Mounting solar panels

Topic: Mounting solar panels (Read 743 times) previous topic - next topic

Mounting solar panels

August 28, 2015, 09:42:54 am

I have three large solar panels(125 watts each) that I want to mount on the roof of my U320. I want to mount them using a four-point anchor system for each one. I would appreciate any suggestions as to the ideal procedure to bolt the mounts to the roof.

Thanks,
Mike

Re: Mounting solar panels

Reply #1 – August 28, 2015, 09:54:40 am

Mike,

I have a appointment next month to get a solar system installed on our coach. The shop is well known for doing quality installations. One of their trademarks is using a non-invasive panel mounting system. They bond the brackets to the roof using a high-tech adhesive. They supposedly have had excellent success with this method. You might check out their web site for some ideas:

Welcome to AM Solar_Your RV Solar Specialists since 1987

Re: Mounting solar panels

Reply #2 – August 28, 2015, 09:59:37 am

That the same folks who put 1200 watts on the roof of our 1999 U320 40 footer.

AM Solar is a class outfit.

They installed it and I haven't had to change a setting yet.

BTW, our 1999 U320 is still for sale. See it at Bernd's shop on Main St in Nac.

best, paul

Re: Mounting solar panels

Reply #3 – August 28, 2015, 10:19:31 am

They also did the initial install of my first panels and controller. as Paul said-class. My panels are bonded on with VHB tape as well and have not moved in over 3 yrs. This is not a problem to holding them on roof.
JohnH

Re: Mounting solar panels

Reply #4 – August 28, 2015, 11:18:31 am

Kind of hard to see, but mine are bonded down.

Re: Mounting solar panels

Reply #5 – August 28, 2015, 11:39:48 am

Andy,

That is a VERY nice, clean looking installation! I especially like the clear "walkway" down the center of the roof. I hope ours comes out looking that good! I'm going to show that photo to AM Solar when I get there. What is the total wattage of your system?

Re: Mounting solar panels

Reply #6 – August 28, 2015, 11:55:35 am

I have two, 240-watt, panels bonded to the roof on stand-offs. They sit about 1.5 inches off the rooftop and actually shade the roof (and help keep the rig cool in hot sun). I used 3M VHB tape from Amazon for this.

The first thing I did was to attach the stand-offs to the panels. These are available at several places. Since I originally wanted to be able to tilt the panels (and might, still - although I never have) I have all the gear for this bought from AMSolar's Internet site.

I had already figured out the panel positions by cutting one of the cardboard boxes they came in to the exact size of the panel and arranged them on the rooftop to determine exactly where and in what position the panels will be installed. Once this was established I put the panels on the rooftop and laid them out the way I wanted and marked the locations where the bottom of the stand-offs will be glued down with a pencil.

Then I moved the panels slightly and cleaned the fiberglass rooftop well before the installation using a mildly abrasive cleaner to make sure that all the dirt, wax and film is off and I was down to the gelcoat. After that cleaner was wiped off (using clean-but-old tee shirts) I used acetone to clean off each of the areas and the bottom of the metal standoffs (about 1" square).

Once everything was clean I cut the VHB tape into appropriately sized squares and uncovered one side of the double-backed tape square and lifted the panels and stuck the tape down and then pushed down on the panel to help it bond. I did all 4 stand-offs this way.

Then the DW and I loosened the stand-offs very slightly so that they would better conform to the rooftop once the panels were completely secured to the fiberglass and then carefully positioned each panel where it was supposed to go and then lifted the panel enough to peel off the bottom protecting plastic of the VHB square and pushed the panel into place. If you loosen the stand-off fasteners too much they'll move too much so this is kind of a fine line.

Once the stand-offs were all pressed down we added a few weights to each corner to keep them pressed down and let them sit that way for a few days.

