INSTALLATION – SOLAR STORAGE TANK
29
CIRCULATED HOT WATER FLOW AND RETURN SYSTEM
The solar storage tank of 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.
If a circulated flow and return system is required, it is necessary to connect the circulation return line to the in-
series booster and not to the solar storage tank.
A Rheem 874826 model in-series gas booster can be installed as part of a circulated hot water flow and return
system in a building. The connecting pipe work supplied with the water heater may need to be modified in
order to install a Tee prior to the water inlet of the in-series gas booster. The circulated return line is to be
connected to the Tee.
Refer to the diagram
Circulated Hot Water Flow and Return System
on page 30.
If the in-series booster is a continuous flow water heater, then the circulator must be:
sized and set to provide a minimum flow rate of 3.0 L/min through the circulated hot water flow and return
system, and
either thermostatically and / or timer controlled.
The circulator
must not
be set to operate continuously, i.e. 24 hours per day.
Temperature Settings
AS 3498 requires that a water heater provides the means to inhibit the growth of Legionella bacteria in
potable water.
If the in-series water heater is a continuous flow water heater, to meet this requirement of AS 3498, its
preset outlet temperature setting must be set to 70°C or higher.
A Rheem 874826 model can satisfy this AS 3498 requirement provided it is energised and the booster
preset outlet temperature setting is 70°C or higher.
If the in-series water heater is a storage water heater, to meet this requirement of AS 3498, its thermostat
must always be set to at least 60°C.
Water should not be circulated from a water heater with a temperature setting of less than 60°C.
The return water temperature to the water heater must not be less than 55°C.
If the water temperature decreases by more than 5°C due to heat loss from the ring main, the preset outlet
temperature setting or thermostat setting of the in-series water heater must be set to above 60°C to ensure
the return water temperature is not less than 55°C.
Temperature Limiting Device
A temperature limiting device cannot be installed in circulated hot water flow and return pipe work. The
tempered water supplied from the tempered hot water outlet on this water heater or from another 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 or a dead leg
installed from the tempered water outlet of this water heater.
If circulated tempered water were to be returned back to the gas booster water heater, then when the hot taps
are closed no water will be supplied to the cold water inlet of the temperature limiting device whilst hot water
will continue to be supplied to the hot water inlet of the temperature limiting device.
This condition may result in either water at a temperature exceeding the requirements of AS/NZS 3500.4 being
delivered to the hot water outlets in the ablution areas, or the device closing completely and not delivering
water at all, or the device failing. Under this condition, the operation and performance of the device cannot be
guaranteed.
