How should I wire ceiling lights on steel ceiling?

[John in OH]

Looking for advice on a ceiling light mounting question ...

I'm contemplating using the Home Depot 4-bulb, 8 ft long, T8 fluorescent ceiling fixtures (probably 12 of them).



These will be surface mounted on a steel ceiling ... ie., the ceiling will be 29 ga. white ceiling liner panels with major ribs on 9 in centers. This is essentially the same type of panel typically used on barn roofs only it is prepped and painted for interior use.



Now, the question ... what is the proper way to wire these lights on this type of ceiling? Is a typical ceiling box required at each light? If so, is it necessary to cut holes in the steel panels equal to the diameter of the boxes or can I use a smaller hole? If I use a smaller hole, how do I protect the wires from being cut or nicked by the steel panels? If a ceiling box is not required at each light, same question again ... how should the wiring be protected from damage by the steel panels?

To just simplify the question ... how should these lights be wired?

 

[v8garage]

A ceiling box is not required. Run conduit to the lights and the wiring is done in the body of the light fixture. The fixture itself serves as the "box".
V/8

 

[elevator joe]

How are you at bending conduit? If you don't feel like cutting holes in your steel ceiling,you can surface mount your lights and conduit.If it's done right,it;ll look pretty nice when it's finished.

 

[John in OH]

How are you at bending conduit? If you don't feel like cutting holes in your steel ceiling,you can surface mount your lights and conduit.If it's done right,it;ll look pretty nice when it's finished.

You and V8garage have a good idea regarding the use of conduit. I'm planning on having 3 lights on each of 4 switches so that I don't have to have all lights on at the same time if I choose not to.

I can readily run conduit between the light fixtures associated with each switch, but it would be very difficult to run conduit from the switches to the first light of each group. So if the wiring from each switch to its respective first light is run in a conventional manner, not in conduit, how do I wire to the first light? If a ceiling box is not required, how do I make the wiring penetration through the steel ceiling panel and into the fixture and protect the wire?

 

[Aceman]

Run conduit across the liner panel and set a 4 sq box at each light location. I assume your hanging them down on chain? If so, use a screw and washer(I prefer an acoustical self drilling lag screw, it's cleaner IMO)to secure the chain to the ceiling. Then use stranded MC(or aluminum flex and THHN) from the box ziptied down the chain right into the back of the light.

If you're running across the delta rib with your conduit, be sure to set your boxes on TOP of the rib. Not in the valleys, or else you won't have room to get your pipes out of the side of the box. You can cut spacers out of 1/2" pvc if you want to shim the box on either side of the rib to help stabilize it.

 

[W-Cummins]

If you're running across the delta rib with your conduit, be sure to set your boxes on TOP of the rib. Not in the valleys, or else you won't have room to get your pipes out of the side of the box. You can cut spacers out of 1/2" pvc if you want to shim the box on either side of the rib to help stabilize it.

With the panel profile he is running ( looks like menards pro-panel), he can attach the box to the pan of the panel and with 1/2" conduit it will run to the boxes just fine and he will not need to bend any offsets as the ribs are only 3/4" high.

I can attach a picture of some I ran the other day if he would like. I also attached the lighting directly to the tops of the ribs. That way it all lined up great with the conduit clamps mounted to the pans.

William...

 

[elevator joe]

If your walls are steel bend all of your conduit,if sheetrock maybe some remod boxes and fish your wires up to a j-box and transition to your conduit. The box stores carry different 90 degree and offset fittings if you don't want to bend pipe. Good luck take your time!!

 

[John in OH]

With the panel profile he is running ( looks like menards pro-panel), he can attach the box to the pan of the panel and with 1/2" conduit it will run to the boxes just fine and he will not need to bend any offsets as the ribs are only 3/4" high.

I can attach a picture of some I ran the other day if he would like. I also attached the lighting directly to the tops of the ribs. That way it all lined up great with the conduit clamps mounted to the pans.

William...

If you have some photos detailing the penetration of the wire into the light fixture and how you protected the wire that would be great! Protection of the wire where it passes through the panel and into the first box or light fixture is my major concern.

I'll be mounting the fixtures parallel to the major ribs and the fixtures will be surface mounted to the panels, not suspended.

