Never had a problem with PVC on flat roofs when supported properly and proper expansion fittings are used (and directions followed explicitly). PVC expands/contracts about 4 inches for every 100 ft of pipe for a 100 degree F change. It's critical to know the temperature when you are doing the installation and figure out where that falls in your temperature range window. Since it rarely gets much below freezing in Southwest Florida, the temperature window here may be smaller than some of you experience, but I've never had to use more than one or two expansion fittings in a straight run of pipe (good route planning is helpful).
I've never been a big fan of long conduit runs on the roof anyway (get's pretty hot here on roofs). Ideally we get into the building as soon as possible. How does the Rubber Triangle Co product price compare to Durablock? Those things can be expensive! Another reason to get inside the building quickly... Jason From: [email protected] [mailto:[email protected]] On Behalf Of Glenn Burt Sent: Thursday, December 22, 2011 1:21 PM To: 'RE-wrenches' Subject: Re: [RE-wrenches] Expansion on conduits on commercial roof tops! If you are talking about commercial flat roofs, we never use PVC - too much expansion potential. All our rooftop conduit runs here in the Albany, NY area are RMC of the galvanized type, and of course, threaded. There are standard plumbing supports with rollers, as well as standard expansion fittings (be sure to match the fitting to the conduit - don't use EMT with RMC unless approved by the manufacturer). A great product we have recently begun using is a EPDM pipe support by the Rubber Triangle Company that is compatible with most rubber roofing, and allows a lot of movement. -Glenn From: [email protected] [mailto:[email protected]] On Behalf Of James Rudolph Sent: Thursday, December 22, 2011 9:39 AM To: RE-wrenches Subject: [RE-wrenches] Expansion on conduits on commercial roof tops! Howdy Wrenches, I was wondering how everybody is dealing with expanding conduits on roof tops? Do we have an accepted best practice on this?. What I am really looking for is a way to starp long conduit runs on commercial rooftops in direct sun that allow movement and expanision joints to do thier job. Mahalo in advance! James B Rudolph NABCEP Certified PV Installer
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