Will NEC allow this?

[ProperPatty]

Anything in the NEC that would stop me from running 2 lines (each from different services) through the same junction box?

[zxcvbob]

Different *services*, or different *circuits* on the same service? It is very unusual to have more than one service to a building.

When I replaced my old 60A service with new breaker box, I gutted the old service box and used it as a big junction box with 7 or 8 circuits spliced into the old wires. The new service box and the old box were connected together with a short piece of RMC. The inspector said it looked good.

That was 10 years ago, so maybe the rules have changed (but I doubt it.) My code book is 1993, so not much point in me looking it up.

Make sure your junction box has enough cubic inches for the number of conductors.

Regards, Bob

[ProperPatty]

Different meter/service..

[zxcvbob]

I can't find a specific restriction, but I think you'll have trouble getting past the rule about only one service per building (with exceptions), and if you have an exceptional case that allows multiple services they must be clearly marked.

Are you talking about a duplex apartment that has 2 meters in a single enclosure with separate disconnects? I *believe* that counts as one service entrance.

Best regards, Bob

[ProperPatty]

Ok, 1 set of wires running down a pipe into a large box, out to two different meters into two seperate panels.

Now, can a line from each panel/disconnect run through the same junction box?

[Steve Smith]

I would assume that these are for two separate apartments? (or one house and a basement apartment?). If that's the case then wiring from two different "dwelling units" can not meet in the same box. I forget which rule this was but I do recall the inspector faulting it in an apartment I once lived in during a general inspection.

Also, you can't link neutrals or grounds between two services: It would be pretty hard to keep bare grounds from touching each other inside a box. For the cost of an extra junction box why go to all the trouble?

[Chris Lewis]

According to ProperPatty :

In Canada, you can't even run two circuits from the same service through a single box _unless_ there's a mechanical separation between the two and/or common disconnect. Ie: our main panels have two sections, one for the main disconnect/breaker, the other for the branches. Two services would be a no-no.

There's something in both codes about a service line feeding up to 6 separate "things" (panels, individual circuits etc) without needing a common disconnect (would imply common junction box of some sort). But downstream of other disconnects, I don't think so.

Ask the inspector.

[Pavel314]

The only thing I'd worry about is that someday someone may flip the breaker on one line, think that he's cut all power to that box and get zapped by the live line. That happened to me when working in an older building; fortunately, I thought to check for power when I unwrapped the second line.

Paul