I am updating some outdoor flood lights. See pics below. The old unit has a square base, the new unit has round and a round rubber gasket. Here is a link to the new LED unit.

Amazon.com: Lithonia LED Outdoor Security Floodlight with Dusk to Dawn Light Sensor, Motion Activated Perimeter Protection, White: Patio, Lawn & Garden



I have a sawzall as well as an oscillating multi tool, so cutting a hole to accomodate a round box is no problem. I believe i just remove the collar around the conduit and remove the old box and then install the new.

My question is about the type of box i should use. I am partial to the plastic Carlon boxes because they are easy to work with but I want do do the best installation (not sure if this would be properly grounded). I can certainly get metal if that's better.

Thoughts?

Please be specific if you recommend a type of box so I can be sure to get the right thing.

BTW I also have an elastomeric caulk for sealing the perimeter as well.

Thanks!

 

You don't have conduit as your feed.....you have 14-3 BX. (metal clad)
Therefore you'll need to use a metal box.

Normally you could change the mounting plate on the new light fixture to match the existing box but the box is oriented in the wrong direction and those three units would be cramped.

You'll need a 4" octagon box for old work. In the link below is just what the doctor ordered.

2-1/8 octagon old work box

Here's a video of the same octagon old work box

 

Thank you. That looks like a great solution, the only problem is my light housing is 112mm in diameter, and those old work tabs are 120mm from end to end. Is there no way around this since this is old work, and I need an octagonal/round box for my gasket to seal? Perhaps I just have to paint the metal tabs and screws sticking out? Or perhaps there is a decorative ring for the base of the fixture?

 

Technically that light fixture is setup for a 4" round weatherproof box. Those boxes are surface mount and won't work for you.

They make a perfect box that would have worked for you but it's made of plastic. It's a 4" round box like the metal box but it has a complete flange around it.

In your case you're going to have to improvise. Paint the mounting tabs. I don't know of any trim ring that would work there.