·
A mixture of glycol and water is circulated from the
geyser to the solar collector and back using a small circulating pump.
·
The glycol/water mixture is heated in the solar collector
and pumped through the heat exchanger inside the geyser. Heat is transferred to the water inside the geyser and the glycol/water
mixture is pumped back to the solar collector to be heated again.
·
No water is heated directly with the solar collector,
but is heated indirectly with the heat exchanger.
· A differential controller controls the pump. The controller has sensors that monitor the
temperatures at the collector outlet and geyser’s outlet to the collector. When the temperature difference is 8oC
the controller switches the pump on and when the difference is 4oC the controller switches the pump off.
· The back up heating element can also be controlled via the controller maximizing on electricity
savings.
· The solar controller controls and protects the system against high water temperature and
wastage during periods of low hot water consumption and possible freezing of the water in the pipes to and from the collector.
·
The propylene glycol/water mixture inside the closed
loop is kept under 2 bar pressure by means of an expansion tank.
·
The mixture can be varied to suit the weather conditions
(minimal environmental temperature) in the area where the solar system is installed.
% glycol in water
Freezing Point
20%
- 7oC
30%
- 13oC
40%
- 23oC
50%
- 34oC
A mixture of 30% is generally used.
·
Propylene glycol is used to ensure that if a leak in
the system occurs, it would not be
harmful to people.
· The
client does not qualify for an Eskom rebate on an indirect system.
