Download Solar System Components, Configurations and Operating Principles

3 Solar system components, configurations and operating principles
Image: Courtesy of Solahart.
Figure 3.4.2 – Over-heating dissipater
Supplementary heater or booster types
A booster element can be either electric or gas. Electric boosters are usually located
in the middle of the tank so that they heat the water above. Elements fitted to tanks
for the colder regions have a curved or ‘sickle’ element fitted with the sickle pointing
down to boost heat more water when connected to off-peak electricity tariffs. A
thermostat switches the element off when the water reaches the desired
temperature, typically about 60ºC. They are generally rated at 2.4 or 3.6 kilowatts of
power.
Gas boosters can either be tank mounted to heat the tank water directly or a
separate in-line instantaneous gas booster after the storage tank. Gas boosters are
generally rated at between 13 (tank mounted) and 200 Megajoules per hour (in-line
instantaneous type), providing fast recovery time. Electronic ignition systems are
used to avoid wasting gas with a pilot light. Electricity is required to operate the
electronic control, which turns on the gas when the water temperature drops and a
spark ignites the gas. A big advantage of the electronic ignition is the ability to control
it from a remote location and disable the burner during daylight hours. Figure 3.4.3
shows details of a close coupled system with integral tank gas boosting and a heat
dump pipe at the rear of the storage tank. The inlet and outlet valves are also shown.
This system provides 97% of the hot water to the Brisbane home of the author and
his wife.
Details of booster operation and control are given in Chapter 4 (Boost Heating).
Solar Water Heater Training Course – Installer and User Manual
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