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Subject - Subpanel with no neutrals...
jpayne A little background first: I was checking out a job the other day and it was an older home, built in the 70's or so. The home has the origional meter main panel rated at 100amps in place. The owners wanted to upgrade to a new Square D style panel since breakers are cheaper and last longer than what they currently have (zinsco). They had someone come in and put in a 100 amp square d sub panel right next to the origional panel (about 1/2" over from the origional panel). There is a 100 amp double pole breaker in the origional panel that feeds the sub panel.

Now the part I'm wondering about is that only the hot leads from the house loads were extended over to the sub panel. The neutrals were left connected to the neutral bus in the origional panel. The sub panel has a neutral bus which is wired into the origional panels buss but just has nothing hooked to it but is available for future use if more circuits are added.

Is this acceptable practice? I was called to check an outside pool pump that didn't have any power and noticed all this and I have never seen it done before and honestly don't know if it meets code or not. Oh, pool pump was just a tripped GFCI outlet, nothing to do with how the panel was wired.
iwire
quote:
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 (4).


300.3(B)(1) Paralleled Installations.

300.3(B)(2) Grounding and Bonding Conductors.

300.3(B)(3) Nonferrous Wiring Methods.

1 & 2 definitely do not apply and I doubt highly that 3 would apply.

4 is for specialized industrial narrow width panels that include a remotely mounted neutral bar.

quote:
300.3(B)(4) Enclosures. Where an auxiliary gutter runs between a column-width panelboard and a pull box, and the pull box includes neutral terminations, the neutral conductors of circuits supplied from the panelboard shall be permitted to originate in the pull box.


IMO it is a violation.

If all the conductors pass through the same pipe nipple, the feeders and all the branch circuits that have the neutrals left behind it will not cause problems.

If the feeders run through one nipple and all the branch circuits run through a separate nipple it is possible that you will get inductive heating of the enclosures.

For this to show up you would need the conductors to have some good load on them.

This heating would be caused by the same force that makes an amprobe work.
jpayne As far as the same nipple it's not that simple. The origional enclosure is a flush unit mounted inside the wall. The new panel is a surface mount. All the wiring exits the side of the origional panel, goes through non-metalic conduit (inside the wall) and then into the back of the new panel. I believe there were 3 non-metalic conduits total.
iwire The problem of the metal panel enclosure remains.

The wires of the same circuit must pass through the same hole or would need slots cut in the panel enclosure between the separate raceways in order to comply with 300.20(A or (B)

quote:
300.20 Induced Currents in Metal Enclosures or Metal Raceways.

(A) Conductors Grouped Together. Where conductors carrying alternating current are installed in metal enclosures or metal raceways, they shall be arranged so as to avoid heating the surrounding metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together.

(B) Individual Conductors. Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through which the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit.
KSsparky I believe Bob is correct. I would call this a violation of that exact code reference. I once came across a surface mounted panel with two 2" conduits stubbed up to a metal wireway above a lay-in ceiling. All the branch circuits dispersed from the wireway. The problem was that whoever wired it put all the ungrounded conductors in one conduit and all the grounded conductors in the other. The top of the panel was a very dark brown from the inductive heating over time.
Dave Nix Hi Guys,

Wouldn't this apply also?
quote:
210.4 Multiwire Branch Circuits.
(A) General. Branch circuits recognized by this article shall be permitted as multiwire circuits. A multiwire branch circuit shall be permitted to be considered as multiple circuits. All conductors shall originate from the same panelboard.
JimmyDee Yes David I think that would apply as well. Plus all the other problems, it is just bad workmanship all the way.
Jim