This details the steps I went through for mounting my Mission Solar 320 watt panels to the roof of my RV trailer. While there are multiple methods to secure a panel to an RV roof, this focuses on using standard Z brackets. Other methods include DIY brackets, Unistrut, adhesive tape and all the other third party mounting methods. I went with the Z brackets because they were simple and lightweight.
I am highly skeptical of the adhesive-only mounting method on an EPDM roof. In my opinion, you are setting yourself up for catastrophic failure if you try to secure rigid PV panels to an EPDM roof with only adhesive tape. Flexible PV panels that have no air gap are a different issue and adhesive-only mounting should work OK there.
Step 1: Measure The Roof
Measure the roof of the RV, including all the objects mounted on the roof. I used the CAD application Sketchup to draw everything out.
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The advantage of the CAD tool was that I could draw my solar panels to the correct dimensions and then place them on the roof. This was a huge benefit as I had originally intended to go with four 200 watt panels. Arranging them on the roof showed that they weren't going to fit. That prompted me to change to a completely different panel setup and I went with two 320 watt panels from Mission Solar instead.
The big mistake I made with this is that I forgot to include the Z brackets in the footprint of the panels on the roof. Fortunately, when it came time to do the install I had a few inches to play with and it turned out OK.
While looking at the placement of the panels on your drawn roof, consider how existing objects could throw shade on the panels. Placing the panels near the air conditioning unit is likely to result in some shade on the panels for a few hours a day.
Here's what the target area of my roof looked liked before I got started.
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Step 2: Verify The Integrity Of The Roof
Is your roof in good shape? Have you actually checked every inch of the target area? You need to look for tears, holes, cuts and soft spots in the EPDM (rubber) roof material. Any flaw needs to be addressed now. You CANNOT get to anything under the panel once the panel is installed.
My roof turned out to NOT be in good shape. In fact, it was so bad it was like bouncing a small object on a trampoline. Here's what I found when I pulled back the EPDM.
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Fixing the water damage was not optional. It HAD to be done because one of the Z brackets needed to be placed right in the middle of all the damage. I removed as much rotted wood as possible and replaced it with like material. I also put as much new insulation in as possible.
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This is the last photo before I applied butyl tape to the edges and glued the EPDM back down using a Dicor adhesive. It took a couple hours to clean all the rotted wood from the EPDM. This was a five day project, with a pause of two days waiting for the adhesive to be delivered. I got lucky that the damage was at a corner. If this was in the middle it would have been a much longer and difficult job.
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Step 3: Find your Roof Trusses
If your trailer has roof trusses, like mine did, you need to find them. This is what you want to secure your Z brackets into. Finding the trusses is a bit like an Easter Egg hunt. Here are the techniques I used.
A. Stud Finder - I was using a 20+ year old Zircon Stud Finder at first and getting random results. I upgraded to a Zircon 900c stud finder and got better - but not perfect - results. The stud finder would find a truss going one way, but not the other way. It was quite frustrating, but I ran it enough times to verify the results in multiple locations. If you're getting lousy results using the stud finder on the roof, go inside the trailer and use it on the ceiling.
B. Thump Method - Using the butt end of a large screwdriver I thumped the roof and listened for hollow and solid sounds. This was a fairly good method.
C. Tape Measure - My trusses were
usually located on 16" centers. This wasn't always the case, such as when the 16" mark was right in the middle of a vent. This caused the installer to shift the truss forward a few inches.
D. Open the Ceiling - Since a roof vent was in the right position, I opened the vent mount from the inside of the trailer. That gave me easy access to the "attic". From there I could see the trusses that were forward and backward from the vent. With attic access I was also able to stick my tape measure in and measure to the next truss.
Using all four methods, I was able to accurately map out the locations of my trusses. In the first photo in the thread you can see blue tape on the roof. I used the tape to mark the location of the trusses. All my Z brackets have at least one screw in a truss. Due to the width of the truss - usually no more than 1.5" - one screw in a truss per bracket is about all you'll get. I would rather get one screw solidly in the middle of a truss, than two screws on the edge of a truss.
Step 4: Remove Obstructions
As you can see in the first photo of the thread, there was a roof rack right in the way of my target location. That had to come out. I considered trying to mount the panels to the rack, but it wasn't that secure and I needed the entire space. I had to seal the holes where the rack was screwed into the roof.
Step 5: Prepare The Roof
If you need to clean and seal the roof, do it now. I added a few Eternabond patches in locations that had cuts. I removed and replaced the Dicor Lap Sealant on the rear edge of the trailer. These are things that are very difficult to do once the panels are in place.
Step 6: Install The Z brackets On The PV Panels
Using your carefully calculated measurements, figure out where on the panel the brackets need to be placed. Don't assume that you have to use the existing holes in the panel's frame. I drilled seven new holes in each side of the panel's frame. I used three brackets on each side instead of the more common two on each side. I did this for two reasons. First, the forward and rearward brackets needed to be moved closer to the front and back of the panel to be on the truss. Second, because of the longer distance between the brackets, I felt the need to support the middle of the panel better.
Should you need to drill new holes in the panel's frame, be sure you place a block of wood or other suitable material that will "catch" the drill bit when it comes through the aluminum frame. That last thing you want to do is nick or drill into the back of the panel.
The Rich Solar bracket kits I bought came with bolts, washers and nuts. I chose to toss the nuts and use my own nylon lock nuts. If I had used the provided nuts I would have added some blue Loctite.
Do the bracket install on the ground. It's going to take a while. A socket wrench and a box end wrench will make the tightening of the bolts go a lot faster. Get the nuts snug, but don't overtighten.
Which way do the brackets go? In the picture below you can see there is a slot end and a two-hole end. I chose to mount the two-hole end on the panel frame. My thinking on this is that I wanted the flexibility of placing the roof screw anywhere in the bracket so I could hit the truss exactly. The two-hole end didn't give me that flexibility.
A comment on bracket color: The chance that anyone is going to see the brackets is low. Just because your panel frames are black, doesn't mean you need matching black brackets. Had I realized how hidden the brackets are, I would have gone with a plain aluminum colored bracket. I may be the only one that knows my brackets are color coordinated.
Also in this step you need to prepare your supplies for the final installation.
A. Butyl Tape: I used 1" wide Butyl Tape, cut to match the length of the foot of the Z bracket. I cut the tape to length on the ground so I didn't have to do that on the RV roof. If you put the roll of Butyl Tape in the freezer or refrigerator it is a lot easier to work with. When it's hot it can be very messy. Leave the backing tape on for now.
B. Screws: I used #10 hex head sheet metal screws, 1.5" long. You shouldn't need a self-tapping screw, but that would be OK to use. I also used washers, which are probably optional.
C. Lap Sealant: I use Dicor Self-Leveling Lap Sealant. One tube should do the job for three panels if you're not too sloppy. Don't forget to take the caulk gun up. Bring a couple of rags for cleanup. Don't ever use silicone caulk on your trailer!
Step 7: Get The Panels On The Roof
I included this as a separate step for safety. My panels weigh 44 lbs each without any brackets and they measure 66"x40". They are very unwieldy. I put the side of my F-350 pickup as close to the rear of the trailer as I could. I tied rope to two of the brackets so I had something to grab. My wife and son - standing in the bed of the truck - lifted the panels to me on the roof.
Once you have the panel on the roof, be very careful with the brackets. They can be sharp enough to cut the EPDM. Avoid sliding the panel across the roof.
Continued in the next post due to the limit of 10 attached pictures per post and 10K character limit...
