC) are allowed. Guess handle ties will have to be used.
 

kwired

Electron manager
Location
NE Nebraska
We'll they have a note saying " common neutrals should be #10" so to me shared neutrals(MWBC) are allowed. Guess handle ties will have to be used.
Are they requiring common neutrals or simply saying they are allowed but need to be 10 AWG if used? Seems if you don't use common neutrals you can ignore this.
 

kwired

Electron manager
Location
NE Nebraska
Not requiring it just mentioning if you use MWBC. So I guess I should figure separate neutrals?
If that makes it more feasible for you yes.
Why. COst more?
MWBC's probably cost less most the time unless they are really short runs. But along with them comes shutting off the other ungrounded conductors when you only intend to work on one of the "sub circuits" or having to shut off the other "sub circuits" to reset a tripped breaker when handle ties are used. Using a common trip breaker instead of handle ties takes down all the ungrounded conductors when only one "sub circuit" had the trip condition. All those things can make for less convenience for the end user and is also a consideration in choosing whether or not to use MWBC's.
 

kwired

Electron manager
Location
NE Nebraska
It's just easier to use 2-wire MC cable than to have to deal with special order MC cable and handle ties.
I don't know about now since prices of nearly everyting has gone up but several years ago I figured two single pole QO breakers and a handle tie cost about the same as a 2 pole breaker. Independent trip was what you gained, though you were still going to have to turn them both off to reset the tripped one. If you ran three phase MWBC's it definitely cost less in materials to use three QO single pole and a three pole handle tie than to use one three pole breaker back then anyway.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
If there is a good distance to run several circuits along the same pathway, it may be better to run a conduit carrying those circuits, or even a feeder to a sub-panel, in a central distribution point.
 
Two questions.
1. If bid docs said shared neutral must be #10 and you were running MC cable for branch how would you handle(wiring method) that when installing? Don't think they make MC with #12 hots and #10 neutral?
2. Why would they ask for #10 neutral?
Typically I run EMT with MWBC's out of the panel to a point closer to the outlets and then transition to MC. In that case just 12/2 MC is typically used. Yes if you run MC all the way home you would need to meet that requirement for a #10 neuter.

A few comments on the handle ties. Note that you only need handle ties and NOT common trip for MWBC's. Three pole common trips are a lot more expensive than 3 single poles and a handle tie. The problem is some brands do not offer a three pole handle tie. When I use handle ties a don't install the center rod so someone can pull off the tie easily if needed to operate a single handle .
 

lordofthisworld

Senior Member
Location
Massachusetts
Two questions.
1. If bid docs said shared neutral must be #10 and you were running MC cable for branch how would you handle(wiring method) that when installing? Don't think they make MC with #12 hots and #10 neutral?
2. Why would they ask for #10 neutral?
They make super neutral MC with #12 hots and #10 neutral. These are mostly used for furniture partitions
 
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