Solar PV Inspection Walkthrough - Wiring Methods (5 of 8)

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This video is number five of an eight-part series about the electrical inspection of a roof-mounted photovoltaic system.
This series is not meant to cover every aspect of an electrical inspection of a solar or photovoltaic system, but to instead introduce the viewer to some of the things an electrical inspector might be looking for when he or she is on-site.
This video was produced by the Northern Mid-Atlantic Solar Education and Resource Center, part of The Pennsylvania State University. You can learn more at www.solarcenter...

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@benbarbre4347 9 жыл бұрын

What did they use to seal that pipe up with? Looks like expanding foam

@pennstatesolarcenter4117 9 жыл бұрын

Ben Barbre Ben, thanks for the question. It is in fact an expanding foam in the sense that it expands and is a foam, but it's not the same stuff you might use to insulate a small space in your home (like Great Stuff, or other brands of spray foam insulation). We're not sure what the exact product used here is, but it's specific to this use -- filling conduit around wire without degrading the wire insulation and without adversely affecting the thermal conditions (which are tied back to the fill ratio of the conduit, number of wires, size of wire, conditions of use, etc). The purpose of using it is to seal rather than insulate, as protection from vermin, insects, and water. There are a number of products that fit the bill here -- Polywater's duct seal and Ductolox are two that come to mind. www.polywater.com/ductseal.html www.arjunox.com/ You generally put in some type of "stopper" or damming strip a certain distance into the conduit and another in front and then use a nozzle to insert the foam between the two dams. There are also putty-type products on the market. As always, talk to your electrical inspector!

@benbarbre4347 9 жыл бұрын

Penn State Solar Center Thanks, the links you posted are interesting. I cut out a rubber gasket from a toilet stop, put 3 holes in it for the wire coming from the pv array into the junction box and screwed a flex pipe connector over it. I'll stick this in there on top for good measure. I have a single array of 10 panels, 255w ea no combiner- just a shot through emt to the dc disconnect > inverter. But this even stumped the electrician over at the distributor. We agreed though, either run into the junction and then something like flex pipe up and around so water doesn't get in, or rubber stopper. One of the contractors said they fill up with water anyway but I won't accept that :) Most contractors noticed don't know anything about solar. Even at the permit office there's one senior inspector that does all the solar that comes through. If he's not there, you get a bunch of blank faces when go into the dc side of things. The inspector I had didn't check the junction. I'll foam it on top of the rubber stopper for good measure and stick another rubber stop over that. So you don't recommend the expanding foam they sell locally? We have a distributor here that sells most of the stuff on the wiring end. Like I said, all I have are pictures of professional installs and in a lot of those, nothing is there it's just open under the array going into the junction > combiners. I like that use-2 is waterproof, but there really shouldn't be water capable of getting in like you said. I'll pick up some foam :D I saw the foam in the riser had to replace too. Guess the electrician got all crazy there but when opened up the meter there was foam all up in the pipe.

@pennstatesolarcenter4117 9 жыл бұрын

Ben Barbre I can't speak to your particular situation, of course. The code articles that are often mentioned in regard to this are 2011 NEC 225.27, 230.8, and 300.5(G) which all effectively say the same thing. The key phrasing, from 225.27 in this case, is "Sealants shall be identified for use with the cable insulation, shield, or other components." BUT those code articles all reference "where a raceway enters a building or structure from an underground distribution system," which isn't necessarily what we're talking about. However, assuming that these are indeed the correct code articles, the type of spray foam insulation you can pick up at a local hardware store isn't identified for this use, so it would not meet the requirements. I can imagine it can get confusing, as many of those products (fire block, for instance) can be used on the outside of conduit or around romex cable. I'm not familiar enough with the chemistry at work here, but several sources (answers.angieslist.com/Can-I-spray-foam-insulate-conduit-openings-service-panels-q105657.aspx for example) claim that something like Great Stuff will degrade the insulation on the wire. Similar language is found inside some of the marketing and technical materials from a product like Polywater's FST Foam Sealant. For example, the technical data sheet (www.polywater.com/fstspec.pdf) says "Compatible with common cable and wire jackets," implying that other products are not, and there's a whole section in their Tech Talk publication called "Cable Compatibility" (www.polywater.com/techtalk-vol1.html) that continues to talk about how their product IS compatible with common cable jacket materials (like USE-2), but not necessarily why other products aren't. They also specifically speak to duct putty and canned foam not meeting the NEC requirements, though again they're referring to code articles that may or may not apply in the case of DC conductors entering a conduit at an array. I don't doubt there are numerous installations out there that have passed inspection that don't have any sealant. I also don't doubt that the FST stuff we've been talking about is pricey enough to scare people away (though don't quote me -- I haven't looked). However, I have seen numerous pictures of bees and rodents that have taken up residence in j-boxes and combiner boxes. It's nice and warm in there, and everything can be fine until one leg touches positive and the other leg touches negative. One of the links I posted here (the Angie's List one) proposes other solutions. If you're taking only a few wires in, you can use strain reliefs. I'm sure if you look around you'll find a lot more solutions, though I had a little trouble finding much while writing this. Good luck!

@benbarbre4347 9 жыл бұрын

Penn State Solar Center Thanks, on my way to check out what they have down at the warehouse. I'll definitely get the right stuff. That duct putty is a mess, the foams like you linked seem to be the way to go. Interesting how they aren't all compatible. I would have thought the cheap stuff would be fine. Thanks again, you don't need luck when you have smart people to consult :) I found the idea to loop up using flex before the junction here /watch?v=W8N5iN_aRXs&t=12m28s If I read the green NEC rule book again, going to have a headache.