Split System Solar Hot Water

Key Features

A Solar ‘split system’ has the solar collectors on the roof and a storage tank on the ground. The Collectors harvest the sun’s heat and transfer it to the water. The efficent absorber plate provides reliable heating low to high solar gain areas.

Solar energy is transferred directly to the water as it is moved through the collectors by an electric circulator and the heated water is stored in the specially designed, ground mounted tank. The electric boosted models are equipped with an in-tank element to ensure a supply of hot water during periods of poor or no solar gain.

  • Stylish slimline design
  • Minimum visual impact
  • Can cut water heating energy use by up to 65%
  • Choice of collectors to suit high to low solar gain areas

How Split System Solar Water Heaters Work

With open circuit split systems, the water is circulated from the tank at ground level through the solar collectors by an electric pump called a ‘circulator’. As the sun heats the water in the solar collectors, the increase in temperature activates the circulator. The circulator switches on whenever the water in the solar collectors is hotter than the water in the solar storage tank. The circulator moves the hotter water from the solar collectors through the solar hot pipe to the solar storage tank and the cooler water from the solar storage tank is circulated to the solar collectors via the solar cold pipe to be heated by the sun’s energy.

This process continues whilst solar energy is available and the water in the solar storage tank requires heating. The circulator will deactivate when the water temperature in the solar storage tank is around 70°C to 75°C.

A split solar water heater is designed to be installed as an electric boosted solar water heater with its booster heating unit connected to a power supply, however it may be installed with an in-series continuous flow or storage booster. If installed with an in-series booster, then the electric booster heating unit will not be connected to a power supply.

Solar Operation

The operation of the circulator is controlled by the combination of:

  • the hot sensor located at the outlet of the solar collectors. The hot sensor measures the water temperature at the outlet of the solar collectors.
  • the cold sensor located at the solar cold outlet at the base of the solar storage tank. The cold sensor measures the water temperature at the bottom of the solar storage tank.
  • the differential controller located in the solar control unit.

As the sun heats the water in the solar collectors, the increase in temperature activates the circulator. The circulator switches on whenever the water in the solar collectors is hotter than the water in the solar storage tank. The circulator moves the hotter water from the solar collectors through the solar hot pipe to the solar storage tank and the cooler water from the solar storage tank is circulated to the solar collectors via the solar cold pipe to be heated by the sun’s energy.

This process continues whilst solar energy is available and the water in the solar storage tank requires heating. The circulator will deactivate when the water temperature in the solar storage tank is around 70°C to 75°C.

During normal operation if the amount of solar energy available reduces, such as when the sky becomes very cloudy or the sun becomes lower in the sky in the late afternoon, and the water no longer gains usable heat from the solar collectors, the circulator will deactivate. The water heater will then enter standby mode.

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Over-temperature Operation

The purpose of the Over-temperature operation is to reduce the amount of overheating or ‘stagnation’ of water in the solar collectors. When the water in the solar storage tank has reached 70°C to 75°C and the circulator has deactivated, the solar collectors will continue to gain heat while solar energy is still available.

If the water in the solar collectors stagnates and its temperature becomes very high, the circulator will activate for a short period to transfer this extra energy to the solar storage tank. The circulator will deactivate when the water temperature in the solar collectors decreases. This process will either repeat for a maximum of eight cycles or until the water temperature in the solar storage tank reaches around 75°C to 80°C or the hot sensor does not sense another increase in water temperature to a stagnation level after a cycle is completed, i.e. the solar energy available reduces.

Night Time Cooling Operation

The purpose of Night Time Cooling operation is to rid the solar storage tank of excess solar energy gained by Over-temperature operation during that day. The desired water temperature in the solar storage tank is to be between 60°C to 70°C.

If the solar control unit has entered Over-temperature operation during the day, then after the water temperature in the solar collectors reduces later in the day or early evening, the circulator will activate. Water from the solar storage tank will circulate through the solar collectors and excess heat in the water will radiate from the solar collectors reducing the temperature of the water. The water will circulate for a period of time and until the water temperature in the solar storage tank is around 60°C to 70°C. The water heater will then enter standby mode.

Freeze Protection Operation

The purpose of Freeze Protection operation is to prevent freezing of water in the solar collectors and solar pipe work in very cold conditions. The water in the solar collectors will cool during periods of no solar gain. In very cold conditions, such as overnight and very early in the morning before sunrise, the water temperature can approach freezing point.

If the hot sensor measures that the water temperature in the solar collectors is approaching freezing, the circulator will activate. Water from the solar storage tank, containing more energy than the water in the solar collectors, will circulate through the solar collectors keeping the water temperature above freezing point. The circulator will remain on for some minutes and until the hot sensor measures a water temperature at a safe level above freezing. When both of these conditions are met, the circulator will deactivate. The water heater will then enter standby mode.

This process will repeat whenever the hot sensor measures that the water temperature in the solar collectors is approaching freezing.

Standby Mode

The water heater will be in Standby mode whenever conditions are not favourable for solar heating in Normal operation, and Over-temperature operation and Night Time Cooling are not required or have been completed, and conditions are not cold enough for or in-between Freeze Protection operation.

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    Product(s) / Service(s)

    Solar Hot WaterSolar PowerSolar Pool Heating