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#173018 - 12/31/07 01:18 PM long offsets in small diameter pvc.
goodwill Offline
Member

Registered: 08/23/04
Posts: 53
Loc: Madison, WI, USA
so I bought the greenlee hot blanket for 2"-3" pvc, with the thought that (because of it's longer length) I'd be able to use it on 1/2" and 3/4" pvc to make nicer looking offsets.
but on the pouch it comes in it cautions not to use it on pipe smaller than 2". now I'm scared i'll wreck it.
I have the small hot blanket, but as you know it is very short. if you have to make a big offset, it either turns out butt ugly, or you do a series of offsets, also butt ugly.
my other option is to look into a 120v hot box. we have one, but it's 240v(and draws 28amps). not good when your only power is an extension cord.
where i work the muffler trick wouldn't be kosher.

just wanted to pick brains for a nicer looking big offset.
(I know...it gets buried anyway..just picky I guess)

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#173024 - 12/31/07 02:20 PM Re: long offsets in small diameter pvc. [Re: goodwill]
KJay Offline
Member

Registered: 11/27/07
Posts: 763
Loc: MA, USA
goodwill,
In the past, I used the 3” blankets for 1/2” to 1” instead of using the right size. It definitely overheats and shortens the lives of the blankets. I don’t do it anymore though, now that those Greenlee 3” blankets are in the $400.00 range.
Now what I normally use is a large Master 750/1000 degree heat gun. It doesn’t take that long to heat small diameter PVC if you tape the ends of the pipe. You have a lot more control over the heat and you can also heat a larger area all at once than the small blanket does for longer radius sweeps and bends.
I bend offsets for LB’s with the pipe in place, as long as it doesn’t present a fire hazard, which is almost never, even with wood shingles and clapboard. I use a wet rag behind the LB for a building with vinyl siding.
The only real down side, as least for me, is that I have to stay with the pipe as I’m heating it, so I can’t do other tasks.
I’ve even used the Master heat gun on 2" in a pinch when I didn't have a blanket in the truck.

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#173025 - 12/31/07 02:20 PM Re: long offsets in small diameter pvc. [Re: goodwill]
sparkyinak Offline
Member

Registered: 07/08/07
Posts: 1295
Loc: Alaska
I have use my big blanket on small diameter pipe. This is not a recommendation (CYA clause). I kept a close eye on it and never leave it coiled while energized. Being that it is a heat mat that is covered, it can over heat and scorched the pipe if you are not careful.
_________________________
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#173030 - 12/31/07 02:57 PM Re: long offsets in small diameter pvc. [Re: sparkyinak]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Actually,
I use a LOT of PVC conduit here in NZ.
Smaller sizes are usually bent here with an internal bending spring, with a quick rub of your hand on the conduit often warms it enough to soften it enough to give a good bend.

It is common to see an electrician here on any given commercial or industrial site, bending the PVC just under their knee cap (with the knee bent).

Larger sizes like 2" and bigger can be carefully warmed with a heat gun before bending, the real key is not to over-heat the PVC as it will distort the pipe seriously when a bend is attempted.
It's best to take your time with PVC, it doesn't take too kindly to being abused when it is softened.
_________________________
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#173031 - 12/31/07 02:59 PM Re: long offsets in small diameter pvc. [Re: sparkyinak]
canuck Offline
Member

Registered: 07/15/06
Posts: 27
Loc: Canada
My boss will sometimes cut a prefabricated 90 degree bend and cut in half to make two 45 degree bends. Might not be practical but it's and idea.

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#173032 - 12/31/07 03:37 PM Re: long offsets in small diameter pvc. [Re: goodwill]
BryanInBalt Offline
Member

Registered: 05/11/07
Posts: 47
Loc: Baltimore
 Originally Posted By: goodwill
so I bought the greenlee hot blanket... just wanted to pick brains for a nicer looking big offset.
(I know... it gets buried anyway..just picky I guess)


uh huh ;\)

I go with the smaller electric hot box when I have one.
But if it is really gonna be buried... go for the burnt marshmallow effect!
_________________________
Design-Build isn't supposed to mean design *as* you build.

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#173038 - 12/31/07 05:34 PM Re: long offsets in small diameter pvc. [Re: BryanInBalt]
electure Offline

Member

Registered: 12/24/00
Posts: 4226
Loc: Fullerton, CA USA
352.24 Bends — How Made.(blah, blah, blah...) "Field bends shall be made only with bending equipment identified for the purpose."

A heat gun, blowtorch, etc. isn't identified for the purpose.


Offsets in 1/2", 3/4", & 1" can be bent cold with a standard bender. Just use the proper size.

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#173042 - 12/31/07 08:28 PM Re: long offsets in small diameter pvc. [Re: electure]
KJay Offline
Member

Registered: 11/27/07
Posts: 763
Loc: MA, USA
Hi electure,
I know that many electricians use hand benders for RNC because they have the required radius, but where can I find some confirmation that it’s okay to use EMT/RMC/IMC benders for SCH 40 and SCH 80 RNC?
The reason I ask is because I bought all new 1/2" to 1-1/4" replacement Ideal benders this year and they didn’t list any info on using them to bend RNC.
I have never been able to find anything about it on Carlon’s technical information website.

Thanks

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#173044 - 01/01/08 03:27 AM Re: long offsets in small diameter pvc. [Re: electure]
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
 Originally Posted By: electure
352.24 Bends — How Made.(blah, blah, blah...) "Field bends shall be made only with bending equipment identified for the purpose."

A heat gun, blowtorch, etc. isn't identified for the purpose.


Nope.....but none of those items bend RNC, they heat RNC. (I am only 1/2 joking...think about it)

My hands bend RNC and they are identified by me for bending.

It's really a very poorly worded section of code that is simply ignored out in the field.
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#173045 - 01/01/08 04:38 AM Re: long offsets in small diameter pvc. [Re: iwire]
wire_twister Offline
Member

Registered: 07/25/07
Posts: 265
Loc: Georgia USA
I have a Greenlee hotbox listed for use with 1/2 to 2 inch conduit, it has a 120 volt 15 amp plug on it. A buddy of mine has the same heater but his came with a 120 volt 20 amp plug, go figure.
_________________________
Jimmy

Life is tough, Life is tougher when you are stupid

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