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Installation Types

Thermosyphon - On Roof System

A Thermosyphon system relies on the physics of nature to circulate the water [direct system] or glycol [indirect system]. As hot air rises so does hot water because hot water is lighter than cold water. No mechanical or electrical process is required to transfer the heat. The heat generated in the solar collector is transferred directly to the water in the tank [direct system] or through heat exchanger [indirect system].

The tank and the collector are installed on the roof. A thermosyphon system is highly efficient and requires less maintenance than a pumped system.


Thermosyphon - Split System

A thermosyphon split system works on the same physics of nature as a thermosiphon on the roof system. Whereas the collector is installed on the roof but the tank is installed inside the roof. This installation requires the tank to be installed at least 300mm above the collector. The pitch of the roof needs to be steep and a height of two meters is required inside the roof for the thermosyphon to work efficiently.


Pumped Split System

A pumped split system has the collector installed on the roof but the tank is installed anywhere below the collectors. Therefore the thermosyphon can’t work.

One needs a pump and a controller to regulate when the pump needs to pump.

There are two options with the kind of pump to choose. One can either install an AC or DC pump. An AC pump consumes electricity but tends to be more efficient and its lifespan for some reason or another is longer than a DC pump. The advantage of a DC pump it consumes no electricity. It has its own solar panel. When the sun is up it will pump as regulated by the controller.


What is Q-Factor?

Solar water heaters generate heat through the solar collector with the heat transferred through the solar collector and stored in the water vessel or tank. This solar thermal process is substituting the electricity used in heating water through an electrical resistance element. The performance of a solar water heater is tested by the South African National Standards. SANS 6211 measures the energy collected and stored during a day, using 6 representative sample days of different solar irradiation. This represents a sample performance of the typical weather in South Africa over a period of a year.

SANS 6211 results in a 'Q' test result. Dividing the 'Q' by 3.6 results in the deemed saving equivalent in kWh's as calculated at 20MJ irradiation, which is the average across South Africa. A maximum performance is stipulated as 10MJ per 50 litres of water per day under SANS 1307, and a minimum performance of 5MJ per 50 litres.

The minimum and maximum Q factors allowed are:


100 litres

150 litres

200 litres

250 litres

300 litres

Min Output - “Q”






Max Output - “Q”






The minimum and maximum electrical savings output in kWh is, therefore:


100 litres

150 litres

200 litres

250 litres

300 litres

Min Output - ‘kWh’s’






Max Output - ‘kWh’s” 






The ‘Q’ factor is, therefore, an extremely important indicator of the performance of the solar water heating system chosen. Much in the same way as kilometres per litre of diesel or petrol vehicle, it provides a measure of performance, but it is not the only criteria for choosing an SWH system. With the purpose of a Solar Water Heater being to heat hot water and save electricity, the efficiency of the solar water heater is an important factor in choosing the SWH system. In reality, no SWH system can be 100% efficient due to weather, but some systems come close.

To calculate the efficiency of a system take the Q test figure at 20MJ and divide by the Q factor for 100% theoretical efficiency. For example Size of System in (litres). Electrical Consumption from Cold to Hot (kWh). Q factor required for 100% Efficiency. Q Factor on SWH system (illustrative) Efficiency Rating in %

Litres             Elec.Cons     Q-Factor 100%   Q-Factor SHW    Efficiency Rating

150L              7,67                  27,62                     23                         83%

200L              10,23               36,83                      32                         87%

250L              12,79               46,04                      38                         83%

300L              15,34               55,25                      46                         83%




People often ask me, “Do I really need to service my solar geyser?” A service on a solar geyser is mainly preventative maintenance, if done on a regular basis. I am going to list what we do and show some photographs of systems that were not serviced regularly.

  • The tank needs to be flushed to remove a build-up of water sediment and sludge.     The condition of the tank is looked for decay, inside and outside.
  • An Indirect system can need the glycol refilled because there is loss from evaporation.
  • A direct system needs the water to be flushed to cleanse the collector from any sediment build up. From the picture below one can see the dirty water being released.


  • The thermostat setting is checked that it is set at a maximum of sixty degrees, in our opinion it lengthens the life span of thermostat if not set on the maximum. If the thermostat is malfunctioning or damaged, it is replaced. The picture below, one can see there was an electrical short that damaged the thermostat that had to be replaced.


  • The Element connection is checked, that it is power at the element and working properly. It will be replaced if damaged or not working.
  • The Flange gasket is replaced if damaged. From this picture one can see the flange gasket was torn and this will cause water leaks.


  • Excessive dust build up on the collector is removed.
  • Lagging is checked for perishing from the UV rays of the sun that damages the lagging. The damaged lagging will be replaced.
  • The timer is checked to see if it working properly. The settings are checked. To ensure the minimum water temperature is not too high. Ideally the timer should run between two hours and a maximum of four hours per day.


  • The solar geyser is checked for any damage or potential problems. From the photograph below, one can see water was leaking onto the electrical element, that we noticed during a service.


  • Brackets are checked to ensure the tank is secure, that there are no screws that are badly rusted or broken.
  • The anode by design are sacrificial to prevent the element from being damaged from the chemicals in the water. The anodes are checked for wear & tear and replaced if required.


  • Electrical wires are checked for any lose connections or if any terminals are badly rusted that could cause a problem. The below controller box that had an electrical short and burnt out the PC board in the first picture. The second photograph is an example of rusted terminals that cause a communication error to the controller.


  • There is natural wear & tear on the valves, this is checked to see if there is any malfunctioning of a valve. Valves & shut off valves are checked for any leaks and tighten if required. Broken & damaged valves are replaced if necessary.



Why does one service a solar geyser?

  • Solar geysers have working parts and if it is not serviced yearly, the geyser could possibly stop working, a valve leaks or gets stuck open.
  • Preventative maintenance always costs less than emergency call outs and repairs.
  •  Don’t you want to prevent the inconvenience caused from a solar geyser that is not working due to a failure that could have been prevented?
  •  Preventative maintenance allows you to have the full financial benefit from your solar geyser all year round.

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