Fasteners for mounting solar panels

[Big-B]

I'm getting ready to mound a couple of 280 watt panels on the roof of our 34 foot Bighorn 5th wheel. I'm using a couple of 10 foot lengths of unistrut to mount them on and am wondering what kind of fasteners to use to mount the unistrut. I'm planning on using 1/4" stainless steel lag screws and hopefully hit the trusses or rafters in the process. Does this sound like a good plan and what kind of fasteners should I use?

If the roof on my Bighorn is the same as the one that I saw in another post it looks like it only has 3/16 wood on top of styrofoam.

 

[SLO]

I used these.

https://amsolar.com/rv-mounting-accessories/91m-35ms

Didn’t bother looking for trusses, just screwed into roof. Then put enough Decor self leveling caulk to completely cover screws and brackets. After 5 years and one trip to Alaska, no movement or leaks. My panels were 100 watts so a little bit lighter, 16.5 lbs. The brackets are very expensive, for 6 panels, but all metal is SS and no rust at all in 5 years. My experience, for what it’s worth.


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[jbeletti]

I used stainless steel lag bolts. Can't remember the diameter - probably 1/4".

• I pre-drilled the holes in the plywood with a smaller drill bit (probably 1/8")
• I put butyl tape under each panel bracket where it would lie on the roof
• I slowly installed the lag bolts through the panel brackets and into the roof
• I used Dicor lap sealant to completely cover the lag bolt head and the entire panel bracket foot (about 1 square inch)

I suggest you use butyl tape on whatever part of your system (UniStrut) will contact the roof membrane where a fastener will be going through it. Then of course - lots of Dicor lap sealant.

 

[Big-B]

Thanks for the quick responses. I think tomorrow I'll pick up some of the tape for under the unistruts. I already have a tube of dicor and plan to drill a 1/8" hole in 5 places, then give each hole a nice shot of Dicor and put the lag bolts in. I have 1" lags and they will be about 3/4" into the roof which I would think will be plenty if the wood on the roof is as thin as I've read at 3/16".

 

[jbeletti]

Thanks for the quick responses. I think tomorrow I'll pick up some of the tape for under the unistruts. I already have a tube of dicor and plan to drill a 1/8" hole in 5 places, then give each hole a nice shot of Dicor and put the lag bolts in. I have 1" lags and they will be about 3/4" into the roof which I would think will be plenty if the wood on the roof is as thin as I've read at 3/16".

Sounds like a perfect plan to me.

 

[Big-B]

Sounds like a perfect plan to me.

Thanks Jim. I should have 560 watts of solar panels mounted this week while it's still warm here in Michigan. Possibly mounting another two of the same panels on the front later.

 

[jbeletti]

Thanks Jim. I should have 560 watts of solar panels mounted this week while it's still warm here in Michigan. Possibly mounting another two of the same panels on the front later.

You’ll never regret putting too much solar on the roof. I have 1080 watts. Would like a couple hundred more but I’m out of roof space.


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[marknewbill]

It am pretty certain the answer is no, but is there yet any solar system that can run the AC unit yet, that would be great!

 

[Oregon_Camper]

It am pretty certain the answer is no, but is there yet any solar system that can run the AC unit yet, that would be great!

Solar will never directly run AC unit, as they require A/C power not D/C power. You can ( and I do) run your AC unit from battery bank, however you need to be prepared to drop ~$10k to get this working. ~1,500watt of Solar panels, 3000w inverter, large battery bank (~600Ahr of Lithium works great) and all of that installed. Might save ~$2k if you can do the install yourself.

 

[marknewbill]

Solar will never directly run AC unit, as they require A/C power not D/C power. You can ( and I do) run your AC unit from battery bank, however you need to be prepared to drop ~$10k to get this working. ~1,500watt of Solar panels, 3000w inverter, large battery bank (~600Ahr of Lithium works great) and all of that installed. Might save ~$2k if you can do the install yourself.

Thats interesting, so how long will your setup operate the AC unit provided you had full sun, do you get a couple hours of use? or will it run all day or how does that look. I know it will matter how hot it is, so lets assume it it running full power all the time and never catches up.
Thanks,

 

[porthole]

I used these.

https://amsolar.com/rv-mounting-accessories/91m-35ms

Boy did those brackets get pricey. When I ordered my panels those were just coming out and my vendor sent me 9 sets after the panels were sent at no charge.

 

[Oregon_Camper]

Thats interesting, so how long will your setup operate the AC unit provided you had full sun, do you get a couple hours of use? or will it run all day or how does that look. I know it will matter how hot it is, so lets assume it it running full power all the time and never catches up.
Thanks,

Great timing. I was playing with this yesterday and when I was running the bedroom AC unit, I was pulling a WHOPPING 165 amps. That means I could run the AC unit for about 3.5 hours on my 600Ahr of Lithium batteries (6x100). Now, I have nowhere near enough solar on the roof of our Bighorn (now at 600w) to keep up with the AC usage, but here in Oregon, we don't have a need to run the AC unit so it has been a moot point for our needs. Worse case I can fire up my portable Yamaha generator and then use both battery power and gen power to get more AC run time.

Battle Born just today announced their Summer sale, so they are starting at $100 off and some are even more than that. Here is a link. FYI...I am an affiliate with Battle Born.

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At Battle Born Batteries, we specialize in top of the line LiFePO4 lithium-ion batteries. Get out there, stay out there!

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[marknewbill]

Great timing. I was playing with this yesterday and when I was running the bedroom AC unit, I was pulling a WHOPPING 165 amps. That means I could run the AC unit for about 3.5 hours on my 600Ahr of Lithium batteries (6x100). Now, I have nowhere near enough solar on the roof of our Bighorn (now at 600w) to keep up with the AC usage, but here in Oregon, we don't have a need to run the AC unit so it has been a moot point for our needs. Worse case I can fire up my portable Yamaha generator and then use both battery power and gen power to get more AC run time.

Battle Born just today announced their Summer sale, so they are starting at $100 off and some are even more than that. Here is a link. FYI...I am an affiliate with Battle Born.

Battle Born Batteries | Reliable Lithium-Ion Batteries

At Battle Born Batteries, we specialize in top of the line LiFePO4 lithium-ion batteries. Get out there, stay out there!

battlebornbatteries.com

thanks for the info. thats really pretty good info there. for me in the south the ac is mandatory. hopefully one day the tech improves so you can run the ac all the time. maybe someone will make a dc air conditioner like they make the dc fridges now.

 

[AidanMoran]

Hope your project turned out well, and I'd love to hear an update if you have one!

 

[AidanMoran]

Oh...even though your post is from 2020, I bet there are people (myself included) who still find this topic relevant. Mounting solar panels on a 5th wheel is an awesome project, and your idea of using 1/4" stainless steel lag screws sounds like a sturdy choice, especially if you can hit the trusses.

 

[Big-B]

I typed up a long reply yesterday but for some reason it isn't here. Bottom line is it works great. I added a third 280 watt panel so now have 840 watts of solar and a 2,800 watt Magnum inverter. I took the advice of one of our other members and put down a strip of dicor tape and then put the Unistrut down and lagged them down and covered the lag bolts with Dicor out of a tube. I only hit a couple of trusses but I've put easily over 10,000 miles on it with no problems. It's super nice to just push a button and have power to the whole 5th wheel. This fall before we head to Arizona I'm going to put lifepo4 batteries in it. If you have any specific questions I'll try to answer them.