Rheem W2W Series Owner's Manual And Installation Instructions page 39

CONNECTIONS - PLUMBING
RELIEF VALVE
The heat pump is supplied with an integral pressure relief valve located on the
inside of the heat pump cabinet and will discharge into the tray of the heat pump.
Refer to Condensate Drain on page 39 for drainage instructions.
EXPANSION CONTROL VALVE
Local regulations may make it mandatory to install an expansion control
valve (ECV) in the cold water line to the water heater system. In other areas, an
ECV is not required unless the saturation index is greater than +0.4 (refer to
"Water Supplies" on page 14). However, an ECV may be needed in a corrosive
water area where there are sufficient quantities of silica dissolved in the water.
The expansion control valve must always be installed after the non return valve
and be the last valve installed prior to the water heater system (refer to diagram
on page 35).
EXPANSION CONTROL VALVE DRAIN
A copper drain line must be fitted to the relief valve to carry the discharge clear
of the water heater. Connect the drain line to the relief valve using a
disconnection union. The pipe work from the relief valve to the drain should be
as short as possible and fall all the way from the water heater with no restrictions.
It should have no more than three right angle bends in it. Use DN15 pipe.
The outlet of the drain line must be in such a position that flow out of the pipe
can be easily seen (refer to AS/NZS 3500.4) - but arranged so hot water
discharge will not cause injury, damage or nuisance. The drain line must
discharge at an outlet or air break not more than 9 metres from the relief valve.
In locations where water pipes are prone to freezing, the drain line must be
insulated and not exceed 300 mm in length. In this instance, the drain line is to
discharge into a tundish through an air gap of between 75 mm and 150 mm.
CONDENSATE DRAIN
A drain line may be fitted to the condensate drains to carry the discharge clear
of the water heater. The drain line can be extended using 20 mm O.D. rigid hose
or conduit. Where installed externally, the drain line pipe work must be UV
resistant or protected from sunlight. The outlet of the drain line must be in such
a position that flow out of the pipe can be easily seen - but arranged so water
discharge will not cause damage or nuisance.
The condensate drain must not be connected to the pressure relief or
expansion control valve drain line but may discharge at the same point.
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