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-   -   One circuit, two neutrals to bus bar? (http://www.diychatroom.com/f18/one-circuit-two-neutrals-bus-bar-169830/)

tylernt 01-22-2013 02:03 PM

One circuit, two neutrals to bus bar?
 
In my detached shop, I had 12/2 coming off a breaker in the main panel and going directly to all the lights. All the lights are fluorescent, and controlled with pull chains.

Since I don't like to wave around in the dark looking for a pull chain, I added new 12/3 going to a light switch near the panel (which is conveniently near the door). Black runs from the breaker to the switch, then red from the switch goes back into the panel. The red is nutted to the old Romex coming into the panel and going to the lights, so all lights are now controlled with one switch.

It occurs to me that I now have two neutrals (and grounds) on the same breaker -- one from the 12/3 going to the switch, and another from the old Romex feeding the lights. Both feed into the neutral bus bar at different locations.

Is this bad?

I pulled a permit and will be getting it inspected, but I don't want the inspector to think I'm an idiot... just to be clear, I am an idiot, but try to hide it. ;)

P.S. If you're wondering why I ran 12/3 to the switch instead of using a switch loop, it's because there's a second switch there that runs to an exterior light. That exterior light is fed from the switchbox, so it needs a neutral there.

mpoulton 01-22-2013 02:12 PM

Not only is it not bad, it is now required by code. All switch locations now require a neutral, so new switch loops have to be done with 3-conductor cable. This is to accommodate dimmers and occupancy sensors that require a neutral, since some people had been improperly using the grounding conductor instead. I assume the neutral is just wire nutted off in the box? That's fine.

tylernt 01-23-2013 12:00 PM

Thanks. So, no problem with two neutrals from the same circuit landing on the bus bar?

mpoulton 01-23-2013 12:48 PM

No, not in this case.

AllanJ 01-23-2013 07:54 PM

You really should not have two neutrals and one hot coming back to the panel for the same circuit.

When you strung the new cable from the panel, if you connect the new neutral to the panel neutral strip (bus bar) then the hot must be connected to a breaker in that panel (may share with another circuit). Here the hot may not be connected to and fed by a hot in a different cable at a location up in the house.

Put it another way, given any neutral conductor up in the house, there must be exactly one path back to the panel and it must be the same path (same conduit or cable) that the corresponding hot conductor uses.

AllanJ 01-23-2013 08:00 PM

You really should not have two neutrals and one hot coming back to the panel for the same circuit.

When you strung the new cable from the panel, if you connect the new neutral to the panel neutral strip (bus bar) then the hot must be connected to a breaker in that panel (may share with another circuit). Here the hot may not be connected to and fed by a hot at a location up in the house.

Put it another way, given any neutral conductor up in the house, there must be exactly one path back to the panel and it must be the same path (same conduit or cable) that the corresponding hot conductor uses.

tylernt 01-23-2013 09:50 PM

1 Attachment(s)
I've attached a diagram of what I have done. Hot comes off the breaker, then is pigtailed to two switches. One switch switches on the red, which comes back into the panel and then out to the lights. The other switch switches an exterior light.

I don't believe anything becomes a parallel conductor (which I know is a no-no), as one neutral is dedicated to the exterior light and the other neutral is dedicated to the interior lights.

AllanJ, if you still feel that is incorrect, what is the fix? This might be analogous to taking two circuits and double-tapping them into a single breaker. When two circuits are combined in this manner, are the neutrals pigtailed?

tylernt 02-08-2013 01:48 PM

Followup: passed inspection today. Not that that makes it right, of course, but it makes it right enough. ;)

AllanJ 02-08-2013 06:42 PM

Since it passed inspection I would leave it the way it is.

Random musings ...

When two circuits are doubled up with one breaker I consider it preferable to wire nut the two hots to a pigtail which is in turn connected to the breaker screw (required if the screw terminal is not designed with ridges or a cap washer specifically intended to permit two wires under one screw). And wire nut the two matching neutrals to a pigtail which is a single wire end to connect to the neutral bus bar.

But often doubling up of two circuits on one breaker is done at a later date from original installaton and is is common to forget pulling off the two neutrals and connecting them to a single pigtail to reconnect to the neutral bar. Furthermore, if the two circuits are (again)given their own breakers, their neutrals must run separately to the bus bar. All this favors leaving things as is, too

As you have it, you have a "switch loop with continuing feed" (the cable to the right) for the light fed from the bottom. A switch loop with feed (with neutral) is inherently okay and also required for switch loops under the 2011 NEC. In a switch loop neutral goes directly to the light and hot goes to the switch. That is what you have now. We do not install a second neutral coming back from the switch accompanying the switched hot and connected to the light So what you have fits the definition of a switch loop.

In some cities, the panel may not be used as a pass through, as you are doing for the switched hot from the right (switch) to the bottom light). To correct that, you could mount a junction box just outside the panel and reroute the right cable and the bottom cable to the junction box, adding a single cable for power feed from the panel to the junction box. But again, since it passed inspection as you have it, you don't need to worry about it.


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