 

[jvitez]

I'll be mounting the fixtures parallel to the major ribs and the fixtures will be surface mounted to the panels, not suspended.

Are you going to screw the metal fixture into the metal ceiling itself, or position them so you're screwing through the metal ceiling into the wooden truss bottoms? It would make a difference in how much weight you could have, ie metal vs PVC conduit if your area allows it. How will you mount the fixtures?

 

[John in OH]

Are you going to screw the metal fixture into the metal ceiling itself, or position them so you're screwing through the metal ceiling into the wooden truss bottoms? It would make a difference in how much weight you could have, ie metal vs PVC conduit if your area allows it. How will you mount the fixtures?

Will screw through the light fixtures directly into the bottom truss chords. Conventional wiring up to the first light fixture, then steel EMT conduit between light fixtures common to each switch. ..... At least that's the current plan.

 

[elevator joe]

John,Sorry no pics. See if you can find a 7/8"(unibit or step bit, the box stores usually cary them). It's a cone shaped hole cutter we use for going through light gauge metal.You could put up your light,and drill through your fixture and your ceiling at the same time. Put a 4"x4" j-box on one of your trusses and a short peice of pipe down to your fixture.Run your romex up into your j-box with a plastic bushing and you should be set.

 

[W-Cummins]

If you have some photos detailing the penetration of the wire into the light fixture and how you protected the wire that would be great! Protection of the wire where it passes through the panel and into the first box or light fixture is my major concern.

I'll be mounting the fixtures parallel to the major ribs and the fixtures will be surface mounted to the panels, not suspended.

Well here is what I have at the moment. The passage into the fixture is just through the normal knockout hole ( I don't know if I punched it or if it was there in the fixture as I did it a while ago. This install was unfortunately an after thought and I mounted the fixtures other places on the ceiling with boxes I mounted to the steel purlans and cut holes on the liner panel for them. Because I failed to plan this install before I installed the liner panels I had to surface mount it and also come out of an existing wall to power it.
So I guess you should tell us how your running your wires behind the panel sense you seem to be worried about protecting them when they pass through the liner. All my stuff in the walls and under the liner panel is MC/AC and is terminated into the boxes with a standard mc to metal box with an antishort bushing, adapters. I don't like the set screw conduit adapters and so I only use the compression style adapters for conduit and put the standard thread protectors on them too.

William....

 

[Aceman]

William, why couldn't you put that 4/0 metal box straight in line with that light fixture? You've got an offset from that light into the 4/0 box, then back to back 90's with a kick to get down the wall to the switch box. That's a lot of bends in a short space.

What it looks like you could of done is run a straight stick of pipe out of the light to the 4/0. Then punch right out of the opposite side, 90 down the wall and 90 into the side of the switchbox. That would have saved you an offset and a kick. Plus it would of looked a little cleaner IMO.

Not trying to knock your work, just trying to offer some constructive criticism.

 

[W-Cummins]

William, why couldn't you put that 4/0 metal box straight in line with that light fixture? You've got an offset from that light into the 4/0 box, then back to back 90's with a kick to get down the wall to the switch box. That's a lot of bends in a short space.

What it looks like you could of done is run a straight stick of pipe out of the light to the 4/0. Then punch right out of the opposite side, 90 down the wall and 90 into the side of the switchbox. That would have saved you an offset and a kick. Plus it would of looked a little cleaner IMO.

Not trying to knock your work, just trying to offer some constructive criticism.

Your correct it's rather "wonky" I started out with the setup on the wall, and should have come out of the box on the side but my thought was "going up" so come out of the top of the box. That of course made much harder bends than needed. The addtional offset was another (over killed) plan. I was just going to run the light fixture in a straight line to the box but looked at it and "over thought" the plan, and decided that it should go over the purlan (so I could use long screws to attach the fixture to the panel and the purlan), of course as I had at that time already mounted the rest of the run, I then had to bend another offset....

So now you would have to smash the fixture off with a sledge hammer rather than pry it off with a crow bar to accidentally knock if off the ceiling.

William....

 

[jvitez]

John in OH: does your jurisdiction allow PVC conduit? It seems for what you want to do PVC would be far easier to work with than metal conduit. The "junction box to conduit to fixture number 1" sounds like a good one to me.