Solar Retrofit and Split Pump Water Heating Systems Operation

An Overview of the Operation of a Solar Geyser Retrofit or Split Pump System

The most energy intensive appliance in the home is the hot water cylinder or geyser. It is also the most expensive to run.


The good news is that solar water heaters can replace up to 100% of the electricity used to heat water (30% of the total electricity cost) in a normal household. Solar water heating should be considered as one of the first steps in energy and cost savings and providing a better return on investment than other renewable energy saving or generating technology in the South African environment.

Helderberg Solar Energy did many Solar Geyser Retrofit conversions and complete Split Pumps Systems – also called forced circulation systems.

A pump system is implemented when the solar hot water collector is higher than the geyser or hot water tank.

In a phermosiphon solar hot water system the collector is lower than the geyser and heated water rises towards the geyser and at the same time sucks colder water from the geyser.

If the solar hot water collector however is higher than the geyser this is not possible. Heated water by the sun will just stagnate in the collector and can reach dangerously high temperatures, even boiling point. In this case a circulation pump is used to circulate water between the geyser (hot water tank) and the collector.

Mostly Retrofit installations are Split Pump Systems where the solar water collector is either higher or at the same level as the geyser, in which case a Phermosiphon System is not possible.

Geyser – Solar Hot Water Collector Circulation

Helderberg Solar Energy make use of a 12V Circulation Pump, which is powered by a 10 Watt 12V Solar Panel, to circulate water between the geyser and the solar collector panel.


This option eliminates the need to have electricity for running the circulation pump.

An added benefit is that auto pump control is achieved without the need of an additional controller (and capital layout).

As soon as sunlight reaches the solar water collector and starting to heat up the water, sunlight also reaches the PV panel, which in turn generates DC power to power up the 12V solar pump and starts circulating water between the geyser and solar collector.

The opposite happens when there is no sunlight – no water is heated by the collector, the pump and circulation also stops.

Geyser Timer

To accomplish more savings at night time when no solar heating is possible or during cloudy days when it is less effective, we install a timer to be able to control when the geyser element (backup) kicks in to heat up the water. The timer can be set for different times every day and has a manually override.

3 Different modes are possible:

- Auto (Timed control)
- On (Override – permanent on)
- Off (i.e when away for Holiday)

The element is still controlled by its build-in thermostat, therefor if the water has been heated by the solar collector during the day and is still above the thermostat setpoint (normally 55°C), the element will not switch on.

This means the element backup will only kick in during the on times set with the geyser timer if the water temperature is below 55°C.

Solar Water Collector


We install either ITS or Sunscan Flat Panel Collectors for our Retrofit Systems. They are Ultra High Efficiency Collectors and carries a 5 to 10 year warranty.

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