EcoSolar Energy Conscious Design Limited
9
In summary the solar water heating system must be promoted with the correct level of savings else, it
is unlikely that the customer will be satisfied with the system. The type of system is key to the
reliability of the system and the sizing and control of the system are key to the performance of the
system and energy savings achieved.
Caution
There are several issues that you should be aware of and manage prior to installing a solar hot water
system.
Building consent and Code Compliance
You will be required to submit a building consent for the installation of a solar hot water system. An
owner occupier can undertake some of the installation however, in order for the building consent
application to be signed off and a Code of Compliance Certificate granted, a registered plumber will
need to check, complete the installation including connecting in to the existing hot water system or
potable water reticulation and sign off the installation.
Heat Rejection
All solar hot water systems must have a method of discharging heat in event of a control or power
failure. Without a suitably sized method of rejecting heat, in the event of a thermostat or control
system failure or excessive heat being supplied by the solar collector, the hot water cylinder could
explode causing serious injury / death and or damage. There have been many such cases and the
results can and often have been, catastrophic. It is therefore imperative that adequate heat rejection
be maintained.
As a general rule, each 1m
2
of solar collector should have at least 1.5kW of heat rejection capacity, if
in any doubt please consult a suitably qualified and competent Engineer. These systems of relief must
not have isolation valves installed between the heat source and the relief discharge point. Also take
precautions to prevent the hot water discharge from causing damage to building elements or scalding
persons. These discharge points must not be long enough to allow freezing and therefore allowing
pipe blockages to occur. This requires a tundish or air gap to be present at the discharge point of the
relief valve and the relief valve piped away safely. The relief may be hot and therefore the relief drain
from a solar water heating system shall be of copper, not of plastic.
System Temperatures
Solar systems are able to heat the water to very high temperatures this leads to the following
concerns,
•
temperature of water delivered from taps.
A tempering valve must be installed to limit the
water temperature delivered at the taps. If there is already one installed, its correct operation should
