I?m looking at a school project that requires breaker panel replacement. The specs call for all circuits to be replaced with new wire to the first utilization device. My problem is the existing circuits all use shared neutrals 3 hots and a neutral. The new requirements call for dedicated neutrals to the first utilization device. Is there a problem tying all the neutrals together after the first device for each phase conductor? It would seem at some time you may me tying one or two maybe three new neutrals to a single sheared neutral? I also understand pipe will have to be added to accommodate the new fill. Please post your thoughts or comments I have not run into this type of request it seems senseless.
sheared neutral replaced w/dedicated?help!
- Thread starter scottay
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Since they are all full size there would be no "ampacity" problem, but you would technically be in violation of 300.3(B)(1).
As you say, the requirement is useless.
I would approach the engineer/inspector with the fact thats it a violation and see if you could not get an agreement to go back to a shared neutral from the panel, keeping in mind the requirements of 210.4
As you say, the requirement is useless.
I would approach the engineer/inspector with the fact thats it a violation and see if you could not get an agreement to go back to a shared neutral from the panel, keeping in mind the requirements of 210.4
- Location
- New Jersey
- Occupation
- Journeyman Electrician
You cannot splice all of the new individual neutrals together. That would create parallel conductors which must be a minimum of #1/0. Whoever wrote this specification didn't really do their homework.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Scott, welocme to the forum! 
Draw a typical MWBC, say as a string of outlets using A-B-C-A-B-C, etc. Now, re-draw it with separate neutrals for each phase.
As you will see, there's nothing to be gained by running any redundant conductors to only the first device, as suggested above.
This will likely be impossible unless you open and pull new grounded conductors to every box except the last one on each phase.
Draw a typical MWBC, say as a string of outlets using A-B-C-A-B-C, etc. Now, re-draw it with separate neutrals for each phase.
As you will see, there's nothing to be gained by running any redundant conductors to only the first device, as suggested above.
mtnelect
HVAC & Electrical Contractor
- Location
- Southern California
- Occupation
- Contractor, C10 & C20 - Semi Retired
Get it straight ... Once and for all !!!
Get it straight ... Once and for all !!!
With the "AFCI" & "GFI" which all have a seperate connection for the neutral ... They all must have "DEDICATED NEUTRALS" ... All neutrals must be identified at every junction box ... DO NOT CROSS NEUTRALS ... This is were the all the prblems occure ... Also known as "Phantom Tripping" ...
Michael E. Olson
Get it straight ... Once and for all !!!
With the "AFCI" & "GFI" which all have a seperate connection for the neutral ... They all must have "DEDICATED NEUTRALS" ... All neutrals must be identified at every junction box ... DO NOT CROSS NEUTRALS ... This is were the all the prblems occure ... Also known as "Phantom Tripping" ...
Michael E. Olson
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- Location
- Massachusetts
This is a project at a school there should not be any AFCIs and I doubt that there are GFCI breakers.
Can you point to that requirement in the NEC?
mtnelect
HVAC & Electrical Contractor
- Location
- Southern California
- Occupation
- Contractor, C10 & C20 - Semi Retired
"afci" & "gfci" - "phantom tripping"
"afci" & "gfci" - "phantom tripping"
Thank you for your interest in my reply.
When "GFCI's" first came out we had alot of service calls on "Phantom Tripping". We spent many lost hours and days on trouble shooting this problem.
Both types of "GFCI's" & "AFCI's" breakers monitor both the hot and the neutral, what goes out must match what returns, if not then there is a "Ground Fault".
The most common problem was on "MWBC's", where the neutral is shared by both hots.
Example: Multi Wire Branch Circuit (MWBC)
a. One circuit feeds a "GFCI" Feed Through Receptacle in the first bathroom, sharing the common neutral in the other bathrooms.
b. One circuit feeds lighting in the hallways, sharing the common neutral from the Feed Through Receptacle in the bathrooms.
c. An appliance is pluged into the "GFCI" Feed Through Receptacle in one of the other batthrooms.
d. The hallway light is turned on.
e. The "GFCI" Feed Through Receptacle in the bathroom senses an additional load from the hallway light and "Trips".
From that point on we always identified all "GFCI" & "AFCI" neutrals in every junction box, from other circuit neutrals.
Then we took it a step further, all neutrals are identified in every junction box.
It would not surprise me, that sometime in the future this will be a code requirement.
Mountain Electric Company
Michael E. Olson - Owner
Since 1976
"afci" & "gfci" - "phantom tripping"
Thank you for your interest in my reply.
When "GFCI's" first came out we had alot of service calls on "Phantom Tripping". We spent many lost hours and days on trouble shooting this problem.
Both types of "GFCI's" & "AFCI's" breakers monitor both the hot and the neutral, what goes out must match what returns, if not then there is a "Ground Fault".
The most common problem was on "MWBC's", where the neutral is shared by both hots.
Example: Multi Wire Branch Circuit (MWBC)
a. One circuit feeds a "GFCI" Feed Through Receptacle in the first bathroom, sharing the common neutral in the other bathrooms.
b. One circuit feeds lighting in the hallways, sharing the common neutral from the Feed Through Receptacle in the bathrooms.
c. An appliance is pluged into the "GFCI" Feed Through Receptacle in one of the other batthrooms.
d. The hallway light is turned on.
e. The "GFCI" Feed Through Receptacle in the bathroom senses an additional load from the hallway light and "Trips".
From that point on we always identified all "GFCI" & "AFCI" neutrals in every junction box, from other circuit neutrals.
Then we took it a step further, all neutrals are identified in every junction box.
It would not surprise me, that sometime in the future this will be a code requirement.
Mountain Electric Company
Michael E. Olson - Owner
Since 1976
- Status