Thought I would update how all this has been working out, with thanks for all the good guidance I was given here.
In a word, great.
We have a 20x40 35K gallon pool, and wanted to extend the season on both ends without going broke. I was given some personalized info, and read a million threads on TFP about propane (quick heat, no fuss, no weather requirements, $$$$$$$$$$), solar (weather-dependent, but almost free to operate) and heat pump (also weather dependent, with variable efficiency and electricity costs). I even looked at a wood-fired system, but it was too much like work.
We ended up with an Aquacal 140K heat pump, and 768 sq ft of solar panels. Pool is 800 sq ft, so panel area is a bit under 100%. I built an oversized pool house to accommodate the panels. They are mounted facing east and west, which is not ideal. And we’re in the woods so there is some tree blockage. The panels get a lot of sun in the spring and summer, not much in the fall.
I started heating on April 28, with pool water at 48 deg, and air temps in the 50's during the day and 30's at night. I'd turn on the east-facing solar loop in the morning, both sides during the day, and the west-facing in the afternoon. I would turn the heat pump on when air temps hit 50, which seems like the minimum for it to produce meaningful heat. I used an IR sensor on the pipes to see when the solar and/or HP were making heat. Pool stayed covered.
On May 3 the pool hit 72 deg, and the grandkids and I were in! Water was 80 on May 6, and heating was no problem going forward.
June through August steady state was mid to high 80’s. SunTouch controller worked well and activated the solar when heat was called for. HP was used once or twice during rainy spells. I occasionally pumped through the solar panels at night to get some cooling.
In September the solar contribution phased out, but the heat pump obligingly took up the slack. As of today (Oct 11), I’m running the HP whenever air is over 50, including overnight when possible. It is a battle now, pool can lose heat quickly, and the overnighters are needed. Pool temp has ranged from 77-89 in October. This weekend is supposed to be warm, and I’ll probably quit heating after that.
Swimming in October foliage with air temp at 55 and the pool at 89 is an experience!
Some lessons learned:
1. Solar and heat pump are a great tag team.
2. Solar likes sun, does well in the spring, and doesn’t mind colder temps during initial spring warm-up. Ambient temp needs to be within 20 degrees or so of pool temp, so with pool at 50 and air at 35, it will be heating.
3. HP doesn’t need sun, is happy in overcast/rainy conditions, and does well in the fall.
4. In Sept/Oct, everything is conspiring against solar: fewer hours of sun, the sun at a much lower angle, here the sun is usually behind trees, and the panels face east/west rather than south. So the solar contribution fizzled. Panels on a south-facing pitched roof, without trees, would perform somewhat better.
5. Delta T is also a factor in the fall. Solar needs air temp to be within 20 or so degrees of pool temp, so with pool at 85 and air at 55, no heat from solar. HP doesn’t care about pool temp and will add heat if air is >50.
6. It’s hard to measure heat output with any accuracy. I used an IR sensor on the pipes to get a rough idea.
7. Initial cost: HP purchase price was $5K plus wiring and plumbing. Solar was $6.5K plus controller, wiring and plumbing. I did the installation so didn’t pay for that. Solar panel install took me and a buddy (both of us with building/plumbing experience) a day.
8. Electricity cost: HP around $1/hour, solar maybe $1/day (pumping at higher speed).
9. Projected life cycle cost: considering initial purchase, electricity, and maintenance expenses, my annual cost over life expectancy for solar plus HP is $1800/year. This is not much more than HP alone which would have been $1600/year. Solar alone would have been $600/year.
10. Anything involving propane would have been much more expensive (natural gas not available here).
11. During late spring and summer I used a SunTouch solar controller since HP was rarely needed, which worked great once I got Pentair to help program it. Pretty much auto-pilot. However in spring and fall I controlled things manually, so hands-on involvement needed.
12. Must do freeze protection on cold nights.
13. Aquacal has given very good support answering questions, and sent out a tech under warrantee to take care of an issue.
14. Solar system came from Sun Source Energy Products in New Jersey, and I can’t say enough about their excellent support. They helped with all manner of configuration and installation info.
In a nutshell (or TLDR as the cool kids would say), solar/HP combo is pricey upfront but reasonable over life expectancy, and extended the season as much as we would want on both ends. Solar did the heavy lifting in spring, and HP took over in fall. Some hands-on tinkering needed.
