Operation Principles - Rinnai REU-VR3237WG Service Manual

8. Operation Principles

Hot Water Operation
1. Ignition
• Activate controllers (if fitted) and open the hot water tap (for full details regarding operation of
controllers refer to the 'Customer Operating / Installation Manual' supplied with water heater).
• When water flows through the unit, the water flow sensor rotates and sends an electrical 'pulse'
signal to the Printed Circuit Board (PCB). This signal is proportional to the water flow rate.
• The PCB sends electrical current to the combustion fan motor causing it to turn. The fan motor sends
an electrical pulse signal to the PCB. If fan rotation is OK, the main solenoid and changeover
solenoid valves open as required, the spark generator activates and the spark electrode ignites the
burner.
2. Water Temperature and Flow
• The PCB will automatically control operation of the internal components to achieve the programmed
temperature. When a high temperature rise is required, the PCB may cause the Water Flow Servo to
close partially resulting in a lower flow rate to achieve the programmed temperature. This is a
necessary operational feature of the unit.
• When operating in 'Bath Fill' mode, the signal from the water flow sensor is also used by the PCB to
compute the volume of water that has been passed through the unit at any instant whilst the bath is
filling.
3. Shut Down
• When operating in 'Bath Fill' mode, the PCB causes the Water Flow Servo to close when the
programmed Bath Fill volume has passed through the unit. Alternatively, flow is stopped when the
user closes the hot water tap.
• When water flow stops, the water flow sensor stops rotating and the pulse signal to the PCB stops.
The PCB then causes the main solenoid and solenoid valves to close and the burner is extinguished.
The combustion fan will continue to operate for some time to purge the combustion chamber.
Infinity REU-VR3237WG / HD250e REU-VRM3237WC - 11 - Issue 1 - 19/05/09 ©Rinnai