Once I was pretty sure they had bonded I took the weights off and tightened the fasteners holding the stand-offs to the panel frame. Then I started wiring it up. The two panels are in series and those, in turn, are in series with two 12v (nominal) flexible panels (Unisolar 69-watt). The Unisolars are rated as 12vdc and 4-amps while the solid panels are rated at 24vdc and 8-amps. The two flexible Unisolar panels will handle the 8-amps of current flow in the circuit and add 12vdc to the aggegate going down through the Midnite Solar circuit breakers and into the Midnite Solar Classic 150 charge controller.

We've put about 4,000 miles on this installation and, to my complete surprise, they're still up and bonded well to the rooftop. This only works on fiberglass roofs (or steel or aluminum - probably). Certainly no regrets on this installation. My complete costs for the entire system (including the expensive charge controller) were under $2000; 640-watts total.

I have a scaffold that is ten feet long and five feet wide and one section (six feet) is perfect. I usually stood on the scaffold while the DW (13 years younger than I am) was on the rooftop.

The Unisolar panels were put down because they can be walked (gently) upon and I wanted to retain access to the rooftop without removing panels.

Hope this helps you figure it out.

Craig

Re: Mounting solar panels

Reply #7 – August 28, 2015, 02:40:02 pm

Chuck, really no need to show picture as that is the way they do them all. Mine is mounted same way. The Tech lays out cardboard the same size first as did Craig and makes sure there will not be any shadows etc. I have added more panels but still keeping the same footprint.
JohnH

Re: Mounting solar panels

Reply #8 – August 28, 2015, 02:44:27 pm

I have five 240 watt solar panels, which are attached with stainless metal screws put into the aluminum roof trusses. I was not comfortable with using double sided tape because I have seen car side trim come loose after a few years. I do suspect that trim coming loose was caused by double sided tape being placed on waxy or dirty surface, but I am not certain. I also have three 55 watt panels, so my roof is more covered than the picture in this topic. My panels are mounted such that they can be tipped up, which is done a couple times a year for applying wax.

Re: Mounting solar panels

Reply #9 – August 28, 2015, 03:26:53 pm

wa_desert_rat
It appears that you have mixed nominal 12v panels (paired) with nominal 24v panels. While this will work, you are probably not getting the maximum wattage from all your panels. If there were a controller which had more than one set of PV connections, then panels with different ratings could be used without loosing capacity. I do not know of one.

I will attempt to describe the issue I am referring to in this paragraph. There are nominal 12 volt panels which have an Open Circuit Voltage (VOC) of 38 volts (or higher), but most are VOC 21 volts, and the lowest I have seen is VOC 18 volts. The VOC 18 volt panels were intended to be used for a trickle charge without a controller. Mixing VOC 21v with VOC 18v will work, however, the VOC 18v panels will provide very little wattage because they will be over powered by the VOC 21v panels. Mixing VOC 38v with VOC 18v will result in the VOC 18v providing NOTHING. What makes this more complicated is that each panel has a unique voltage at which it will provide the maximum wattage. Maximum wattage is what MPPT controllers attempt to provide, and can only provide if all panels have the same MPPT voltage. My panels are VOC 38v and MPPT 28v, so I have 28 volts coming off the roof going to the Outback 80amp controller. I also have three 55watt, VOC 21v, with separate wiring coming off the roof, which runs at whatever voltage the load dictates (load is my car battery, or the Koolamatic ceiling fan, or my golf cart batteries).

Re: Mounting solar panels

Reply #10 – August 28, 2015, 03:39:50 pm

Quote from: John Haygarth – August 28, 2015, 02:40:02 pm

Chuck, really no need to show picture as that is the way they do them all.

I commented on Andy's photo for two reasons: the clean, neat routing of the wiring, and the fact that full length roof access was allowed for. I have seen (photos of) many panel installations where these design factors were not evident. In some cases, the wiring is run haphazardly in all directions and is only loosely secured - looks like a nest of worms. In other cases, there are too many panels in too small a area, resulting in a mine field if you tried to walk on the roof. I am sure any truly professional installation would not exhibit these flaws, but I also feel it never hurts to have what one considers a "good example" handy for quick reference.

