CONNECTIONS – ELECTRICAL
45
BOOSTER CONTROL
The isolating switch installed in the electrical meter box for the solar storage tank should be left switched on.
Leaving the isolating switch switched on will also provide a sufficient period of time each day for the booster
heating unit to operate, if required, to satisfy the requirements of AS 3498.
Timer Control Switch
A suitably rated timer control switch can be installed and will help maximise energy savings with an
electrically boosted solar water heater connected to a
continuous, time of use
or extended Off-Peak
(overnight and day)
electricity supply.
If used with an extended Off-Peak (overnight and day) electricity supply, the timer switch should:
be operated by a continuous power supply on its own circuit from the switchboard with the booster
heating unit operated by the Off-Peak power supply. A double pole isolating switch is required to be
installed at the switchboard to simultaneously isolate both circuits.
or
be of a type which has an internal rechargeable battery to keep time when the power supply is not
available to the timer.
Programming the Timer
Power must be available to the timer control switch before the booster heating unit can be activated. The
timer control switch should be programmed:
to suit the hot water consumption pattern of the household,
with the end of the period to coincide with the commencement of the evening hot water usage,
to enable a boosting period of not less than the recommended continuous length of time for boosting,
for a period when power will be available to the timer.
It may be necessary to program a second period into the timer, such as prior to the morning hot water usage.
Check with the householder.
The recommended continuous length of time for boosting is:
Booster heating unit size
Model
Minimum winter
cold water temperature
Temperature
rise
2.4 kW
3.6 kW
4.8 kW
270
Cool / temperate climate
10°C
50°C
3 ½ hours
2 ½ hours
1 ¾ hours
Temperate / sub tropical climate
15°C
45°C
3 ¼ hours
2 ¼ hours
1 ¾ hours
Tropical climate
20°C
40°C
2 ¾ hours
2 hours
1 ½ hours
320
Cool / temperate climate
10°C
50°C
4 ¼ hours
3 hours
2 ¼ hours
Temperate / sub tropical climate
15°C
45°C
3 ¾ hours
2 ½ hours
2 hours
Tropical climate
20°C
40°C
3 ½ hours
2 ¼ hours
1 ¾ hours
410
Cool / temperate climate
10°C
50°C
5 ½ hours
3 ¾ hours
2 ¾ hours
Temperate / sub tropical climate
15°C
45°C
5 hours
3 ¼ hours
2 ½ hours
Tropical climate
20°C
40°C
4 ½ hours
3 hours
2 ¼ hours
The recommended boosting periods are sufficient to allow the booster heating unit to heat up the boost
volume of the solar storage tank to 60°C where the winter cold water temperatures do not fall below those
shown. This may be necessary during periods of no or very low solar energy gain through the solar
collectors, such as during constant rain or extremely cloudy weather, particularly in winter when the incoming
cold water temperature is lower. The period will also provide a sufficient heat up time for the electric booster
to operate, if required, to satisfy the requirements of AS 3498.