In a word, great.
We have a 20x40 35K gallon pool, and wanted to extend the season on both ends without going broke. I was given some personalized info, and read a million threads on TFP about propane (quick heat, no fuss, no weather requirements, $$$$$$$$$$), solar (weather-dependent, but almost free to operate) and heat pump (also weather dependent, with variable efficiency and electricity costs). I even looked at a wood-fired system, but it was too much like work.
We ended up with an Aquacal 140K heat pump, and 768 sq ft of solar panels. Pool is 800 sq ft, so panel area is a bit under 100%. I built an oversized pool house to accommodate the panels. They are mounted facing east and west, which is not ideal. And we’re in the woods so there is some tree blockage. The panels get a lot of sun in the spring and summer, not much in the fall.
I started heating on April 28, with pool water at 48 deg, and air temps in the 50's during the day and 30's at night. I'd turn on the east-facing solar loop in the morning, both sides during the day, and the west-facing in the afternoon. I would turn the heat pump on when air temps hit 50, which seems like the minimum for it to produce meaningful heat. I used an IR sensor on the pipes to see when the solar and/or HP were making heat. Pool stayed covered.
On May 3 the pool hit 72 deg, and the grandkids and I were in! Water was 80 on May 6, and heating was no problem going forward.
June through August steady state was mid to high 80’s. SunTouch controller worked well and activated the solar when heat was called for. HP was used once or twice during rainy spells. I occasionally pumped through the solar panels at night to get some cooling.
In September the solar contribution phased out, but the heat pump obligingly took up the slack. As of today (Oct 11), I’m running the HP whenever air is over 50, including overnight when possible. It is a battle now, pool can lose heat quickly, and the overnighters are needed. Pool temp has ranged from 77-89 in October. This weekend is supposed to be warm, and I’ll probably quit heating after that.
Swimming in October foliage with air temp at 55 and the pool at 89 is an experience!
Some lessons learned:
1. Solar and heat pump are a great tag team.
2. Solar likes sun, does well in the spring, and doesn’t mind colder temps during initial spring warm-up. Ambient temp needs to be within 20 degrees or so of pool temp, so with pool at 50 and air at 35, it will be heating.
3. HP doesn’t need sun, is happy in overcast/rainy conditions, and does well in the fall.
4. In Sept/Oct, everything is conspiring against solar: fewer hours of sun, the sun at a much lower angle, here the sun is usually behind trees, and the panels face east/west rather than south. So the solar contribution fizzled. Panels on a south-facing pitched roof, without trees, would perform somewhat better.
5. Delta T is also a factor in the fall. Solar needs air temp to be within 20 or so degrees of pool temp, so with pool at 85 and air at 55, no heat from solar. HP doesn’t care about pool temp and will add heat if air is >50.
6. It’s hard to measure heat output with any accuracy. I used an IR sensor on the pipes to get a rough idea.
7. Initial cost: HP purchase price was $5K plus wiring and plumbing. Solar was $6.5K plus controller, wiring and plumbing. I did the installation so didn’t pay for that. Solar panel install took me and a buddy (both of us with building/plumbing experience) a day.
8. Electricity cost: HP around $1/hour, solar maybe $1/day (pumping at higher speed).
9. Projected life cycle cost: considering initial purchase, electricity, and maintenance expenses, my annual cost over life expectancy for solar plus HP is $1800/year. This is not much more than HP alone which would have been $1600/year. Solar alone would have been $600/year.
10. Anything involving propane would have been much more expensive (natural gas not available here).
11. During late spring and summer I used a SunTouch solar controller since HP was rarely needed, which worked great once I got Pentair to help program it. Pretty much auto-pilot. However in spring and fall I controlled things manually, so hands-on involvement needed.
12. Must do freeze protection on cold nights.
13. Aquacal has given very good support answering questions, and sent out a tech under warrantee to take care of an issue.
14. Solar system came from Sun Source Energy Products in New Jersey, and I can’t say enough about their excellent support. They helped with all manner of configuration and installation info.
In a nutshell (or TLDR as the cool kids would say), solar/HP combo is pricey upfront but reasonable over life expectancy, and extended the season as much as we would want on both ends. Solar did the heavy lifting in spring, and HP took over in fall. Some hands-on tinkering needed.
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