What's the cheapest way I can mount 5 4x10 solar panels to my roof?

[Slippery]

I bought 5 4x10 Aquatherm panels used on craigslist for my above ground pool. They've been sitting on the ground all summer and have been doing fine for my 3000 gallon intex above ground. They only get about 4 hours of direct sunlight a day. But the roof get's far more direct sunlight. The weather has changed and I'd like to get the temps back up. My toddler gets super cold if the water isn't near 90 degrees.

I'd like to try DIY roof mounting them, but I don't know where to start.

I plan on getting a much larger above ground pool for next season so I want to design for that pool. I'm looking at

1​

5'x52" pools


roof closest to pool faces north (how much more heating would I get if I mounted on the south side?)

Can I buy and generic hardware to mount them to the roof or do I need the aquatherm branded ones?

Can I just screw the hardware in anywhere or do I need to find studs/rafters/joists?

How do I seal the holes I drill?

 

[mas985]

Welcome to the forum!

Are you still using the Intex pump that came with the pool? It may not work well with elevated panels. What type of pump were you planning for the new pool? How high is the roof?

Poking holes in the roof can be done but you need to be very careful to seal all the holes with roof mastic and also to inspect them annually.

If you can keep the panels on the ground, I think you are far better off. Plus, with 5-4x10 panels you shouldn't need much sunlight. I have 120 sq-ft of panels for a 20k pool and solar only runs about 1 hour per day when I use a cover and about 5 hours per day when I don't use a cover.

Are you currently running the panels and are they not producing enough heat? Are you using a cover to prevent heat loss?

 

[Dirk]

Mark - While it may be true that Slippery can get adequate heat by leaving them on the ground, that might not be true for other months. Putting them on the roof might extend his season some, if the roof offers better sun.

Issues of the pump aside, I'll share how I did it.

First off, I would not mess with DIY solutions for mounting. There are considerations beyond "getting them to stay up there." Some of those considerations are weight (they're full of water after all), expansion/contraction (both the panels and the pipes move around, all day, every day) and wind forces. Unless you know how to engineer for all that, I'd spend the extra dough and follow the manufacturer's instructions for mounting, including using their hardware. Which is exactly what I did. So far, so good.

Based on installation instructions provided me by the company that sold me my panels (who also install them), I screwed my panels' mounting brackets into the concrete tiles only. The screws do not penetrate the underlayment nor the wood deck. Seemed a little iffy to me, but that's how it's done in my area (which does get pretty good winds). Since the holes I drilled into the concrete do not penetrate the underlayment, I believe the roof is still sound, in terms of being water tight. I used a roof-grade sealant anyway, squirted into the hole before the screw went it, and afterwards to cover the screw head.

My panels along with their mounting system allow for expansion, and are rated for the weight of the panels and the forces of wind. Not hurricane wind, but typical wind (I forget what their rating is for that).

If you have a shingle roof, where penetration is required, that's another matter, one beyond my experience. The panel manufacture's installation instructions might cover that, and if they do, I'd follow their guide.

Wind force is the big deal, you have to account for that correctly.

 

[Poolzzz]

The Intex pump for a 3000 gal pool definitely won't work for roof panels. My 500 gph pump had a max head of about 7 feet. My 1000gph pump is probably bigger than yours and has maybe 10 feet at most. In any case it can't clear the air out of my 1.5 inch down pipe even at 5 feet. With these Intex pumps solar panels have to be ground level (below the water line) to work properly.

Regarding mounting on your north facing roof. ..don't bother...it won't work. Panels need to be south facing.

Do you have a bubble solar cover? Do you keep it on all times except for swimming? That makes a big difference.

When are you 4 hours of sun? If it's midday the extra sun hours may not be worth the effort. Especially in September when the sun is weaker and the warm sunny days fewer.

If you want to extend the season an actual heater works a lot better than solar panels around here. I suspect the same where you are.

 

[Vickery]

The cheapest way is to use nails. You want to put a lot of weight on top of the structure that your house requires to keep you dry and the walls erect? As a former general contractor that's like asking what's the cheapest used tires I could by for my wife or daughter's car. Asking that question with the follow up indicates to me that you would be well served by doing some research on solar cell placement, pump requirements, solar cell sizing needs and a bunch of other things. The previous responses are well supported. If you don't understand loads, structure, placement and sizing, this project is waaay beyond a diy project based upon a few questions here.

 

[Dirk]

The Intex pump for a 3000 gal pool definitely won't work for roof panels. My 500 gph pump had a max head of about 7 feet. My 1000gph pump is probably bigger than yours and has maybe 10 feet at most. In any case it can't clear the air out of my 1.5 inch down pipe even at 5 feet. With these Intex pumps solar panels have to be ground level (below the water line) to work properly.

Regarding mounting on your north facing roof. ..don't bother...it won't work. Panels need to be south facing.

Do you have a bubble solar cover? Do you keep it on all times except for swimming? That makes a big difference.

When are you 4 hours of sun? If it's midday the extra sun hours may not be worth the effort. Especially in September when the sun is weaker and the warm sunny days fewer.

If you want to extend the season an actual heater works a lot better than solar panels around here. I suspect the same where you are.

Yep, pump issues. Something to figure out. Bubble covers can make a huge difference in what you get out of a solar heater, for sure. I actually mounted my panels on the North side and they work great. I wanted to save the South side for PV solar. If works fine where I am because the sun is over head enough during swim season where north-south is same-same. Definitely makes a difference, though, in fringe months, where I'm finding what Poolzzz is claiming, not all that much benefit from solar for warming my pool in spring and fall. I think if my system was facing South, I'd get a bit of a bump, but probably not all that much. I'm sure my system is heating in the fringe season to some degree, but not my preferred degree!! Farther north where you guys are is another matter.

The cheapest way is to use nails. You want to put a lot of weight on top of the structure that your house requires to keep you dry and the walls erect? As a former general contractor that's like asking what's the cheapest used tires I could by for my wife or daughter's car. Asking that question with the follow up indicates to me that you would be well served by doing some research on solar cell placement, pump requirements, solar cell sizing needs and a bunch of other things. The previous responses are well supported. If you don't understand loads, structure, placement and sizing, this project is waaay beyond a diy project based upon a few questions here.

I can't argue that at all. And in fact I'm supporting Vickery's take with a part of my tale I only alluded to, and should have better explained. I did the whole install myself, but I have a local solar installer that sold me a kit. The kit included every single thing I needed, just as if they were doing the job themselves, along with the layout design for my roof, and they even provided a few "tech support" calls when I got stumped (how to screw the thing down properly was one of my calls). So, yah, I did it myself, but not really. I just executed the labor on a solar install designed by a reputable solar contractor. It's pretty simple work when you know what to do, but knowing what to do is the catch...

 

[jblizzle]

Note that these solar really do not weigh that much. They do not hold that much water and the weight is quite distributed. Standing on the roof is a much higher load.

 

[Dirk]

Note that these solar really do not weigh that much. They do not hold that much water and the weight is quite distributed. Standing on the roof is a much higher load.

I asked about that, and my system's designer said it was a non-issue on my house. Something about how all but the oldest of roof construction is over built and can easily withstand the additional load of PV or water-filled solar panels. They run the calc's when there is a permit involved, but the designer said the city never looks at them during planning review. Like I said, I think wind is the bigger issue. It's the pulling, not the pushing! Heliocol's are designed and mounted to account for high wind loads (a lot of the air passes right through them), but unless the OP understands what's involved with his particular panels, he could get in trouble with that aspect...

 

[jblizzle]

Absolutely. Heliocol panels are much more forgiving on the wind loads. So the mounting is much easier.

 

[Slippery]

Welcome to the forum!

Are you still using the Intex pump that came with the pool? It may not work well with elevated panels. What type of pump were you planning for the new pool? How high is the roof?

Poking holes in the roof can be done but you need to be very careful to seal all the holes with roof mastic and also to inspect them annually.

If you can keep the panels on the ground, I think you are far better off. Plus, with 5-4x10 panels you shouldn't need much sunlight. I have 120 sq-ft of panels for a 20k pool and solar only runs about 1 hour per day when I use a cover and about 5 hours per day when I don't use a cover.

Are you currently running the panels and are they not producing enough heat? Are you using a cover to prevent heat loss?

pump:intex 1000gph

no cover for my pool. I run the panels when ever there is direct sunlight on them (4 hours a day)

panels and cover: WOW. Do covers really save all that heat that you only need to run the panels one fifth of the time? Or is your cover the best cover made? Which cover do you have? What does it look like? WHat features does it have that makes it that effective. Do you keep the ocver on when heating?

I have the debris cover that came with the pool. Does that help keep heat in? I never use it

- - - Updated - - -

Mark - While it may be true that Slippery can get adequate heat by leaving them on the ground, that might not be true for other months. Putting them on the roof might extend his season some, if the roof offers better sun.

Issues of the pump aside, I'll share how I did it.

First off, I would not mess with DIY solutions for mounting. There are considerations beyond "getting them to stay up there." Some of those considerations are weight (they're full of water after all), expansion/contraction (both the panels and the pipes move around, all day, every day) and wind forces. Unless you know how to engineer for all that, I'd spend the extra dough and follow the manufacturer's instructions for mounting, including using their hardware. Which is exactly what I did. So far, so good.

Based on installation instructions provided me by the company that sold me my panels (who also install them), I screwed my panels' mounting brackets into the concrete tiles only. The screws do not penetrate the underlayment nor the wood deck. Seemed a little iffy to me, but that's how it's done in my area (which does get pretty good winds). Since the holes I drilled into the concrete do not penetrate the underlayment, I believe the roof is still sound, in terms of being water tight. I used a roof-grade sealant anyway, squirted into the hole before the screw went it, and afterwards to cover the screw head.

My panels along with their mounting system allow for expansion, and are rated for the weight of the panels and the forces of wind. Not hurricane wind, but typical wind (I forget what their rating is for that).

If you have a shingle roof, where penetration is required, that's another matter, one beyond my experience. The panel manufacture's installation instructions might cover that, and if they do, I'd follow their guide.

Wind force is the big deal, you have to account for that correctly.

Thank you this is really helpful.

 

[Slippery]

The Intex pump for a 3000 gal pool definitely won't work for roof panels. My 500 gph pump had a max head of about 7 feet. My 1000gph pump is probably bigger than yours and has maybe 10 feet at most. In any case it can't clear the air out of my 1.5 inch down pipe even at 5 feet. With these Intex pumps solar panels have to be ground level (below the water line) to work properly.

Regarding mounting on your north facing roof. ..don't bother...it won't work. Panels need to be south facing.

Do you have a bubble solar cover? Do you keep it on all times except for swimming? That makes a big difference.

When are you 4 hours of sun? If it's midday the extra sun hours may not be worth the effort. Especially in September when the sun is weaker and the warm sunny days fewer.

If you want to extend the season an actual heater works a lot better than solar panels around here. I suspect the same where you are.

pump: 1000gph
no solar cover: looking into one for next season
4 hour of sun are 11am-3pm
I am in the pacific north west when it's non stop sun all summer: fall and winter and nonstop clouds.

 

[Slippery]

The cheapest way is to use nails. You want to put a lot of weight on top of the structure that your house requires to keep you dry and the walls erect? As a former general contractor that's like asking what's the cheapest used tires I could by for my wife or daughter's car. Asking that question with the follow up indicates to me that you would be well served by doing some research on solar cell placement, pump requirements, solar cell sizing needs and a bunch of other things. The previous responses are well supported. If you don't understand loads, structure, placement and sizing, this project is waaay beyond a diy project based upon a few questions here.

You bring up some good points. Asking here is part of my research. I hadn't considered the extra weight that would be on the roof. My house is 99 years old and the more I learn about con

The previous posts have all mentioned the solar cover so as being crucial. I wasn't aware they made that big of a difference.

So I am going to try a different placement of the panels, bring them off the ground with a simple wood frame (I've read that the grass can act as a heat sink.) and get a solar cover and see if that brings the temps up more.

Thanks for your insight, It is very appreciated.

Here's a good question: what part of the sun in the pacific northwest is the strongest for water heating as the day goes on? this will help my panel placement

 

[mas985]

For heat gain from the sun, it is all about angle of incidence to the panels (normal incidence is better). If solar noon is at 1 pm, 12 pm or 2 pm is going to have exactly the same heat gain assuming the panels are pointed directly to solar noon.

However, the first component of heat loss is dependent on air temperature and air temperature tends to rise and peak after solar noon. So between morning and afternoon, there will be more net heat gain in the afternoon.

The second heat loss component is radiation heat loss, the largest component. If you can shield the panels to the general sky, but not the sun, you can reduce heat loss significantly. Trees work great for radiation heat shielding. You just don't want them shielding the sun.

The third component is conduction. As you pointed out elevating the panels above ground can reduce that.

 

[Slippery]

For heat gain from the sun, it is all about angle of incidence to the panels (normal incidence is better). If solar noon is at 1 pm, 12 pm or 2 pm is going to have exactly the same heat gain assuming the panels are pointed directly to solar noon.

However, the first component of heat loss is dependent on air temperature and air temperature tends to rise and peak after solar noon. So between morning and afternoon, there will be more net heat gain in the afternoon.

The second heat loss component is radiation heat loss, the largest component. If you can shield the panels to the general sky, but not the sun, you can reduce heat loss significantly. Trees work great for radiation heat shielding. You just don't want them shielding the sun.

The third component is conduction. As you pointed out elevating the panels above ground can reduce that.

Your response sent me off into a Google frenzy. I know so much more now. Let me make sure I understand.

