INSTALLATION – SOLAR STORAGE TANK
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, not the solar storage tank. A Rheem 874 series continuous flow water heater can be installed
as part of a circulated hot water flow and return system in a building.
Water must not be circulated from an in-series booster water heater with a thermostat or temperature
setting of less than 60°C. This setting should be increased if the water temperature decreases by more
than 5°C through a circulated hot water flow and return system due to heat loss in the ring main.
AS 3498 requires that a water heater provides the means to inhibit the growth of Legionella bacteria in
potable water. To meet this requirement of AS 3498:
an in-series continuous flow water heater must always have its preset outlet temperature setting set to at
A Rheem 874 series continuous flow water heater can satisfy this AS 3498 requirement provided it is
energised and the booster preset outlet temperature setting is 70°C or higher.
an in-series storage water heater must always have its thermostat set to at least 60°C
If the in-series water heater is a continuous flow water heater, 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.
Refer to the diagram Circulated Hot Water Flow and Return System – Solar Water Heater on page 22.
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 in-series 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
Circulated Hot Water Flow and Return System – Solar Water Heater