Adding an outlet in the middle of an existing circuit?

[Toller]

I want to put up a new fluorescent fixture in my basement. Right where I would put a box for an outlet, there is a cable for an appropriate circuit.

The circuit was put in pretty sloppily, so I was able to get 4" of slack right where the new box would go. Is that likely to be enough wire to add an outlet? Seems adequate, but I don't want to cut it up and find I needed

5".

If it turns out not to be enough, I would have to either put in a junction box to add some wire, or pull out the last 10' of cable and replace it with an 11' cable. That would be a lot of work since it all passes through floor joists, but it would save a junction box. Is it worth it?

[Jeff Wisnia]

Given that the box you're adding will be 3-1/2 or 4 inches "wide" where you insert it into the run, that 4 inches of slack should let all the wires project about 4 inches into the box.

That should be plenty to let you pigtail on short lengths of wire (including the ground conductor) and connect those to the new outlet's terminals.

HTH,

Jeff

[chocolatemalt]

But below Code, apparently... 300.14 (2005 NEC) requires 6" as the minimum for conductor slack in a box. Do the inspectors tend to enforce this rule, or is it squishy?

On the other hand, I read somewhere that inspectors disapprove of "excessive" junction boxes. That seems strange to me, since extra boxes would in some cases allow other parts of the Code to be met (like in Toller's case) and provide more flexibility for repairs, future expansion, etc.

[Tom Horne, Electrician]

Pull out that last eleven feet. You will need at least a foot of slack to install a code compliant outlet box. I think that avoiding extra J boxes is always a good thing but that is a personal preference.

[RicodJour]

Cut the wire, insert both ends into the junction box, strip romex jacket back inside the box, strip the colored conductor insulation back as usual, twist the wires back together, add three (hot, neutral, ground) 6" lengths of insulated wire (correctly color coded of course) and twist one end of each wire to the corresponding splice, wire nut each connection. You've just installed pigtails that conform to code. Proceed with wiring the fixture as usual.

R

[John Grabowski]

4" of slack will give you 2" of each end inside of a junction box. Pull out the last 10' and run a new 11' or longer cable. The holes in the joists are already drilled. It's not that difficult a job to pull out an old cable and install a new one. You can cut the old one at different intervals to facilitate its removal.

[RicodJour]

4" of slack plus the wire that would be inside the box if there were no slack - approximately another 3"-4" on a ceiling box. Should be more than enough to pigtail off from that. R

[SQLit]

Sounds like I am going to be the only dissenting opinion.

I believe you will find that the slack mentioned will be painfully short when it comes to working with the wires. I can not see it; 2 inches per side is not really a lot to work with. I will concede that you might get another couple of inches for a box depending on what you install. Now your up to maybe 4 inches per side.

Alternate thought. Some lighting fixtures are rated for a junction box, some are not. If you were to install a 4 foot fixture that was rated as a junction box you would not need to install one. Come in on one end and out the other.

[Toller]

Obviously there should be more material than the 4" I have (someone above thought it was 6") to make it easier to work with, but as long as I have nice secure connections, is there a safety reason for the 6"?

Sometimes code has a safety reason that I wouldn't have thought of, but other times it is just convenience like the number of outlets in a room.