Turning up the solar set temperature does NOT heat your pool faster!

August 5, 2022

Here’s one I see ALL the time: pool owners set the solar set temp in the 90’s because they think that the higher they set the temperature, the faster the pool will heat. That is not the case.

The ‘Set Temp” is an end-point to stop heating your pool. The central heat & air system in your home works just like the solar panels on your roof: when you’re cold and you want to heat your home, you set the thermostat to let’s say…. 73 degrees. The heater turns on and it keeps heating your home until it reaches 73. If you set the thermostat to 90, the heater doesn’t produce more heat, it just keeps running until the sensor detects 90 degrees, then it turns off the heater off (these systems aren’t like our stoves where we can control how much heat is generated by adjusting the knob to control the flame size [or electric burner output]).

Solar on your roof is EXACTLY the same as your central heat system. When the pool water is 78 degrees and you want it to be 85, you set the solar controller to… 85. When the sensor on the roof detects that it’s hot enough on the roof to effectively heat water, the solar valve turns and water is sent to the roof. Water goes through all the little tubes in the solar panels and absorbs heat while passing through them. This continues to happen until your water temperature sensor (usually between the pump and filter) detects it’s 85 degrees. At that point the valve at the equipment pad closes to stop sending water to the roof. If you set the temperature to 96, the pool won’t heat any faster, water will just continue up to the roof and through the panels until the water reaches 96 degrees.

You may be asking, ‘Ok, Mike, I set the temp to 96, what’s so bad about that?’
Well, if you live where we live (in the Greater Sacramento area), it gets HOT here. Today it was 103. Do you know how hot it was on roofs? At least 130+. So, if you set your solar to 96 the pool water may get to 96! Do you want to swim in a pool that’s 96 degrees (please tell me nooooooooooo!) I know how hard it is to keep a pool clear and sanitized that’s 96 and I want no part of it!

Are there any options to get your pool to heat faster?
Yes. You could:

• add more solar panels to your roof. The more panels the more volume of water can pass through them which heats the pool faster
• put a solar blanket or solar rings/squares on your pool. They will magnify the water to help it heat a little faster but are most effective at keeping the heat in the water so it doesn’t escape at night when it cools off. For instance, if you heat your pool and it gets to 82,  when the weather cools at night, heat will escape from the pool water and it falls to 75. The next day you have to start heating from 75. If you have a blanket or solar rings/squares on your pool, it might cool to 72. Then the next day you’re 7 degrees ahead of pace
• use a gas heater to supplement heating the pool. If you don’t have a gas heater, see the Gas section of this article. If you do have a gas heater, most controllers allow you to use your solar to primarily heat the pool and then you can top it off with the gas heater

I hope this helps!
Sincerely,
Mike the Poolman
Folsom, CA