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-

* ROTATE LEFT (CCW)	SCREW
TO REMOVE	SCREW
COVER*

MOUNTING

BRACKET

FLAMMABLE

VAPOUR SENSOR (PULL TO REMOVE)

Figure 21 Flammable Vapour Sensor (exploded view)

GAS CONTROL

SWITCH (ON)

3/4” NPT. WRAP

WITH TEFLON TAPE

(2 WRAPS MIN.)

INLET

PRESSURE

PORT

GAS VALVE

SOLENOID

CONNECTOR

FLAMMABLE VAPOUR

SENSOR 2 PIN

160F MAX. DIAL

MANIFOLD PRESSURE ADJUSTMENT (REMOVE DIAL FOR ACCESS)

MOLEX CONNECTOR

QUICK CONNECTS

FOR POWER SUPPLY AND IGNITER

TERMINAL BLOCK BLOWER

AND JUNCTION BLOCK 8

PIN MOLEX CONNECTOR

	GAS INLET	OUTLET
	GAS INLET	PRESSURE
	1/2” NPT	PORT
		(UNDER)
	SYSTEM
140F MAX. DIAL	STATUS	LED INDICATOR
140F MAX. DIAL	CODES
	CODES

OUTLET TO MANIFOLD DOOR ASS’Y (UNDER)

GROUND CONNECTION

GAS CONTROL-VIEW OF ELECTRICAL

CONNECTORS, WITH COVER REMOVED

AIR PRESSURE

SWITCH

HIGH LIMIT	GND	L1	N

SWITCH

Figure 22 Gas Control/Thermostat Details and Wiring Diagram (Robertshaw)

GAS CONTROL-VIEW FROM GAS INLET

WITH TEMPERATURE DIAL REMOVED

FLAMMABLE

VAPOUR

SENSOR

IGNITER

BLOWER

FLAME

SENSOR

CONNECTOR

GAS VALVE

SOLENOID

POLARITY SENSITIVE DO NOT MIS- MATCH WIRING. FAILURE TO CONNECT CORRECTLY WILL PREVENT THE UNIT FROM FUNCTIONING PROPERLY.

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