Report from American Microsolar ( :

Hello Siang, This is Larry writing.  Thought you may like to see the installation we did on the condominium complex spa here on Hilton Head.  It is working great and everyone is pleased.  The condo complex spent over $24,000. on propane last year so this is going to be a huge savings.  One that many pool and spa owners could use we feel.

In the photo you can see the gas heater to the left, our black heat exchanger at the bottom and the green electric pump.  There are two digital control boxes on the wall.  The one on the left shows the temperature of the water returning from the spa and shuts off the system if the water temp gets over 104F.  The box on the right is the temperature of the water in the units.  We have it set to start circulating when it reaches 136F and shut off when it gets down to 130F.  The gas heater only comes on when the temp drops to 99F.  The units get down to about 125F overnight and get up to 136F late in the morning and start working.  As long as the temp of the units water is 134-136F the water going into the gas heater after the heat exchanger is kept at 101F and the water returning from the spa is 100F.  When the units get down to 131-133F it still keeps the water after the heat exchanger at 100F so the gas heater doesn't come on except occasionally for only a short time.  The gas heater will come on every 12-15 minutes for 5 minutes without the solar running so it shows a huge savings.  This is only March and we know as the days get longer and the sun higher in the sky we will have even better performance.  As I said, everyone is pleased.

>>click here for pdf file