Hi all,
I am designing a lighting retrofit where the Owner requests a one-for-one replacement of highbay lights. The lights are currently hard-wired, and the Owner wants the new lights to be connected via cord and plug. There are a few hundred fixtures and downtime (plus other costs) needs to be limited. The hardest part to factor is the conduits disappear up into a fabric insulation ceiling which presents two problems. One, the insulation may or may not be hiding junction boxes. And two, it is difficult (impossible) to visually trace conduits to see what goes to where. I'm concerned that we will need to cut the conduits a few feet short to allow the outlet box to be installed, but in cutting the conduit short we will sever the wire within it. It will be hard to pull back wire given the conditions.
I tentatively proposed a solution that sounds viable but I've never heard it done before: use something like a pipe-cutter (like used on copper plumbing pipes) to cut two feet off the EMT without damaging the wires within. Drop off the two feet and slide a box over the end. Is this something that is done? The maintenance folks thought it was a slam dunk idea but before I sent it out for public bid I figure I better make sure it is a viable option.
I'm guessing I'll hear other solutions from the community, so will add a little more information. Most of the fixtures already have a cord and plug, we're talking about maybe 15% of the fixtures. We'd like to keep them all in the same location at the same height - it's a nice existing grid that lines up with a number of other systems, limiting the ability to move things over or drop the heights. It's a high-profile event space, with some arena seating that will keep some spectators near eye level with the lighting, bolstering the need to keep it looking clean and neat. All that to say it would be really nice to cut the conduit a couple feet short without severing the wire.
Let me know your thoughts. Thanks!
While some of the recommendations are workable-- albeit difficult to achieve with varying results. Some may not give you peace of mind after all is said and done.
The “scoring approach” would certainly work by using a plumber's tube cutter. The problem with this is -- it will leave a razor-sharp burr that will likely cut though the insulation. Deburring it with any type of tool also has the potential of further damage to the insulation.
Scoring the conduit with pipe cutter won't be a “cake walk” either. You need ample clearance to turn the tool as you go around the circumference of the tubing. This will only work on EMT not with rigid conduit.
I've done this when I converted my sodium security lights on both sides of the house to LED Luminaire. It was mounted about 15 feet high—and the riser was one solid ten foot surface mount EMT. I had to mount the LED fixture lower than 15 feet.
Pulling the wires back was not an option because the conduit disappears through the wall to a junction in a soffit inside the house.
So, I used a high speed Dremel grinding tool with metal cutting disk about 1 ½ inch diameter. The 1/8 inch dia shank is where the cutting disk is screwed into. To prevent the cutting disk from cutting too deep (hence injuring the conductors) I slipped a piece of plastic ferrule on the Dremel shank, and exposing enough of the cutting blade to cut through the wall thickness of the pipe.
You don't have to cut all around the circumference of the pipe—only about three quarters of the pipe circumference is more than enough to snap it clean. The Dremel tool doesn't need a lot of clearance from the wall.
A minimal rough edge on the pipe can be smoothened (if you so desire) even with your wife's or girlfriend's nail file.
Just let her know before hand though—not spoil her holiday festive mood. LOL
Now, I can sleep better-- not having to worry about short-to-ground problem in high humidity and wet conditions this time of year. The inspector gave me a "high five" when I told him how I did it.
If the above doesn't give you enough peace of mind and confidence-- that the work is done safely-- you can get small piece of “fish paper” used in motor rewinding to insulate the stator magnet wire from the laminated core.
This fish paper is not the type that is used for wrapping salmon fillets at Walmart.
This is the one used in electrical repairs and manufacturing. . . and available on line.
BTW: I hope you are not like me. . .I have a mild OCD.
I'm not always satisfied with how things are done satisfactorily - -a hard-to-please codger.