What is the best way to move this electrical box a few inches?

Question

I need to move an electrical box up about five inches from where it is to mount a light fixture. The wall is drywall covered in plaster. The original box was nailed to a stud. Originally I was going to patch the old location with drywall and install a new plastic electrical box in the correct location. What I'm running into is the old wiring, which isn't Romex but rather cloth wire run via flexible conduit screwed into the old junction box. It's about one inch too short to make the move.

I can get the original conduit installed into a new "old work" metal box, but it won't stretch to the new location. I understand there are couplers to extend the length of the conduit, but the length I need to extend it by is so short I feel it would make fitting it difficult. My initial thought is to simply rerun the wire from the outlet to the switch with Romex so I can clamp it into a new box and not worry about the conduit, but I'm no expert at this and don't know if there's an easier way.

Thanks for any advice!

EDIT: @ThreePhaseEel pointed out that this may actually be BX wire, not simple flex conduit, which I imagine changes things up.

Answer 1

If you don't object to having a junction box cover below your new light fixture, consider leaving the original box right where it is. Install the new box above it, and connect the two boxes with a short conduit nipple in a pair of knockouts that line up (or if there's a bit more space than shown, use an offset nipple if that helps to line things up.)

Wire as needed, put a plain cover on the original box and the light fixture on the new box.

If going with the conduit extension approach, consider an FMC to EMT transition rather than FMC to rigid - a 90 degree EMT bend would do the job nicely from the new box to where the FMC ends, and in general EMT is a lot cheaper than rigid (or flex) even comparing a 4 inch nipple to having to buy a 10 foot stick (though by the time you put connectors on the ends you are closer to the same price, but you have more than 9 feet of EMT left for your next project...

If you don't have a bender or a friend you can borrow one from, you can find pre-bent EMT sweeps to purchase, though they may cost more than 10 feet of straight EMT.

Answer 2

I know that it is frustrating to work with a wiring method of which you are unfamiliar, and the temptation is to "run home to momma". However, changing wiring methods midstream can open up a lot of complications, and force you to deal with even more unfamiliar things, and can also lead to really bad workmanship due to unexpected situations you don't know and don't have any prototype to model from.

So let's stick to conduit wiring method, and just cheat ourselves the 5".

I gather this uses a common 1/2" knockout?

Get two 1/2" rigid conduit nuts. They're like a nickel. And you'll already have one from the other fitting.

Get a 4" stick of Rigid conduit, pre-threaded (called a "nipple").

Now, get a coupling.

Remove the "nut" from the old fitting. Screw the old fitting onto the coupler. Screw the 4" Rigid nipple into the coupler. Now you have a ~5" extension on the flexible conduit.

Take one conduit nut, and run it down the Rigid thread as far as it will go. Farther the better.

Stick it through the knockout hole in the junction box. Use the other conduit nut to run down the threads. Use a screwdriver and hammer to bap the castellations to tighten it.

Effectively the junction box will be clamped between the two conduit nuts.