DIY Solar heating

[Klept]

Hi All. First I would like to comment on the great site and community here. I discovered TFP two days ago and haven't stopped reading and learning. Almost to a fault. Not a productive weekend on my part and I may have confused myself more than absorbing the right info.

We would like to install a hydronic solar heating system on the roof of the building (right one) in the pic. I am confused in which type of install may be most cost effect for install and operating. Coiled tubes in boxes, S shaped patterns on the roof, commercial panels etc.

Our pool surface area is 400 sq ft with a volume of 14K gallons. The cabana roof is a total 250 sq ft, flat. It is sloped ever so slightly for rain water run off. It is 12' floor to roof. Piping would not be a cost on its own as I have access to 1/2" up to 1". The pool pump is a 3hp pentair.

My initial thought of install was to tap in a supply and return to the pipe going into heater. I was thinking of installing a circulation pump on the return (vertically on the wall). I wasn't planning on installing a diverter valve for the solar loop, thinking the circulation pump will draw the water needed.?.

Before I ramble too long and risk jumping all over the place and risk providing irrelevant info, I will leave it at this point. If there is any info still needed please let me know.

 

[mas985]

Welcome to the forum!

Solar pool heaters and hot water solar heaters are too different designs. One is used to heat a lot of water just a little bit while the other is used to heat a little water a lot. Using a hot water design for a pool will results in less than satisfactory results. What you want is a lot of surface area with many very small tubes all in parallel for high flow rates and high efficiency. Something like a commercial pool solar panel:



Diyers generally use landscape tubing in coils much like this:

But if you go this route, it is best to use several coils in parallel to keep the tube length short and flow rates higher. One of the biggest mistakes DIYers make is to use one very long tube coiled up. That creates a lot of head loss limiting the amount of flow through the panel. Higher flow rates through the tubing results in better efficiency. This is what you want (although the pump is shown backwards and solar valves should be used):



For a 400 sq-ft pool, you will want at least 200 sq-ft of panels. Using 1/2" tubing (0.7" O.D.), that is about 3500' of tubing.

 

[Klept]

Thank you @mas985

Not sure if you're familiar with the panels attached, but if so, what is your opinion on them? They may be costly upfront but worth it over 5 years.?. I definitely will not be able to get 3500' feet of tubing on the roof.

Are there panels that you would recommend? The usable roof dimension is 25' x 10'.
You mention solar valves should be used. Can a circulation pump be used to draw the water through the panels? Much like an in floor hydronic system drawing from the primary loop. I only ask because I have two domestic water recirc pumps sitting in my shop I can put to use, if pool chemicals will not destroy brass pumps.

 

[mas985]

Have you priced those panels? I can't imagine them being very cost effective. With your size pool, you will want as many panels that will fit on that roof size.

Also, the pool pump is sufficient to run solar so no additional pumps are required if standard pool panels are used.

https://www.amazon.ca/6-2X12-SunQuest-Swimming-Heater-Complete/dp/B007NIPW8M/ref=sr_1_3?crid=1W1PRGKMLYFLG&keywords=Pool%2Bhot%2Bwater%2BSolar%2Bpanels&qid=1649174753&rnid=5264023011&s=lawn-garden&sprefix=pool%2Bhot%2Bwater%2Bsolar%2Bpanels%2Caps%2C154&sr=1-3&th=1

That is about $12/sq-ft

Other popular brands are Fafco, Techno-Solis, Helicol

The issue you are going to have with anything right now is going to be supply and cost. Everything is elevated.

 

[Klept]

I think the panels in the link you provided might be perfect for our scenario. I can get 9 (maybe 10) on the roof.

Is my idea for connecting ok? Assume the pipe I tie the supply / return to is from the heater to the SWCG (right under neath the pool return pipe). Blk square represents a two way valve in the off position.

Thanks again for all your advise. I hope to return the favour some day

 

[mas985]

Usually solar is tied in right after the filter and before the heater. This is done to maintain efficiency when both solar and heater are used at the same time.

 

[Telemachus]

I tied in right after the heater. Works great.

The heater acts as a pressure reducer and limits barotrauma on the panels, increasing their longevity.

I can't imagine a scenario where I'd use the gas and solar heater at the same time. Plus the Pentair Easytouch 8 doesn't even allow it.