Heating your SPA/Jacuzzi with the Sun

Spa heating is different than pool heating, although quite similar in that both make use of the existing filter pump for solar circulation. The usual spa water temperature is warmer than a pool and cooler than household hot water.

Usual Hot Water Temperatures	F^o	C^o
Pool	78	25.5
Spa	104	40
House Hot Water	130	54.5

The pool heaters work well and with a cover the pool water mass saves the heat. A spa is smaller and will not hold the heat for long, although a clear cover for an outside spa works quite well.

A spa can be connected to a solar collector and circulate water during the day to get it heated by the sun. If the spa is used in the evening, when there is no sun, then additional hot water is needed. Simply, the spa does not have enough mass to keep the heat. Extra stored solar heated spa water in a tank or a heater is needed to make the spa water the required temperature.

Four ways to heat a spa with solar:

1 - The pool owner uses a manual diverter valve that sends the spa water through the collector(s) when the spa filter pump is working and there is enough sun (needs a supplemental source of warm water to keep it toasty after the sun is down).

2 - Automatic controller works an electric diverter valve that does the same as above. There are temperature sensors to determine if the solar collector is warmer than the spa. If the spa is 3-5 degrees cooler than the collector panel, and not too hot, the diverter valve opens to let pumped water in the roof panels to circulate and absorb the solar heat

3- Automatic controller combined with a storage tank heats water in the spa and an insulated tank so there is sufficient hot water to be able to add some from the storage tank when needed.

4 - Automatic controller sends the spa water through a heat exchanger that is connected to a solar hot water storage tank. This same solar water storage tank can supply hot water for household needs as well since the water from the spa is not in direct contact with the solar heated water. This tank also serves as a backup heater if set up with a heat pump or other heating unit. Besides the spa filter pump, this system uses a small circulating pump to move the water from the storage tank through the heat exchanger the same time the spa pump moves the water through the other side of exchanger. DSCN3117

These copper panels are heating a large Jacuzzi in Guanacaste, Costa Rica at the Tierra Pacifica Environmental Estates

Escazú , Costa Rica

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