EcoSolar Energy Conscious Design Limited
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system and automatically switches the wetback pump on only when there is heat available in the
wetback.
Solar water heating as a preheater
In most cases a solar system installed in either a commercial or higher specification domestic system
will have to act as a preheater. A solar preheated system ensures that there is hot water on demand,
the temperature of the hot water drawn off at the taps is not dependent upon the amount of solar
gain available, in this type of system the customers see a seamless supply of hot water delivered to the
points of use.
The solar preheated water can be supplied to the following boosting systems,
1.
an instantaneous gas water heater as shown in Figure 5 below. If the water being heated by the
solar system is up to temperature, the bypass valve in the hot water supply diverts the water around
the instantaneous gas heater, if the water is not up to temperature the bypass valve directs the water
through the instantaneous heater to be heated.
Figure 5. Direct solar water heating system being used as a preheater to an instantaneous gas heater
2.
a backup heated cylinder as shown in Figure 6 below. The solar heated water is supplied
from the preheat cylinder to the boosting cylinder as its cold water supply. The boosting cylinder
may be heated by electric elements, gas boiler or another heat source. Figure 6 below shows an
EcoSolar drainback system operating as a solar preheating system with a boiler heated booster
cylinder.
