PVC expansion joints ?

[mjgilmore54]

I am installing a 80 ft. horizontal run of pvc conduit on side of a commercial building for a new 200 amp service. using 3/0 copper in 2 inch pipe. Being that one end of the conduit ends at the weatherhead and is basically free to move with expansion and contraction is there a need for an expansion joint ? Can't seem to find an answer on this anywhere.
Thanks

 

[augie47]

No need since the conduit is not between "fixed points"(assuming your weatherhad is not captive) . Be sure to use a strap that will allow movement.


352.44 Expansion Fittings. Expansion fittings for PVC
conduit shall be provided to compensate for thermal expansion
and contraction where the length change, in accordance
with Table 352.44, is expected to be 6 mm (1⁄4 in.) or
greater in a straight run between securely mounted items
such as boxes, cabinets, elbows, or other conduit terminations

 

[fmtjfw]

Are there any bends? I would assume that you have a vertical portion from the meter to the level of the weatherhead and then a long horizontal run to the actual head. If you install the wires in the cold will the length of wire be long enough in the heat? What is the expansion of 80 ft of pvc for the temperature range? Do you expect the weatherhead openings not to abrade the insulation?

 

[beanland]

Wear and Tear

Wear and Tear

I would be concerned that the normal expansion and contraction of the PVC would place stress on any fixed mounting points and lead to eventual PVC failure. If there are sufficient bends and sweeps, they can allow for some expansion. If it is a long straight run, adding an expansion joint may not be required by NEC but may be appropriate.

 

[kwired]

I would be concerned that the normal expansion and contraction of the PVC would place stress on any fixed mounting points and lead to eventual PVC failure. If there are sufficient bends and sweeps, they can allow for some expansion. If it is a long straight run, adding an expansion joint may not be required by NEC but may be appropriate.

Most important is support methods that do not clamp onto the raceway but instead simply support it yet allows for movement, this applies whether you use expansion fittings or not.

An elbow that is not securely fastened in any way does allow for expansion from two different directions, but remember the longer the run the more that elbow is going to move.

 

[Cow]

I've used some strut straps made for refrigeration lines before. The type with the rubber insert that gets clamped between the pipe and strap. Even with the strap tightened down, you could still slide the pipe through it with little effort. Worked great.

https://www.grainger.com/Grainger/ZSI-Cushioned-Clamp-4MVD8?Pid=search

 

[RichB]

And yes--there is a PVC expansion joint--looks and works just like the ones for RMC--we use them alot in bridge s at the construction joints

 

[kwired]

And yes--there is a PVC expansion joint--looks and works just like the ones for RMC--we use them alot in bridge s at the construction joints

There are likely more people aware there is PVC expansion fittings than there is people aware that there is expansion fittings for metal raceways. Larger commercial/industrial project installers are likely the majority of those that ever see the metal raceway expansion fittings.

 

[iwire]

Here is what can happen when you do provide expansion fittings at each end of a 150' - 175' run of PVC but the supports are too tight to allow the PVC to slide through them.

The PVC stayed attached to the struts but the struts sheared off the hardware holding them to the building.

You could see by the scratches in the paint that this had taken a long time to happen, I imagine once enough broke free it came down like a zipper. Luckily it stopped on its own and we were able to put it back into place.