Fv Sensor - A.O. Smith GPVL-50 Service Handbook

FLAMMABLE VAPOR SENSOR
When using a gas fi red water heater there is a risk of
fl ammable vapors entering the combustion chamber, being
ignited by the burner fl ame and causing a fl ashback. In
order to detect such fl ammable vapors before they enter
the combustion chamber, this water heater is equipped
with a fl ammable vapor sensor (FVS). It is a chemical-
absorption based sensor that is connected to the gas
control/thermostat (see Figure 31). When exposed to
fl ammable vapors it will trigger the control to stop the
fl ow of gas and enter the FVS lockout state. While in the
FVS lockout state the LED on the control will fl ash the
gas lockout code. Refer to the "Gas Control Led Status
Codes" section for an explanation of the codes applicable
to the control installed on your water heater. If an FVS
lockout occurs, check around the water heater for sources
of chemical contamination such as fl ammable vapors
including gas vapors, solvents, paint and thinners as well
as sources of water and detergents.
Note: Resetting the heater will reset the FVIR circuit if
all sources of contamination have been removed and the
sensor clears. If all sources of contamination have been
removed and the system will not reset, the sensor will
need to be replaced.
If there is a problem with the wiring of the fl ammable vapor
sensor or the fl ammable vapor interface the LED will fl ash
the failure status code (see "Troubleshooting Guide").
* ROTATE LEFT (CCW)
TO REMOVE
COVER*
Figure 31

FV SENSOR

MOUNTING
BRACKET
FLAMMABLE
VAPOR SENSOR
(PULL TO REMOVE)
27