Rheem W2W Series Owner's Manual And Installation Instructions page 57

Note: The water heater may not turn on immediately when it is first switched on,
if it is switched on within 20 minutes to 2 hours of it having been switched off at
the isolating switch, or the heat pump has just completed a heating cycle. The
water heater will wait until the conditions for start-up are favourable in order to
protect the compressor from damage. This may take up to 20 minutes to 2 hours.
The auxiliary booster (if installed) will operate instead of the heat pump if the
temperature or the flow rate of the cold side is below the set point.
Explain to a responsible officer the functions and operation of the heat pump
water heater. Upon completion of the installation and commissioning of the water
heating system, leave this guide with the responsible officer.
Commissioning Procedure – Multiple Heat Pump (Master/Slave)
Configuration
Perform this procedure if the system is comprised of multiple heat pumps to be
configured for Master/Slave operation.

Open all of the hot water taps in the building (don't forget the showers) and
supply cocks and valves in the system.

Open the isolation valves fully on the cold, return and hot water branches to
the storage tanks.

Open the main cold water isolation valve on the cold water line to the storage
tanks.

Air will be forced out of the taps.

Close each tap as water flows freely from it.

Check the pipe work for leaks.
Before commencing the Master/Slave commissioning procedure, ensure the
'Multiple Heat Pump Installation
- step 1 and step 2 have been completed as stated on page 45.
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