PVC Expansion

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ElectricianJeff

Senior Member
Location
Southern Illinois
Last year I put up a run of 3/4" PVC for 4 lights than ran about 50' down the side of a small commercial building. The run was up under some eaves and I thought the sun wouldn't effect it. I strapped the run every 4'.

I checked it recently and it has become real wavy due to expansion and now looks like crap. I contacted the owner and offered to fix it for free. It worked out good because he has a bunch of other work he wants me to do while I'm there.

My first thought is to put in some PVC expansion couplings between each fixture. I've never used small expansion couplings in this type of application before and want to make sure I get it right this time.

Do I want to leave the clamps a little loose to allow for movement? Should I tear down the whole thing and run emt? Any other tips would be appreciated.

Jeff
 
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SEO

Senior Member
Location
Michigan
Follow the instruction with the expansion fitting and make sure that you use pvc clamps or straps. They are designed to allow for expansion and contraction and allow the pvc to slide back and forth. A normal hw or emt strap will not. Also strap per section 352.30 max 3' for 3/4" pvc.
 
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augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Since you obviously have concern as to the aesthetics, I don't think you will be happy until you run EMT.
If you decide to stick with PVC and add expansion joints, the straps would need to allow movement.
 
chris kennedy

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
ElectricianJeff said:
I strapped the run every 4'.
Click to expand...

Should have been every 3', 352.30.

Any other tips would be appreciated.
Click to expand...

You will find that the expansion coupling will hold the PVC about a ?" off the wall. Since the fitting is about a foot long this puts a strap 1' from each end. I heat a quick offset on both sides of the fitting allowing the 2 pieces of the fitting to properly mate. Also note that if you pull the coupling apart a bit you will find a black line that shows the midway point. This is when I set the during the install.
 
cadpoint

cadpoint

Senior Member
Location
Durham, NC
Thats some service your offering! Seems logicial enough to go with EMT.

Don't forget to include
raintight3.4conn__31865_thumb.jpg
and
raintight3.4cplg__45029_thumb.jpg

both UL Approved Waterproof Connectors and Couplings.

The last ones I touched had green on the compression bolt or on the center chassis.
 
S

SEO

Senior Member
Location
Michigan
chris kennedy said:
Oops, sorry to step on your toes SEO.
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No problem I do it probably as much as anybody. Your not stepping on my toes your just reinforcing my comment.:grin:

The offset method you use works well, what we usually do is use pvc back-straps which set the pvc off the wall aprox 3/8" and allows expansion fittings to be installed and you usually can go into pvc boxes without an offset. But I agree an emt system will not give you some of the problems that a pvc system will.
 
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hardworkingstiff

Senior Member
Location
Wilmington, NC
cadpoint said:
Thats some service your offering! Seems logicial enough to go with EMT.

Don't forget to include
raintight3.4conn__31865_thumb.jpg
and
raintight3.4cplg__45029_thumb.jpg

both UL Approved Waterproof Connectors and Couplings.

The last ones I touched had green on the compression bolt or on the center chassis.
Click to expand...

Funny thing, here in Wilmington, NC, the inspectors are pretty sharp and pay attention to details but I don't think they enforce this. They still let the old compression pass as raintight.
 
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