Convert Rectangular Electrical Box in Ceiling to Octagon?

Question

I need to do the opposite of what is talked about in this post: Can I convert ceiling mounted octagon box to electrical receptacle?

Specifically, there is a rectangular electrical box in my ceiling that I want to hang a light from. There is currently no outlet, switch, or other equipment hooked up to it - it has a solid cover screwed over the top of it. I am fairly certain that it is simply acting as a junction box for two independent sets of lights that are in the ceiling.

Any advice for how to go about this? Do I just cut out the old box and insert an old-work octagon into it? Conversely, is there a simple way to hang a ceiling light from a rectangular box?

Answer 1

Edit: You said "rectangular" and "receptacle" so you probably have one half this size, not a square box...

There is a simple way to hang a light from a square box. You may have to look around a bit, but there is a mud ring/reducer that goes from square to round (and the round has the screw positions/spacing so a light fixture attachment will fit.)

Image is from Crescent electric supply web site.

I have a couple of these myself. The adapter ring was in stock but not prominently displayed where I bought it, so it took a little hunting. 2-3/4" is the spacing for the inner screws - I think there's also a smaller one (2-23/32") for smaller fixture spacings.