<div dir="ltr"><div>I design a lot of grid tied projects, but I still do a rooftop about once or twice a year. All of them going back 7 years or so always used covered/vented cable tray. This includes homeruns, DC feeders, and all AC wiring. There still is some metallic conduit used (usually EMT) - a small jumper for a single wire, or the 3'-5' jump from the cable tray to the inverter or panelboard, or a single circuit output. Cable tray is a lot more cost effective and it has thermal expansion inherently built in so there's less concern about separation. You can also fill up a smaller area than conduit so it's a bit easier to walk around, although we have to install some stairs to go over some of the more crowded spots.</div><div><br></div><div>It gets a little complicated and labeling is incredibly important as you don't want to mix DC and AC wires in the same tray, nor can you mix communication cables in it either. <br></div><div><br></div><div>I haven't done once under the Jan 1 2019 rapid shutdown clause yet nor do I see one on the horizon anytime soon but I see no reason why cable tray still won't be used.<br></div><div><br></div><br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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Date: Sat, 25 Jul 2020 01:00:03 -0500<br>
From: Corey Shalanski <<a href="mailto:coresolar@gmail.com" target="_blank">coresolar@gmail.com</a>><br>
To: <a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">re-wrenches@lists.re-wrenches.org</a><br>
Subject: [RE-wrenches] Rooftop Conduit<br>
Message-ID:<br>
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<br>
Wrenches,<br>
<br>
I noticed a couple good threads ("Cable tray" / "PV Wiring methods") about<br>
this topic back in 2013, but I haven't seen much discussion since then.<br>
Given some of the advances in PV equipment since then (improved<br>
ground-fault protection, arc-fault circuit protection, rapid shutdown), I<br>
am curious about current attitudes toward using metallic conduit/cable tray<br>
on rooftops. I am primarily interested in hearing about flat commercial<br>
rooftops but imagine some of the same conventions may apply for residential<br>
rooftops.<br>
<br>
What are you using for long (or short) dc circuit runs on rooftops? Is<br>
cable tray still considered safer? Are there situations where conduit may<br>
be merited? If so, is RMC favored over EMT?<br>
<br>
Do best practices change when considering ac circuits (rather than dc)?<br>
<br>
Back in 2013 Bill Brooks said that PV installers are the "crazy people"<br>
installing conduit on rooftops, and he prophesied that using cable tray on<br>
roofs would "become common practice soon." Where do we stand now?<br>
<br>
--<br>
Corey Shalanski<br>
Jah Light Solar<br>
Portland, Jamaica<br>
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