How do you bend PVC electrical conduit
In the many many commercial construction jobs I’ve been to I’ve consistently seen PVC electrical conduit runs where the conduit is bent all sorts of ways, such as prior to a slab pour. I’m talking nice smooth bends, bends of varying angles, S bends, etc, as if it were molded and shaped that way, but I know darn well they ain’t nothing but straight pieces of PVC conduit somehow bent, under heat I presume.
So what is the magic to this? How do you do it? I can’t imagine heating it with a torch to make it pliable….or is that the method after all? In the next couple of months I’m gonna have a job where doing this will save me a lot of effort and time, so if you know how to do it, please be detailed in the technique, as I would intend on trying it.
Thanks!
Replies
You can get commercial heaters for bending PVC. One sytle is an electric blanket you wrap around the pipe and hold with velcro. Another is a box with holes in the end and a flip top lid. The 98/99 MSC catalog has two of the blanket type, called PVC conduit heating blankets and one of the box type, called an electric PVC heater/bender. I'd give you order numbers, but they might have changed by now, and the names are more likely to still be searchable.
Hot water will also work, and I've even heard of people bending PVC by warming it with the exhaust from a truck.
We do it over a gas grill. The best tip is to tape off the ends of the piece you are bending to hold the heat where you put it. I am sure that the blankets or box are RIGHT the way to do it.
Greenlee makes a hinged bending oven. See http://www.greenlee.textron.com/
heat gun
The best employee you can have but you wouldn't want him as a neighbor " He the shifty type"
Pyroman,
If you're bending 3/4" pipe a blanket or heat gun will soften the pipe up enough to put a "kick" in it.You wouldn't be able to bend a 90 degree bend though.The problem with these two methods is that they can't spread the heat out far enough to get a smooth radius.To bend sweeps and larger pipes you need to use a hot box.I myself have never seen anything other than the Greenlee brand.The most common size bends up to 2",the big one up to 4".You put the pipe in,close the door,and rotate the pipe so the heat is evenly distributed.When you can lift up on the pipe on one side of the box and the other side lags a bit in coming up,it's just right.If you leave it in longer, the pipe will get rubbery,like a limp noodle,and the walls will collapse a little ,making it harder to eventually pull wire.Never walk away from it unattended.When it starts to scorch the pipe,the gases emitted are very poisonous.When you walk up to a bender that has heated a pipe beyond "spaghetti" your lungs instinctively stop breathing because the fumes are so bad.It's the reason I hate those cheap PVC electrical boxes.
Barry
Pyroman,
We needed to bend alot of 2" on a job so I built one for my electrician buddy. 18x18x48" metal box with the heater part of an old HLV unit. A piece of 4" metal duct to recirculate. Cost about $4 and 2 hours time. Takes about 10 minutes to bend 2" but you gotta watch it close. He's still using it.
KK
Heat gun, propane torch, electric oven type heat box, hot blanket pipe heater, hot tanks. Depends on the size of the pipe and how many and to what degree I'm bending. 90s and offsets take more time a simple kick and smaller conduits are faster than larger. In a pinch I have used a hibachi, campfire, truck exhaust. Whatever it takes.
Taping the ends holds in the heat and may help keep the pipe from collapsing. Dry sand,or so I have been told, will too but I have never taken the time. You have to heat it, heat it evenly, without burning it. Inspectors frown of scorched conduits as it does substantially weaken it. The purpose build heaters are easier to use but the torch is handier, don't need power and is more often at hand. Heat guns are less likely to scorch, might be a bit faster than a torch but needs power.
A pair of leather gloves, a few rags and a spray bottle full of water, for freezing it when you get a section right, help greatly. I like to draw what I'm after on a flat surface, concrete slab is good. Try to set up out of the wind.
Point sources like heat guns have to be kept moving. Stop and reverse off the pipe otherwise you get a hot spot, an uneven bend or a collapsed conduit. Ovens usually do better if you spin the pipe.
Liquid heaters, an insulated tank of liquid, looks like antifreeze, kept at something like 400F, are the best but they are not cheap. You can drop in the length and it comes out the perfect noodle temperature. Only see these on big jobs usually. They also can cause nasty burns. On the up side they are nice for boiling bag lunches. Just hose off the solution before taking your jackknife to the bag.
Blankets are nice. A bit expensive unless your doing a lot of bending and they need power. Just wrap, plug in, turn the knob to what you guess will do it. Shake the conduit once in a while, short while as they can be fast, when it feel right remove and hold until it sets how you want. A quick spray will cool things down quickly.