Old work electrical box in baseboard

[Wayne Whitney]

Hi,

In addition to the usual ears, my old work box (Carlon B120R) has 4 tabs projecting out of the corners, with holes in them. Are these tabs for screwing the box directly to a solid wall surface (e.g. a baseboard)? The manufacturer's website doesn't mention this installation method, so I thought I'd double check here.

Thanks, Wayne

[Nehmo Sergheyev]

- Wayne Whitney -

- Nehmo - Carlon B120R pic:

The ears on the screws go inside the wall and clamp the wall material between the ears and the tabs. Explained: If the wall material is something more solid than sheet rock, sure, you can put screws in the holes in the tabs to mount the box. Often in construction, you have to make-do in a given situation. Many things can be mounted in several different ways. A box with an accurate box hole in solid baseboard with screwed-in tabs will make a more solid mounding than one with the ears-behind-sheetrock method. But usually the baseboard level is not where a box is positioned.

The best method is to figure out where the stud is and mount to that like with a new-work box.

Usually people don't install old-work boxes correctly and they end up being loose.

[Wayne Whitney]

OK, great, that's easier for my application, and as you say, stronger too.

My baseboards are 1x10s, so it works out OK, the boxes are maybe 3" above the finish floor. Anyway, a previous owner already made the choice of locating the boxes for me; I'm just updating the circuits.

Cheers, Wayne

[HorneTD]

Wayne Make sure that your boxes are large enough for the number of wires, devices, and interior clamps that they will have to contain. As an example a 3" X 2" device box that has a receptacle served by a twelve gage, twenty ampere, circuit with the cable held by internal clamps and Equipment Grounding Conductors in the box would need to be three and one half inches deep to have the requisite number of cubic inches capacity.

-- Tom H

[Wayne Whitney]

Yes, this is always good advice. One advantage of the fact that my receptacle boxes are mounted in the baseboard is that I can fit a 3.5" deep box in my 2x3 walls (1908 house). I had a heck of a time getting a big enough double gang switch box for a light and (separate) ceiling fan control in a 2x3 wall, since I could only use a 3" deep box. 7 conductors, EGC and 2 yokes makes 12 allowances, which is 27 in^3 for

12 gauage wires. Most shallow PVC boxes are 25 in^3, I had to track down a fiberglass box from Allied Moulded that is 28 in^3.

Even with the 3.5" deep boxes, it seems hard to stuff the wires into a single gang box, since it is difficult to push the EGCs all the way into the very back, as the box is not that wide and the device is somewhat in the way at this point. Is there any secret to this?

My understanding is that the volume stamped on a non-metallic box already takes into account any clamps built into the box and that no allowances are required. The clamping allowances would apply when dealing with a metal box of standard sizes, with the internal clamps at the back of the box, since these boxes are available with and without internal clamps. Is this correct?

Cheers, Wayne