Installation manual

14
TWIN FLOW MAINS COLD WATER PIPEWORK
The mains cold water pipework for the water heater of the Twin Flow should be sized
based on the maximum flow rate through it. If a high temperature set point is to be
used such as 55 or 60C then the maximum flow rate through the heater (based on a
summer incoming temperature of 20C, which is the maximum allowable in the UK) is
around 20 L/min. For lower setpoints the maximum flow rate through the heater
could be as high as 32 L/min. Based on a maximum water flow velocity of 1.5 m/s
the water supply to the heater should be 22mm regardless of set point. 15mm pipe
can be used but it will increase the pressure drop and flow velocity and may lead to
water hammer.
The water heater must have an isolating valve (supplied with the Twin Flow) and
union connection for removal of the appliance.
The flow switch supplied with the Twin Flow must be installed on the cold water inlet
to the heater. The wiring from the switch will be to the control box inside the back
plate. DO NOT USE HOT WORKS ANY WHERE NEAR THE FLOW SWITCH
UNDER NO CIRCUMSTANCES MUST THE FLOW SWITCH BE
REMOVED OR DISCONNECTED FROM THE BOILER CONTROL
CIRCUIT
The filling loop for the boiler (supplied with the Twin Flow) should branch off of the
mains cold water upstream of the water heater isolating valve.
If a secondary return is to be used the mains cold water pipe must have a full
unvented kit installed. These, along with further details, are available from Rinnai
UK. The secondary return should be piped into the cold inlet of the water heater.
Mains Cold Pipe
Water Heater Boiler
Location for
filling loop T
Flow
Switch