Safety Lockouts; High Limit Controls (Energy Cut Off); Thermostat/Water Temperature; Blower High Limit Switch - A.O. Smith GPVX 75L Series Installation And Operating Manual

This water heater has several lockout features designed
to prevent the heater from operating in unsafe conditions.

HIGH LIMIT CONTROLS (ENERGY CUT OFF)

Thermostat/Water Temperature

This feature is a part of the gas control valve/thermostat
(see Figure 1, item 11) and limits the maximum water
temperature. In the event of the water overheating, this
safety feature shuts off the fuel supply to the burner. This
ECO is not resettable and the gas control valve/thermostat
will need to be replaced by a qualified service technician.

Blower High Limit Switch

This device is located on the blower (see Figure 6, item
49) and limits the maximum temperature of the blower.
If the blower temperature rises above the temperature
setting, the switch opens causing the heater to shut down.
The switch will auto reset once the temperature drops
sufficiently.

BLOWER AIR PRESSURE SWITCH

This device, located in the junction box, monitors the air
pressure produced by the blower. In the event that the
exhaust venting becomes blocked or sufficiently restricted,
the switch will shut the heater down (see Figure 6, item
47). If the water heater has not gone into a soft lockout
condition, the heater will restart after the blockage is
removed (see "Resetting The Heater Control").

FLAMMABLE VAPOUR SENSOR

When using a gas fired water heater there is a risk of
flammable 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-absorption based sensor that is connected to
the gas control/thermostat (see Figure 14). 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 Status And
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 contamination such as:
flammable vapours including gas vapours , 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 (see "Resetting The Heater Control").
12

SAFETY LOCKOUTS

If there is a problem with the wiring of the flammable
vapour sensor or the flammable vapour interface, the LED
will flash the failure status code (see "System Status And
Error Codes").
* ROTATE LEFT (CCW)
TO REMOVE
COVER*
FLAMMABLE
VAPOUR SENSOR
(PULL TO REMOVE)
Figure 14
MOUNTING
BRACKET
100271597