When you say "normal incidence" You're saying to use the angles I got from this calculator for the correct time of year: Solar Angle Calculator Solar Panel Angle Calculator ? If were to angle the panels for September it would be 44 degrees Here in Portland, OR.


You say "shield the panels to the general sky, but not the sun, you can reduce heat loss significantly".I am confused by the use of the word "shield" here. In fact I am confused by this whole statement. Oh wait, are you saying I should build some kind of insulator for the panels? And by "general sky", you mean air?

Solar Noon: This calc ESRL Global Monitoring Division - Global Radiation Group says solar moon for me year round is between 12:10 and 12:15pm. So what you're saying is I should find out where solar noon for the time of year I most want heating and aim my panels at that for efficiency?

 

[Poolzzz]

Solar noon today was 1:10 pm local time in Portland, OR.

For radiation heat loss you're trying to shield from deep space actually. Use a radiation barrier.

 

[Dirk]

When I discussed placement for my pool's solar panels with the guys that sold them to me (solar installers), they convinced me that north facing was fine. That pool solar panels are way less sensitive to the kinds of angles you all are discussing than PV solar panels are. So I pointed mine north and saved my south-facing roof for my PV solar panels (and glad I did).

That's not to say that there must some be perfect direction to point pool solar panels, and if you have the option to do so, then why not. But I'm wondering how correct my mentors were, that with pool solar panels it's not all that critical. It's a series of black tubes heating in the sun. If they were pointing directly at the sun, instead of perpendicular to the sun's rays, then yes, that would produce less heat. But would 5 or 10 or even 45 degrees off of perpendicular make any measurable difference?

 

[mas985]

When you say "normal incidence" You're saying to use the angles I got from this calculator for the correct time of year: Solar Angle Calculator Solar Panel Angle Calculator ? If were to angle the panels for September it would be 44 degrees Here in Portland, OR.

Normal incidence is a 90 degree angle from the surface of the panels to the sun so the sun rays are orthogonal to the panel surface. When the angle of incidence is off normal, there is less projected capture area of the panels to the sun by the cosine of the angle off normal and there is less heat gain.

For example, if the elevation of the sun is 15 degrees off zenith (75 degree elevation) and the roof has a 15 degree pitch and the panels are pointed at solar noon, the panels are capturing all the sun they can at that point in time. However, on the north side of the roof, there will be 30 degree angle of incidence so the loss in heat gain is about 14% lower than the south side of the roof. So if you want heat gain to be the same, you need more panels. The steeper the roof, the more pronounced the effect. As the sun moves across the sky, the effect is even more pronounced. North facing panels work, just not as well.

You say "shield the panels to the general sky, but not the sun, you can reduce heat loss significantly".I am confused by the use of the word "shield" here. In fact I am confused by this whole statement. Oh wait, are you saying I should build some kind of insulator for the panels? And by "general sky", you mean air?

Heat is gained from the sun in the direction of the sun only. However, radiation losses occur in all directions and are proportional to the fourth power of the absolute temperature difference between the panel and sky. The sky temperature is typically 20-30 degrees below the air temperature so a lot of heat can be loss between the panels and the sky. If there is an object (buildings, trees, etc) between the panels and any portion of the sky, this heat loss is reduced because the objects tend to be at a higher temperature.

Also, wind breaks such as trees and fences can help because this reduces the wind across the panels.

Solar Noon: This calc ESRL Global Monitoring Division - Global Radiation Group says solar moon for me year round is between 12:10 and 12:15pm. So what you're saying is I should find out where solar noon for the time of year I most want heating and aim my panels at that for efficiency?

I think you forgot to check the DST box.


Also, I have a spreadsheet in my signature that will estimate all the heat gain and loss of a swimming pool with solar panels at a particular location so you can see the effects of different panel placing. It will also allow you to specify simple shadow masks for both the sun and the sky.

 

[Dirk]

Wow, thanks Mark. I got some of that, but enough to know I could have gotten more out of my panels. 14% (or whatever the loss is in my case) is not insignificant. I didn't have a choice though. I'm sure it's better that I pointed my PV solar south, and so only had a north facing roof available for my pool's panels...

I think I also understood that all I need to do to make up for the loss is to add another panel or two.

 

[Dirk]

Also, I have a spreadsheet in my signature that will estimate all the heat gain and loss of a swimming pool with solar panels at a particular location so you can see the effects of different panel placing. It will also allow you to specify simple shadow masks for both the sun and the sky.

Can you point me to that? I don't see which one you're referring to when I click around on your links.

 

[mas985]

Hydraulics 101 - Have you lost your head?

It is the heat transfer sheet:

https://drive.google.com/uc?export=download&id=0Bw8ON_7zALxWeFlLOUxiN0ZmMGs