Here’s the 2020 update on the system:
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I added 2 more 2’x20’ solar collectors for a total of 320 sq/ft. That’s about 80 square feet more than the pool surface area. Why? We’re close to Lake Superior so our yard can be 10 degrees C cooler than 10 miles inland. Also the pool is shaded so does not get a lot of direct sun.
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All equipment is now plumbed into a small shed.
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I use the Intex pump (SF80110-1) in series with an inexpensive 2 speed pump (on low speed) which pumps 2 stories up and gets us about 1500 GPH at the pool outlet on solar heat. The combination uses about 5.4 amps.
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My little solar/rechargeable battery hack worked 100% all the way through winter so I did not replace any expensive lithium cells on the wireless temperature sensors. This “hack” uses three AA rechargeable cells connected to a cheap amazon solar panel (5.0V). The three fibaro door sensors (each with a DS18B20 digital temp sensor wired in) have the lithium cells removed and are directly wired to the AA battery back. These sensors change temps often, so will churn through the expensive lithium cells in 1-2 months. The sensors have not required any power, even idling through the winter at -35C low temps!. The sensors reported low battery at 1% all winter, but stayed running, and continue to run off their solar/cell system. Smarthings is definitely not showing the correct “charge” as the sensor array has been live now for about 18 months on 3 AA rechargeables
BTU output of the system will peak now at about 115 000 BTU with the 8 collectors.
June 17th, we saw an 8.6 F degree rise in the pool water (7000 gallons) to about 74 F. This means the system generated 501 466 BTU over the day…not bad considering the max air temp at the pool was 77 F at around 3:30pm.
This is a snapshot of the data on June 18th, at 2:43pm, a day or two after filling the pool. City water here is cold, about 49F coming out the the tap to fill the pool.
You can see air temps at the pool are not great, but the system is pumping out heat. Overall for the months of June, July and August, the pool temps averaged about 82 F, with a high of 86 F. For our climate and a shaded 7000 gallon pool, it looks like 8 collectors ( 320 square feet) is a good match. Temps last night dipped to 48 F (August 18) so heat loss at night is significant, however we’re still just at 82 F as I type this.