PVC Expansion Coupling Question

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Looking for a little help on using an expansion coupling.
1 1/2 in PVC - total run of 65 ft as follows: 5 ft vertical, 50 ft horizontal, 10 ft vertical. Only a portion of the horizontal run (5 ft) and the 10 ft vertical section will be exposed to direct sunlight, and then only for about 5 hours per day.

What advice does anyone have about use of a expansion coupling in the 50 ft horizontal run? I've read some literature from Carlon and shouldn't have any problem setting the piston opening during installation.

My question relates to the best practices for the actual installation.

Where in the 50 ft run should I position an expansion coupling?
I'm thinking mount it near one end and strap the barrel end tightly.
Then strap the piston end of the conduit run (something short of 50 ft) somewhat loosely.
On which end should I install the coupling, the sunlight side?
Any helpful comments would be appreciated.
Thanks,
 
Re: PVC Expansion Coupling Question

As long as the piston can absorb the max expected expansion, it can go at the end.

"I'm thinking mount it near one end and strap the barrel end tightly.
Then strap the piston end of the conduit run (something short of 50 ft) somewhat loosely."
Seems like a good way to do it.

I have not done this, even in the cool NW we don't see a lot of PVC outside on buildings.
Even supported at the min. per code the PVC sags, I would consider using sch 80.
 
Re: PVC Expansion Coupling Question

Tom, excellent comment about the "sag" factor. Given the visibility of this installation, a "saggy" run would be unsightly. Sched 80 would be much better.
Thanks,
 
Re: PVC Expansion Coupling Question

I would of suggested EMT but there is the issue of the listing being pulled for emt compression connectors and such.
I looked into fiberglass once, its advertised but the availability is poor.
 
Re: PVC Expansion Coupling Question

I've been down this road a time or two. In the area that I live the AHJ requires the expansion be calculated at 100F. This is the estimated maximum temp differential that the PVC is likely to see. At this diff. anything over 6' in length must have provision for expansion if it is between securely mounted items (347-9.), (IE, it can't grow or shrink without something moving). If I'm installing short runs that are more than 6' between turns I often utilize the location of the mounting straps to allow the required movement. PVC is required to be fastened within 3' of each box or turn, so I mount the conduit in oversize straps and anchor the pipe 3' beyond the turn. This allows the pipe to move. The code requires expansion fittings to allow movement, not expansion "joints" (347-9.). I've never had a PVC system to break because of expansion doing it this way. If the run is long, this procedure won't allow enough movement and I have to use a expansion "joint". For your horizontal run of 50', a joint is probably necessary. At 100F differential it will grow about 2". I would place the joint at the end of the run and firmly secure the downstream end. All of the upstream pipe would be in oversize (next largest) straps. I don't have a lot of confidence in the expansion joints that are available. If they are not properly supported they can bind or allow water to enter the conduit. In my experience , a good PVC installation can be "shook and rattled" before the wire is pulled.
I hope this helps
steve
 
Re: PVC Expansion Coupling Question

I don't know if this would apply, but as part of our "code" at the airport, expansion fittings are always required when crossing building expansion joints if they exist, with the conduit run(s). That way, all of the "engineering" is done for you.One side is firmly anchored, while "normal" support spacing for the conduit run is maintained on the opposite side. Make sure you "set-up" the fitting for the time of the year you are in. We have seen fittings pulled apart and in other cases bowed out due to wide temperatures we see where we are. I apologize for not knowing what the coefficient of expansion is for PVC just now, so I feel unprepared to answer in a more detailled manner.
 
Re: PVC Expansion Coupling Question

Thanks so much to everyone for sharing their wisdom and knowledge. It's people like you who make this Code Forum so great!
Appreciate it.
 
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