Heating PVC Conduit

[steve holt]

According to the manufacturer, the max heat that pvc conduit can be exposed to is 120 F. That being the case, you are not allowed to heat the pipe in order to make bends. Is that correct? I can understand the limitation as it relates to a wiring system, but not to the installation.

 

[tom baker]

Is the 120 degrees max ambient?

 

[kwired]

Yes you can heat it to bend it.

If the finished installation is subject to high temps it may begin to droop.

Have seen that happen too. Hog house, power washer with kerosene heater, low ceiling, conduits too close to heater exhaust outlet.

 

[steve holt]

Is the 120 degrees max ambient?

The manufacturer just refers me to NEC 352.12(D) PVC conduit has a maximum ambient termperature of 50C or 120F. as for bending, they refer me to NEC 352.24 Bends shall be so made that the conduit will not be damaged... Field bends shall be made only with identified bending equipment.

 

[infinity]

It's seems to me that any commercial heater type bender heats the PVC well above 120°.

 

[Cow]

Sometimes you just have to use common sense. Or you will twist yourself in circles trying to follow codes or guidelines.

If I can heat and bend pvc with a blanket, hotbox, or propane torch and you can't visibly see anything wrong with the conduit after the fact, does it really matter what temp I used to bend it?

 

[Rock86]

Sometimes you just have to use common sense. Or you will twist yourself in circles trying to follow codes or guidelines.

If I can heat and bend pvc with a blanket, hotbox, or propane torch and you can't visibly see anything wrong with the conduit after the fact, does it really matter what temp I used to bend it?

I agreed with you up until you said propane torch. Unless you show me a UL propane torch or propane torch attachment, I would argue that a propane torch (although effective) is not considered a piece of "identified bending equipment."

Now... with that being said... I knew a guy who took a propane grill and reworked the guts a little to make a very cheap, and effective PVC pipe forming machine.

 

[infinity]

I've used a gas grill several times and it works very well. And unless your PVC looks like a well done steak after it's bent who's going to know how you heated it up.

 

[ActionDave]

My favorite was when we had to pour out a can of PVC glue in a trench and set it on fire

 

[480sparky]

Vehicle exhaust works well. Or the trencher exhaust.

 

[hillbilly1]

I agreed with you up until you said propane torch. Unless you show me a UL propane torch or propane torch attachment, I would argue that a propane torch (although effective) is not considered a piece of "identified bending equipment."

Now... with that being said... I knew a guy who took a propane grill and reworked the guts a little to make a very cheap, and effective PVC pipe forming machine.

That was innovative! LOL!

 

[Coppersmith]

Pour glue on conduit and set it on fire, done that.
Heat it with a propane torch, yup usually do it that way. Fan tip.
Hot box, fancy and hard to carry on a service truck, but done that.
You know if you are burying it, nobody will notice if it's burned on the outside.

 

[hillbilly1]

I've used portable electric box heaters before they started installing tilt sensors.

 

[kwired]

I have old baseboard heater and a piece of rain gutter to put over the top, works great and cost basically nothing, only thing that makes a "hot box" better is the reflective surfaces inside of it.

Also have a radiant propane heater that goes out where there won't be power to utilize the baseboard heater.

 

[Cow]

I agreed with you up until you said propane torch. Unless you show me a UL propane torch or propane torch attachment, I would argue that a propane torch (although effective) is not considered a piece of "identified bending equipment."

Now... with that being said... I knew a guy who took a propane grill and reworked the guts a little to make a very cheap, and effective PVC pipe forming machine.

 

[Eddie702]

I have offset 2" PVC with a heat gun and it worked fine. never tried it on anything larger

 

[Carultch]

According to the manufacturer, the max heat that pvc conduit can be exposed to is 120 F. That being the case, you are not allowed to heat the pipe in order to make bends. Is that correct? I can understand the limitation as it relates to a wiring system, but not to the installation.

Consider another similar example of a splice made with heat shrink. The spliced assembly is only rated for 90C, but you have to heat the shrink tubing to a lot more than 90C, so it can shrink upon heating as the name implies. The 90C rating doesn't mean that it can't ever exceed 90C. Instead, the 90C rating is the temperature it is limited to, during its operation.

The 120F temperature is the environmental temperature it is limited to withstand during operation. This doesn't mean that it is never allowed to exceed 120F in its lifetime since leaving the warehouse, because heating it is how you make field-bends. Just that it isn't permitted in an environment exceeding 120F. Otherwise the environment itself would become the heating blanket, and it would permanently bend under its own weight.

 

[kwired]

Quick google check says PVC should be heated to 225 to 275 F (depending on size and how much bend is desired) to achieve uniform softening of the pipe material. Also says most polyolefin shrink tubes recommend about 90C shrink temperature though teflon containing tubes can need 250C.

 

[jon176]

The 'Hot Bend' is a propane torch made for bending PVC conduit. Buried or not, I think charring the outside of the conduit damages it's integrity.

 

[steve holt]

Thanks for all the input. Over the past almost 40 years I have been an electrician, I have used every one of the methods mentioned, except for the one where you pour glue on it and set it ablaze! I have to draw the line somewhere. I know what is practical, but in some cases have to provide documentation, and that is where I am running into trouble.