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#78444 - 09/25/0105:45 PMOne Neutral For Multiple Circuits
I will be running three new circuits to a kitchen. Two will serve two double duplex above countertopo outlets each with a GFCI outlet, and the third will be to a simplex outlet to power just the refrigerator. Can I safely and properly run one neutral for these three circuits?
I will also be running a new circuit to the bathroom with one GFCI duplex outlet on it. Can I safely and properly use that same neutral above? =TB=
#78445 - 09/25/0106:10 PMRe: One Neutral For Multiple Circuits
>Can I safely and properly run one neutral for these three circuits? No way! A "neutral" is a current-carrying grounded conductor.
>Can I safely and properly use that same neutral above? No. And frankly, this question shows that you know enough to be very dangerous. I strongly caution you against doing whatever you have planned... especially as it pertains to taking senseless shortcuts.
You have scared me.
#78446 - 09/25/0107:03 PMRe: One Neutral For Multiple Circuits
The reason everyone is so upset is because the common neutral conductor will be overloaded, and that's not good!
Running the circuits as you have described them will result in as much as 40 amps flowing in the common neutral during peak usage. If they were all on the same Line [AKA "Phase"], that would result in as much as 80 amp load on the common neutral during peak use. That would fry a #12 cu conductor, which is good for only about 30 amps max [fused or breaker size is 20 amps max in most conditions].
What you should do in your case is to run a 3 wire circuit for the Kitchen appliance circuits, place the "Hots" on opposite "Phases" [so that if you checked the voltage between the two hots, there will be 240 volts]. If you do not read 240 volts across the two hots, or if you read no voltage, chances are they are not on opposite lines. Using a two pole circuit breaker could assist in this goal [full space 2 pole units, not just simply a "Stacked" 1 pole breaker]. The type of panel used will determine the exact arrangement. If this is not possible, use two separate 12-2 NM cables - one per 4 plex receptacle / circuit.
For the other two circuits [the refrigerator and the bathroom circuits], use separate 2 wire runs for those circuits. One 12-2 NM cable for the refrigerator circuit, one 12-2 NM cable for the bathroom circuit.
As with the others, I also suggest that you seek the assistance of a Qualified Electrical Installer for this installation. The results of wiring the installation the way you first planned would easily result in a fire!!! This is not an insult, rather it's a very helpful and serious suggestion!
Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!
#78449 - 09/26/0106:40 AMRe: One Neutral For Multiple Circuits
Mr. Brooklyn, I don't recommend your doing what I suggest here, I'm just throwing it in to see the other guy's thoughts, as I've wondered. I haven't and wouldn't do this myself.
What if the run was in conduit, properly phased, and had a #8 neut? (Is that compliant?)
#78452 - 09/26/0108:49 AMRe: One Neutral For Multiple Circuits
Hi Guys: Thanks for the concerned replies. I see that I raised some eyebrows to say the least on this one; it looks like I better re-read my Wiring 1-2-3 book. I'll do as Scott35 said using a 2 pole breaker on the two kitchen circuit and use seperate 12-2s on the two others. I would be using the common type of BX, I'm not sure what NM-B is. My house is from 1907 and I generally, but not in all cases, have been replacing the old cloth covered wire cable as I renovate from room to room.
#78453 - 09/26/0110:04 AMRe: One Neutral For Multiple Circuits
I'm not sure what your NEC says about it, but in the U.K. our "code" specifies that each individual branch circuit leaving a distribution panel must have its own neutral. One large neutral to two or three branches might be OK from the ampacity point of view, but if someone shut off one breaker to work on an outlet they could unwittingly break into a neutral - believed dead - which is still carrying current on the other circuits. Not good.
Joe: NM is Romex, right? What exactly is the difference between NM and NM-B?
[This message has been edited by pauluk (edited 09-26-2001).]