Dear Mr. Electrician: How do I add a dimmer switch and new ceiling light fixture? I want to hang a light fixture where there is currently no wiring.
Answer: When considering to add a dimmer switch and new ceiling light fixture the structure of the building must be considered. NOTE: Some text links below go to applicable products on Amazon. As an Amazon Associate I earn from qualifying purchases.
The methods used to achieve this type of installation will vary according to your building structure and the location of the switches and light fixtures. Below are photos of a simple dimmer and ceiling light fixture installation in a two story condominium.
ADD DIMMER SWITCH AND NEW CEILING LIGHT FIXTURE
You need to determine where you will be getting power from and where do you want the wall switch to be located. In the example on this page I was lucky to find power in an existing wall switch where the client wanted the additional switch located.
Not all wall switches have a hot (LINE) and a neutral. Some just have a hot and a switch leg which cannot be used to provide power to something else.
I used a long thin screwdriver inserted along side of the switch box to feel for any obstacles such as pipes or wood studs. A short piece of fish tape can also be used for probing into a wall.
I removed the existing one gang plastic switch box and cut a hole for a new two gang plastic old work switch box.
The existing black switch leg wire was temporarily identified with green electrical tape. The other black wires get spliced together. The wood stud on the left side of this wall opening is perfect for attaching the new two gang plastic old work electrical box for additional support.
NEW WIRING FOR NEW LIGHT
The access hole in the wall and the access hole in the ceiling were made using “The Grabowski Method” (Hold the Saw at a 45 degree angle) to facilitate the installation of a new wire to feed the new light fixture.
I had to drill inside the wall to avoid damaging the crown molding around the ceiling. A large hole was needed to fit the Milwaukee right angle drill into the wall to drill up into the top support plate.
I did have to cut holes in the ceiling and the wall to facilitate the installation of a new 14/2 Romex cable to the new light fixture location. I cut the holes at a 45 degree angle inward to make it easy for patching later.
This hole was made using “The Grabowski Method” of cutting holes in drywall. The compass saw is held at a forty five degree angle inward when cutting, to give a beveled edge to the cut out piece of drywall. This makes it much easier to patch the hole using the same piece of cut out drywall and some joint compound. Lately I have been using my Milwaukee Cordless Multi-Oscillating Tool to cut such holes.
The above view is the inside of the wall through the hole in the previous photo. The big hole in the wall was needed to accommodate the big angle drill and a long auger drill bit.
I had to drill a hole using my angle drill to penetrate the top supporting plate in the wall to get the new Romex cable into the ceiling.
After the new Romex cable was installed up to the ceiling, I caulked the hole through the wood top plate with a fire rated caulk. This is done to prevent the flow of air which would help support a fire.
The hole above is for the new octagonal electrical box that will support the light fixture where the customer wanted it. The existing cables in the ceiling are set back far enough to provide clearance for the new box. You can see the side of the laminated beam on the bottom edge of the hole.
Before cutting any holes in the ceiling or walls to install electrical boxes, recessed lighting, or something, probe with something long and thin. After I measure and mark where I want my hole to be I will use my awl or a long thin screwdriver to make a tiny hole (1/4″) in the drywall.
I push the long screwdriver into the wall or ceiling in all directions. Then I do the same thing with a short piece of fish tape. On ceilings I will also use a piece of metal coat hanger bent in an L shape to feel for things close to the ceiling surface such as resilient channel.
Click here to read my blog post about fishing wires in walls and ceilings.
Because this ceiling was supported by trusses instead of solid wood joists I was able to get my fish tape through very easily after the holes were made.
I have several pieces of short fish tape which had broken off of my longer fish tapes. The short fish tapes come in handy for small jobs like this. See my post about wire pulling in walls for more information.
Sometimes it is easier to work with two or more short fish tapes than one long one.
When I cut open the ceiling to fish the wire in the above photo, I was delighted to see that a hole in the laminated beam was already drilled.
The fender washer allows for a little adjustment to get the box positioned correctly. The other screws lock it in place. Note the copper ground wire attached with a 10/32 screw. I had originally planned to install an adjustable retrofit fan brace and box, but the joists were too close together to fit it in.
In most cases I would have used a fan rated ceiling box and installed a 14/3 cable for future fan use. However this light fixture installation was in a small nook next to the dining room. It was not likely that a ceiling fan would ever be wanted there.
HANGING A NEW CEILING LIGHT FIXTURE
Everything metal must be grounded. Because I used a metal box and grounded it, the round fixture mounting bracket is grounded by being physically attached to the ceiling box. If the ceiling box was plastic it would have been necessary to install a ground wire onto the green screw on the mounting bracket. The light fixture ground wire will connect to the ground wire in the ceiling electrical box.
My blog post about how to ground outlets and switches might be useful to you.