
TM090 12-26 Series II CFGWH Service Instructions
REV AB
– Issued February 2019
This document is stored and maintained electronically by Rheem Technical Support. All printed copies
are deemed “uncontrolled”
10
Voltages up to 240 volts will be present within the water heater, take care
not to touch wiring terminals. Use an insulated tool when adjusting
settings.
1. Switch DIP SWITCH 3 to the on (up) position on the PCB.
2. Push the MAX button to increase outlet temperature set point. Continue to press MAX
button until correct temperature is achieved at first tap used for personal hygiene
purposes. The maximum outlet temperature setting is 54ºC.
3. Once correct temperature set point is selected, switch DIP SWITCH 3 to the off (down)
position on the PCB.
SEQUENCE OF OPERATION
Refer to ‘Sequence of Operation Component Diagram’ on page 11 to view components
shown in brackets e.g.
(1)
1. When a hot water tap
(1)
is opened, cold water (or preheated water if a solar preheater
is installed) enters the water heater and passes through the Water Flow Sensor
(3)
and
Heat Exchanger
(19)
. Note: the inlet water temperature must be less than or equal to
58ºC and less than or equal to the set point temperature minus 2ºC for operation to occur
past this point; otherwise water will pass straight through the heat exchanger and fan and
burner operation will not occur (for more information on this subject refer to the section
titled ‘In-series Gas Boosting’ on page 12).
2. The Water Flow Sensor
(3)
sends a pulse signal to the PCB
(27)
. Once the pulse signal
reaches a pre designated frequency (at minimum flow rate) the PCB
(27)
activates the
Fan Motor
(25)
and the Fan
(24)
starts rotating.
3. After the Fan
(24)
completes a pre purge, the Gas Inlet Solenoid Valve
(9)
is activated.
Then Step 1 -
Gas Solenoid Valve 2
(11)
is activated, the Proportional Gas Flow
Regulating Valve
(13)
adjusts the gas flow rate through Steps 2
– 6, to ensure adequate
gas for ignition and gas is then supplied to the Burner
(15)
. (See page 11 Stepping gas
rate change sequence).
4. At the same time the Gas Solenoid Valves open the Igniter
(16)
starts sparking
continuously and ignites the gas at the Burner
(15)
. After the flame sensor
(18)
detects
burner flame, the Proportional Gas Valve
(13)
begins to control the gas flow rate. If there
is a difference between the hot water temperature detected by the Hot Water Outlet
Thermistor
(6)
and that set on the water heater or selected on the remote controller (if
fitted) the PCB
(27)
adjusts the hot water temperature by opening and closing the Gas
Solenoid Valves 1
(10)
, 2
(11)
and 3
(12)
and adjusting the Proportional Gas Flow
Regulating Valve
(13)
. The water flow rate is also adjusted via the Water Flow Servo
Motor
(7)
to ensure the selected temperature of hot water is delivered.
5. As the gas flow rate, controlled by the Proportional Gas Flow Regulating Valve
(13)
changes the PCB
(27)
varies the speed of the Fan Motor
(25)
to maintain the correct air
gas mix ratio.
6. When the hot tap
(1)
is closed, the pulse signal from the Water Flow Sensor
(3)
stops
and the burner flame is extinguished by closing Gas Solenoid Valves 1
(10)
, 2
(11)
, 3
(12)
and the Gas Inlet Solenoid Valve
(9)
. The post purge operation then commences.
7. Once the post-purge operation ends (up to 6 minutes) power to the Fan Motor
(25)
is cut
and the Fan
(24)
stops.