INSTALLATION – SOLAR STORAGE TANK
30
If a combination isolation valve and non return valve (duo or trio valve) is
installed on the cold water line to the solar water heater and the cold water line
to the temperature limiting device branches off after this valve, then a second
non return valve must be installed between the cold water branch and the solar
storage tank. Due to the higher water temperatures generated under certain
conditions in the solar collectors of this solar water heater, an effective back-
flow prevention device should be used as the second non return valve as an
extra safeguard. Valve manufacturer RMC recommends Dual Check Valve
model N7150, as being suitable for this application.
If a pressure limiting valve is installed on the cold water line to the solar water
heater and the cold water line to a temperature limiting device branches off
before this valve or from another cold water line in the premises, then a
pressure limiting valve of an equal pressure setting may be required prior to the
temperature limiting device.
CIRCULATED HOT WATER FLOW AND RETURN SYSTEM
A solar water heater should not be installed as part of a circulated hot water
flow and return system in a building. The benefits of solar gain will be
significantly reduced and energy gained from the sun lost through the pipe
work.
If a circulated flow and return system is required, it is necessary to bypass the
solar water heater and install a secondary water heater connected to the hot
water flow and return line and supplied from the solar water heater. The
secondary water heater must be a storage water heater able to provide a hot
water outlet temperature of at least 60
°
C.
Note:
The thermostat must always
be set to at least 60
°
C. Refer to the
diagram on page
31.
Temperature Limiting Device
A temperature limiting device cannot be installed in circulated hot water flow
and return pipe work. The tempered water from a temperature limiting device
cannot be circulated. Where a circulated hot water flow and return system is
required in a building, a temperature limiting device can only be installed on a
dead leg, branching off the circulated hot water flow and return pipe.
If circulated tempered water were to be returned back to the water heater,
depending on the location of the return line connection on the water supply line
to the water heater, then either:
