Rheem MPi 551 Series Owner's Manual And Installation Instructions page 22

INSTALLATION
CIRCULATED HOT WATER FLOW AND RETURN SYSTEM
An MPi 551 series heat pump water heater should not be installed as part of a circulated hot water flow and
return system in a building.
If a circulated flow and return system is required, it is necessary to bypass the heat pump water heater and
install a secondary water heater connected to the hot water flow and return line and supplied from the heat
pump 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 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 water heater, depending on the location of the
return line connection on the water supply line to the water heater, then either:
water will be supplied to the cold water inlet of the temperature limiting device at a temperature
exceeding the maximum recommended water supply temperature, or
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.
These conditions 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 either condition, the operation and performance of the
device cannot be guaranteed.
Circulated Hot Water Flow and Return System - Heat Pump Water Heater
REDUCING HEAT LOSSES
The cold water line to and the hot water line from the water heater must be insulated in accordance with the
requirements of AS/NZS 3500.4. The insulation must be weatherproof and UV resistant if exposed.
LEGEND
22