How can we move a subpanel without replacing the supply cable?

Question

We recently installed a subpanel, installed it ourselves and had it inspected. Now, as part of the ongoing renovation of the house, we have decided we need to move the panel over 22 inches. The 6 awg cable won't reach that far (why O why did we not build in some slack?). The cable comes up from the basement into the attic floor then across the floor about 10 ft then down into the subpanel, which has its highest switch at 5ft above floor.

So far the ideas we have are:

1. Build a bulkhead so the cable can go diagonally across that space, which gives us some - not much - slack.
2. Raise the subpanel so that the highest switch is 6ft 7" above floor (which I think is code max) - altho I think we'd still be short 5".
3. Pull new 6 awg. This is feasible because the drywall it runs behind is not yet finished.

Any recommendations, ideas? Thx

Answer 1

This is pretty routine, and I've done a lot of it.

Slap a 120mm (4-11/16 if you really want to say all that) square deep junction box where the subpanel used to be. Plumb 3/4" preferably 1" EMT or rigid conduit from the new subpanel to the aforementioned box. (Do all this in reverse; coordinate the location of subpanel and junction box so the conduit run is easy, then run the conduit.)

Bring the #6 cable into the 120mm box with a cable clamp. Attach the cable ground wire to the junction box shell. The metal conduit is the ground path, and you don't need to run a ground wire unless you really want to.

Get some #6 stranded THWN-2 wire. Run three wires:

• neutral (must be white or gray wire)
• L1 (any color but green)
• L2 (any color but green, bonus style points if different color than L1)

If L1 or L2 are white or gray, you must mark them near both ends with a color of paint or tape other than white, gray or green.

These wires run from the junction box to the subpanel lug. Inside the junction box they are wire-nutted or spliced to the corresponding wire in the cable.

If you want to splice other cables into that box too, use 1" conduit and don't go crazy - no more than four circuits per conduit, and watch your junction box fill cubic inches, on a deep 120 you're nearly out already. They do make box extensions.