Swimming Pool Solar Heaters Solar Pool And Spa Heating Basics

Pool and spa heating is one of the most popular and cost-effective uses of solar heating and solar hot water systems. By incorporating a number of solar collectors and a specialized solar heat exchanger, known as a shell & tube heat exchanger, with your existing pool or spa circulation system, you can provide free and efficient heat for your pool or spa.

Traditional pool and spa heating systems typically run on electric, natural gas or electric heating fuels. The problem is that these traditional fuels are more expensive than ever before, and their prices continue to rise day after day.

However, a solar pool or spa heating system can easily cut 50%, or more, off of your pool and spa heating costs – saving hundreds, even thousands, of dollars a year in energy costs. What could you do with a few extra hundred dollars, or more?

Solar Pool & Spa Heating System Components:

A solar pool & spa heating system has several key components, that when combined together create an efficient and cost-effective heating system for you pool and spa. These components include:

  • Solar Collectors – whether you are using evacuated tube solar collectors or flat plate solar collectors, the solar collectors are the most integral part of your solar pool heating system.
  • Shell & Tube Heat Exchanger – a shell & tube solar heat exchanger is made from stainless steel. The chlorine in pool or spa water can easily damage copper heat exchangers, copper pipes and the copper headers in your solar collectors. By separating the chlorinated water in your pool from the HTF in the solar collector loop with a shell & tube solar heat exchanger, you can safely heat your pool water without fear of damaging your system.
  • Solar Circulator Pump – a circulator pump is critical for circulating the HTF through your solar collector loop. As HTF is heated in the solar collectors, the pump moves it to the shell & tube solar heat exchanger, where it transfers its heat to the pool/spa water, and then back to the solar collectors to be heated again.

  • Solar Controller – a specialized controller is a critical component of your solar pool or spa heating system. Your controller will need to read the temperature of your solar collectors and your pool or spa. Additionally, the controller will need to control the circulator pump in your solar collector loop, and the actuator/3-way valve that directs your HTF to the shell & tube solar heat exchanger when heating is needed/available.

  • 3-Way Valve & Actuator – a 3-way valve should be placed between the solar collectors and the shell & tube solar heat exchanger. The 3-way valve will divert your HTF to the heat exchanger when it can (and needs to) heat the pool or spa water, and directly back to the solar collectors when not. The actuator automatically operates the 3-way valve for simple, hassle-free operation. The actuator and 3-way valve controlled and operated by the solar controller.

Sizing A Solar Pool & Spa Heater:

For most residential backyard pools, sizing a solar pool heater is relatively simple and quick. There is a simple formula that most professionals use, and solar associations across the United States recommend.

The simple solar pool heater sizing formula is:

Area of Pool (ft2) * Sizing Factor = Area of Solar Collectors (ft2)

Sizing Factors:

  • Southern States: 50% (0.50)
  • Middle States: 75% (0.75)
  • Northern States: 100% (1.00)

Once you have determined the area of solar collectors that you need, you can simply determine the number of solar collectors you need by dividing the area of solar collectors needed by the “apterture area” of the solar collectors you would like to use.

SunMaxx Solar Collector Aperture Areas (popular pool heating collectors):

  • SunMaxx-30 Evacuated Tube Solar Collector: 30.04 ft2
  • SunMaxx-25 Evaucated Tube Solar Collector: 25.03 ft2
  • SunMaxx-FP Flat Plate Solar Collector: 19.68 ft2

Here is a quick example of solar pool heating sizing:

Pool size: 10′ x 20′ / Location: Florida

200 ft2 (area of pool) * 0.50 (sizing factor) = 100 ft2 (collector area)

100 ft2 / solar collector aperture area =

  • SunMaxx-30: 3 – 4 solar collectors
  • SunMaxx-25: 4 solar collectors
  • SunMaxx-FP: 5 – 6 solar collectors

Generally, you should round the number of solar collectors up, not down, to avoid an undersized benefit that does not provide enough heating capacity to be worth the investment.

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