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Flammable Vapour Sensor
When using a gas fired water heater there is a risk of flam-
mable vapours entering the combustion chamber, being
ignited by the burner flame and causing a flashback. In
order to detect such flammable vapours before they enter
the combustion chamber, this water heater is equipped with
a flammable vapour sensor (FVS). It is a chemical-absorp-
tion based sensor that is connected to the gas control/ther-
mostat (see Figures 22 & 24). When exposed to flammable
vapours it will trigger the control to stop the flow of gas and
enter the FVS lockout state. While in the FVS lockout state
the LED on the control will flash the gas lockout code.
(Refer to the “System Error Codes” section of this manual
for an explanation of the codes applicable to the control
installed on your water heater.) If this error occurs, check
around the water heater for sources of chemical contamina-
tion such as: flammable vapours including gas vapours, sol-
vents, paint and thinners as well as sources of water and
detergents. Remove any such sources, check the sur-
– 18 –
Figure 21 Flammable Vapour Sensor (exploded view)
SCREW
MOUNTING
BRACKET
FLAMMABLE
VAPOUR SENSOR
(PULL TO REMOVE)
COVER*
* ROTATE LEFT (CCW)
TO REMOVE
AIR PRESSURE
SWITCH
BLOWER
GND
L1
N
IGNITER
FLAME
SENSOR
GAS VALVE
SOLENOID
POLARITY SENSITIVE DO NOT MIS-
MATCH WIRING. FAILURE TO CONNECT
CORRECTLY WILL PREVENT THE UNIT
FROM FUNCTIONING PROPERLY.
FLAMMABLE
VAPOUR
SENSOR
CONNECTOR
HIGH LIMIT
SWITCH
Figure 22 Gas Control/Thermostat Details and Wiring Diagram (Robertshaw)
GAS CONTROL
SWITCH (ON)
OUTLET TO MANIFOLD
DOOR ASS’Y (UNDER)
3/4” NPT. WRAP
WITH TEFLON TAPE
(2 WRAPS MIN.)
GAS VALVE
SOLENOID
CONNECTOR
FLAMMABLE VAPOUR
SENSOR 2 PIN
MOLEX CONNECTOR
QUICK CONNECTS
FOR POWER SUPPLY
AND IGNITER
TERMINAL BLOCK BLOWER
AND JUNCTION BLOCK 8
PIN MOLEX CONNECTOR
GAS CONTROL-VIEW OF ELECTRICAL
CONNECTORS, WITH COVER REMOVED
INLET
PRESSURE
PORT
OUTLET
PRESSURE
PORT
(UNDER)
GAS INLET
1/2” NPT
SYSTEM
STATUS
CODES
LED INDICATOR
140F MAX. DIAL
GROUND CONNECTION
160F MAX. DIAL
MANIFOLD
PRESSURE
ADJUSTMENT
(REMOVE
DIAL FOR
ACCESS)
GAS CONTROL-VIEW FROM GAS INLET
WITH TEMPERATURE DIAL REMOVED