Re: Mounting solar panels

Reply #11 – August 28, 2015, 04:24:46 pm

Here is our installation from several years ago. Four 280 watt Yingli commercial panels for 1140 potential. Working well today. Used screws into roof sealed with GE Silicone II.

Photos by E Pierce Stewart Jr - Google Photos

Pierce

Re: Mounting solar panels

Reply #12 – August 28, 2015, 04:41:03 pm

Chuck, I was not discounting the idea just that they (Amsolar) do great installs each time. I actually made some aluminum deflectors for each row of panels so there is very little wind pressure hitting the ends of them as we travel. I also put "levelling caulk" around each mounting brkt to give extra assurances.
JohnH

Re: Mounting solar panels

Reply #13 – August 28, 2015, 04:53:07 pm

OK, here's a question for those of you who live with solar panels on a daily basis: what is your recommended procedure for keeping the panels clean? Our coach (unfortunately) when not on the road is parked in our driveway, totally out in the open in dusty, windy West Texas. We don't have a RV garage, storage building...not even a simple cover, and won't have one until we leave this house and move on to the next one (hopefully in the not-too-distant future). I anticipate a rapid build-up of dirt, sand and dust on our (future) panels. What can I do to clean the panels without damaging them? For me, climbing up on the roof is no problem (at least for now...knock on wood).

Re: Mounting solar panels

Reply #14 – August 28, 2015, 05:00:35 pm

Chuck I have 5 100 watt panels on the roof, The PO got them from the place in Oregon As far as cleaning them When I wash the roof I just wash them as well, I have not seen a lot of dirt built up at all.

Re: Mounting solar panels

Reply #15 – August 28, 2015, 05:08:35 pm

I just hose ours off. Could use a pressure washer to take the dirt film off. At our latitude, we get about 600 watts a couple of hours after the sun comes up in the summer. January in Quartzsite saw about 580 watts max with dirty panels. This is with the panels flat. The output goes way up with them oriented toward the sun but our 1140 watt potential is overkill so don't worry about tilting or keeping them really clean. Retrofitting LEDs and using a LED TV really cuts down on the battery drain and the controller goes to float after a couple of hours each morning.

Pierce

Re: Mounting solar panels

Reply #16 – August 28, 2015, 05:10:55 pm

So the panel innards are pretty well sealed against water intrusion?

Re: Mounting solar panels

Reply #17 – August 28, 2015, 05:38:31 pm

Yes, well sealed. When you turn them over, you can see exactly how they are made. They have to stand up to a lot of exposure to the elements in solar farms.

P

Re: Mounting solar panels

Reply #18 – August 28, 2015, 07:27:23 pm

Chuck, I use a mild solution of windex with a microfiber rag.

Re: Mounting solar panels

Reply #19 – August 28, 2015, 07:42:29 pm

In 3 + yrs I have never cleaned them and my batteries are full up evry day. Driving in rain helps so go visit someone in Washington State or Vancouver!! We do not get rain here so that is why we go down to mexico each year as we pass thru wet weather.
JohnH

Re: Mounting solar panels

Reply #20 – August 28, 2015, 08:56:33 pm

We just spray ours down with water before a trip. Nothing high pressure, just a nozzle on a garden hose. In a land of hard water we have managed to be on the only well in the county that's actually soft water. Lucky us.

Craig

Re: Mounting solar panels

Reply #21 – August 28, 2015, 10:06:19 pm

Many coaches use tape, but we are not believers to trust tape to work on our painted roof. We figured it would just pull the paint off the gelcoat.
We did not want to drill our 4 135-watt & 2 100-watt panels, and we only wanted to screw panels down into the metal cross beam roof supports. Since the panel holes did not match the roof beams, we used double aluminum angles. One angle to panel pre-drilled holes, another angle drilled and screwed into roof supports, with both angles bolted together. Been using our mounting method for 20 years.

Re: Mounting solar panels

Reply #22 – August 29, 2015, 10:35:03 am

Thanks Everyone. Some great ideas and installation guides. Believe I can do this job with the info here.

Mike

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