Main Components - Rinnai REU-V2632FFUG Service Manual

9. Main Components

1) Printed Circuit Board (PCB)
• The Printed Circuit Board controls all operational functions including Air Supply Control, Gas Control,
Water Flow Measurement, Water Flow Control, Combustion System and all sensors and safety devices.
2) Gas Flow Control
• During normal operation, the PCB keeps the main solenoid valve open whilst there is flow through the
unit and the burner needs to be lit.
• Gas flow rate is controlled by the modulating valve assembly and changeover solenoid valves to always
ensure constant outlet water temperature, regardless of flow rate or incoming water temperature.
• The modulating valve is electronically controlled by the PCB using signals from the water flow sensor,
water flow control device, by pass flow control device, water temperature thermistors and combustion
fan speed sensor. The modulating valve directs gas to the changeover solenoid valves.
• The changeover solenoid valves direct gas to each of the three burner banks independently. Any of the
solenoid valves may be open during operation.
• Gas flow is modulated by a combination of the modulating valve and changeover solenoid positions.
• The max imum gas rate is p redetermined and th e appliance ca nnot b e ov erloaded w hen correctly
installed.
3) Water Flow Control
• Water flow is detected by a turbine coupled to a magnetic pulse ge nerating device.The magnetic pulses
are detected and c ounted by the PCB.The PCB calculates the exact water fl ow from the frequency of
pulses generated by the turbine, as well as the volume of water that has passed through the unit at any
instant during 'Bath F ill' operation. A minimum flow rate of 2.4 l/min is requir ed for the burner to
ignite.
• Water flow control is achieved through the use of servo driven water flow and bypass valves. Both servo
motors are controlled by the PCB.The 'Water Flow Valve' restricts the flow of water into the heat
exchanger ass embly if the progra mmed tempera ture cannot be achieved. Also, when the Bath Fill
function is activated, flow of water is stopped when the bath is full. During normal operation, cold water
from the inlet valve is mixed with hot water from the heat exchanger outlet.The 'Bypass Valve' mixes
the correct proportion of c old and hot w ater to ensure accurate hot water delivery temperature over the
available range of flow ra tes. The water flow a nd bypass valves a re a c ombined assembly on the cold
water inlet of the appliance.
4) Air Supply Control
• Air for combustion is supplied by a centrifugal fan driven by a variable speed DC motor. The voltage to
the motor is determined by the PCB based on water flow, delivered water temperature and programmed
water temperature. The actual fan speed is monitored by a magnetic pulse counter. This counter emits a
signal to the PCB. F rom the volt age supplied t o th e DC motor and t he fan sp eed signal, the P CB
determines whether an error condition exists with the fan.
5) Combustion System
The combustion chamber is housed within the heat exchanger assembly and comprises:
• A multi chamber alumi nium alloy ma nifold with multiple injectors, arranged i n mult iple rows. The
middle chamber houses eight
injectors. Gas flow to ea ch cham ber is controlle d by an elec tronic solenoid valve (refer 'Gas Flow
Control' above).
• A burner assembly comprising multiple identical modular st ainless steel bunsen burners secured by an
aluminised steel fra mework. The ma nifold is atta ched to t he front of t he burner module. Each bunsen
burner is supplied by two injectors.
• A c ombustion chamber . Integra ted into the c ombustion chamber front panel are the flame rod a
ignition electrode(s).
Infinity REU-V2632FFUG / HD200i REU-VM2632FFUC
injectors, the left chamber, twelve, and the right
- 12 -
chamber, multiple
nd
Issue 1 - 16/12/09 ©Rinnai