nec grounding rules

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jemezwired

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Hello everyone,
We are working on a project replacing old subpanels in several apartment buildings. A feeder circuit is brought from the main service to feed four panels per circuit, with the feeders being tapped using the 10' rule. I have been trying to find out if it is allowable to use the neutral bar in the subpanels as a splice point for the neutrals feeding the other panels or if it has to have a solid nuetral all the way to the last panel with taps coming directly off of an "unbroken" neutral?
 
Re: nec grounding rules

I believe if you did as described, your neutral would be undersized as the one conductor is serving 4 sets of feeders. I have to look for a code section.
 
Re: nec grounding rules

The four subpanels are protected by a 2-pole 100Amp breaker at the main service. The panels are MLO with the neutral sized to the 100 Amp circuit. I'm just trying to figure out if it is allowable to take the neutral to the first panel's neutral busbar and then continue it to the other 3 panels from there or if it needs to be a continuous length to the last panel with "taps" coming off of it along the way?
 
Re: nec grounding rules

The neutral has to be run with the other conductors of the feeder,it can not be run independently.

frank
 
Re: nec grounding rules

300.3 (B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).
 
Re: nec grounding rules

You cannot use the neutral bar in the panelboard for this application unless the panelboard is equipped with power takeoff lugs for the hot wires. The panelboard would be equipped with field installed power takeoff lugs ( can be done with SquareD ), doulbe main lugs ( General Electric ), or factory installed power takeoff lugs which can be done with any other make.

However, youn will probably find that it is cheaper to use a pull box and gutter taps or split bolts in the pull box. You can get a gutter tap kit from SquareD that has box lugs connected together similar to a power distribution block. You can also go the Shawmut and get power dirtribution blocks.

Just remember that you cannot put 3 wires into a split bolt!
 
Re: nec grounding rules

Many thanks to Bondingjumper, Benaround, Jwelectric, Donresqcapt19, and mc5w... I appreciate the input from fellow professionals!
Just to let you know, the neutral conductors are definitely routed with the phase conductors, no problem there. I was more concerned with the listing of the panel nuetral bar for this application. A question for mc5w though, where did you find the information about this only being allowed in a panel that has extra power take-off lugs?
 
Re: nec grounding rules

See NEC 312.8

The panelboard has to have enough space for this application. In the case of SquareD 100 amp 2 and 3 pole power takeoff lugs the lugs plug in place of a 100 amp circuit breaker. As long as the panel has enough wire bending space for a 100 amp branch breaker, you can use the plug on power takeoff lugs.
 
Re: nec grounding rules

There is no requirement (to my knowledge anyway) that the neutral wire cannot be spliced along the way. I think that is what you are asking, although its not completely clear.

There is only one case that I can recall where an unspliced wire is required, and that is for a GEC.

The only issue I would have with what I think you are planning to do is that if someone has to work on one of the panels down the road, he might well have to shut off power to all 4 of them.
 
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