OnTheRidge

Solar Panel Installation

7 posts in this topic

I am planning to install two 130 watt panels on the RV roof.

The kit came with fasteners that will mount the unit flush on the roof with no space ( 1/4" at best) below the panel.

Various articles suggest you need a 2 inch+ space to allow for airflow underneath the panel to keep it cool.

Can anyone provide some advice on the best practice for mounting?

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Most high efficiency panels will get warm; partly from the sun's infrared radiation, and partly from generating current in the panels substrate. For most you need air circulation all around the panel.

That said, their are some panels that don't generate much heat or transfer much solar heat to the backing material. Presumably, if the manufacturer says zero clearance required, then that's the case.

But anything I mount on the roof with zero clearance has a healthy bead of Dicor self-leveling sealant under and around it. Regardless of the type material composing the roof seal, you don't want standing water captured under anything that will lead to corrosion and mildew. And a dirt catch that will cause side wall streaks with moisture.

With metal frame panels, "S bracket" mounts are best. Particularly if your roof is not perfectly flat. Then again, some panels flex and cannot use the S bracket type of mount.

Call the manufacturer and voice your concerns. Many times a telephone call to customer service makes a lot of difference.

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I had two 110 watt panels on my last coach and now have four 125 watt panels on this coach. Each system had maybe 3/4" between the panel and the roof. However, the panel itself is recessed within the frame to allow for the electrical connection box so in reality the actual panel is probably 2" up from the roof while only the frame is 3/4". I've never had any issues with heat and find that most heat is reflected and on the top surface of the panel, not the bottom.

I used fixed aluminum angle iron mounts designed for the panels. I used 3/16" stainless steel rivets to mount them to the roof rather than screws. I just don't have much faith in screws not pulling out and tearing the threads whereas the rivets knob up on the backside of the roof and hold very well. Be sure to apply self-leveling sealant beneath the mounting pads as well as all over the top of them to prevent any leaks.

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We had six panels (4 80s and two 125s) on the roof of our trawler, a very similar installation to any RV, but bigger. We used custom-fabricated omega mounts (similar to s-mounts but stronger) that held the panels off the roof for ventilation (per manufacturer's recommendation). We used self tappers but the recommendation elsewhere in this site to use rivets sounds good. If you have a fibreglass roof (as we did) then use 3M 5200 or similar adhesive bedding/sealing compound under the mounts, not self levelling compound. Self levelling compound is not an adhesive. We also put self levelling compound right over the mounts, perhaps not needed with the 5200 but why risk a leak! We never had a moment's trouble with this installation, despite going through some heavy gales and taking sea water right over the boat on several occasions.

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3M-5200 is some awesome stuff. BUT don't use it if you ever want whatever your mounting to come off. It will not and will take part of the substrate with it if you force it off. If you want it to come off later better to use 3M-3600. It is almost the same great formula but more flexible and will come off later if you need it to. Both are great sealers and adhesives and I have used both on all my stuff from kayaks to sailboats to motor-homes with great success. NEVER use silicone for a sealant/adhesive. It will work for awhile but is guaranteed to leak later on and then the silicone has penetrated into what ever you put it on and nothing else will stick to it, including more silicone. Butyl caulking is better as a sealant.

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Completely agree on NOT using 5200 on anything that has any potential for ever having to be removed.

I use 3M 4200 instead.

Brett

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The installation instructions for my panels specifically require a ventilation gap underneath. If you drive around and look at the big multi-kilowatt installations on home roofs, you'll find that every installation of crystalline silicon panels has a substantial spacing from the roof. As others have pointed out,some thin-film panels are designed for installation in contact with the mounting surface.

Some details and photos of my installation are at http://www.damouth.org/RVStuff/SolarInstall.shtml.

If I'm boondocking in the same place for a few days, I tilt my panels up to maximize output. In winter, this can increase output by 40%. But on a windy day, the tilted panels are pushed pretty hard by the wind. So I made sure the attachment to the roof was very secure - see details on the website.

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