Heating PVC and THHN

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chris kennedy

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
I have seen people heat PVC with wire in it. Now I have a situation where this could be handy.

THHN=90?C or 194?F

Seems to me PVC would have to be hotted then 194? to bend.

What do you think?
 
chris kennedy said:
I have seen people heat PVC with wire in it. Now I have a situation where this could be handy.

THHN=90?C or 194?F

Seems to me PVC would have to be hotted then 194? to bend.

What do you think?
Click to expand...

I really don't know the answer but I would bet the temp. on the outside is much hotter than the temp where the wires are. I assuming you're talking blanket and not torch.
 
I just came from there and don't have to heat it.

Still curious if it would damage the insulation.
 
I don't know either. I have never bent PVC with wire in
it, but it sounds like a risky operation to me.

While I have bent PVC, another thing that would make
me nervous about a piece already installed is it collapsing
or kinking. As you know, you are supposed to plug
larger pieces, which would probably be impossible
if already installed.

A note with a Greenlee 860-3 blanket says "temperature
over 149 degrees C".

I am guessing, but since PVC is so much denser than air
and the air in the pipe is totally enclosed, I wouldn't
assume that it is much cooler in the pipe than the pipe
itself.

It would be interesting to megger wires before and
after to see if the insulation were affected.
 
I don't think so, try this.

I don't think so, try this.

chris kennedy said:
I just came from there and don't have to heat it.

Still curious if it would damage the insulation.
Click to expand...

Grab some sraps of wire and a piece of pipe and do a test run. :smile:

I use a torch sometimes. I've done it with wire in the pipe before. I get it to just the point I need it, shape it and cool it with a wet towel. The exposure time of any heat to the conductors is minimal.
 
frizbeedog said:
I use a torch sometimes. I've done it with wire in the pipe before.
Click to expand...
352.24 Bends ? How Made. Bends shall be so made that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. Field bends shall be made only with bending equipment identified for the purpose. The radius of the curve to the centerline of such bends shall not be less than shown in Table 2, Chapter 9.

​
I can not imagine that you have a torch that is identified for the purpose or that you can use a torch without scorching the outside of the conduit. Additionally, if you can't assemble a conduit without the conductors enclosed, how can you work a piece of PVC with the conductors enclosed? Does anyone know that the conductor insulation will not be damaged when the temperature exceeds the pliability point of the PVC?

In my opinion, this can not be done while protecting the conductors. Pull the conductors out, do the work correctly, and pull in new conductors. :cool:
 
charlie said:
.....identified for the purpose. ....
Click to expand...


Propane torch... trencher exhaust... heat gun...... PVC glue poured on the ground and set afire.....

"Hey, it works!"..... that identifies it for the purpose! :grin: :grin:
 
charlie said:
I can not imagine that you have a torch that is identified for the purpose or that you can use a torch without scorching the outside of the conduit.
Click to expand...

He might.

HotBend

I will admit that this rule (identified for the purpose) is pretty much universally ignored. It's not right but it is a reality.

Plumbers torches, electric heat guns, the exhaust from a truck, the output of a temporary job heater are all methods commonly used for PVC bending.

You can easily burn PVC with equipment designed exclusively for bending.
 
480sparky said:
"Hey, it works!"..... that identifies it for the purpose!
Click to expand...

I assume your comment was a joke but just to be sure, this is the definition, pay special attention to the FPN. :D
Identified (as applied to equipment). Recognizable as suitable for the specific purpose, function, use, environment, application, and so forth, where described in a particular Code requirement.
FPN: Some examples of ways to determine suitability of equipment for a specific purpose, environment, or application include investigations by a qualified testing laboratory (listing and labeling), an inspection agency, or other organizations concerned with product evaluation.

​
I don't mean to insult you, just trying to be clear. :)
 
:)
charlie said:
352.24 Bends ? How Made. Bends shall be so made that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. Field bends shall be made only with bending equipment identified for the purpose. The radius of the curve to the centerline of such bends shall not be less than shown in Table 2, Chapter 9.

In my opinion, this can not be done while protecting the conductors. Pull the conductors out, do the work correctly, and pull in new conductors. :cool:​
Click to expand...


....but I have skills my freind. :cool: :smile:

When I pick up my torch and choose to use it, I'm am at that time identifying it for the purpose. ;)

...keep in mind, Chris was asking about a specific situation. Sometimes in a pinch, that's just something that might have to be done. If done correctly, and if you know how to pull it off.

....in a perfect world, you know.​
 
I bet you could do it.

A few weeks ago I was called to replace a section of pvc that had melted in a potato storage. I cord end laying on the pvc had shorted out and melted the pvc for about six inches, it was black. When I pulled the wire out(THHN), only one neutral was brown but all the other wires were fine. Even that neutral when closely inspected was only discolored, there were no breaks, cracks, etc and the insulation still remained flexible. So I'd say if you were just heating it to bend it and not turn it black/melt it, you'd be okay. Not that I'd use it as an excuse to do it all the time, but if the situation calls for it...
 
charlie said:
Still, in my opinion, a normal torch is not identified for the purpose. :mad:
Click to expand...

I agree 100%, you are correct.

If I just lay PVC in a curved trench should the trench be identified for the purpose? :cool:

IMO that is a poor section of code, I should get off my rear and try a proposal to it.
 
iwire said:
I agree 100%, you are correct.

If I just lay PVC in a curved trench should the trench be identified for the purpose? :cool:

IMO that is a poor section of code, I should get off my rear and try a proposal to it.
Click to expand...

Can we have a preview. :)
 
Do conduit systems need to be complete berfore installing conductors????

300.18 Raceway Installations.
(A) Complete Runs. Raceways, other than busways or exposed raceways having hinged or removable covers, shall be installed complete between outlet, junction, or splicing points prior to the installation of conductors. Where required to facilitate the installation of utilization equipment, the raceway shall be permitted to be initially installed without a terminating connection at the equipment. Prewired raceway assemblies shall be permitted only where specifically permitted in this Code for the applicable wiring method.
Click to expand...
 
charlie said:
352.24 Bends ? How Made. Bends shall be so made that the conduit will not be damaged and the internal diameter of the conduit will not be effectively reduced. Field bends shall be made only with bending equipment identified for the purpose. The radius of the curve to the centerline of such bends shall not be less than shown in Table 2, Chapter 9.

​
I can not imagine that you have a torch that is identified for the purpose or that you can use a torch without scorching the outside of the conduit. Additionally, if you can't assemble a conduit without the conductors enclosed, how can you work a piece of PVC with the conductors enclosed? Does anyone know that the conductor insulation will not be damaged when the temperature exceeds the pliability point of the PVC?

In my opinion, this can not be done while protecting the conductors. Pull the conductors out, do the work correctly, and pull in new conductors. :cool:
Click to expand...
A customers gas bbq works just fine keep spinning it , It can be done with a torch but it is very easy to scorch, worms usually dont rat on electricians same as groundhogs and rabbits. I do have blankets benders and vipers btw but sometimes in an emergency you have to do what you have to do. Cutting pvc in a trench with mason line is an old favorite also.
 
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