Safety Lockouts; High Limit Controls; Thermostat/Water Temperature; Blower Exhaust Gas Limit Switch - John Wood POWER VENTED GAS FIRED WATER HEATER Installation And Operating Instructions Manual

SAFETY LOCKOUTS

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

High Limit Controls

Thermostat/Water Temperature

This feature is a part of the gas control valve/thermostat (see
Figure 35) and limits the maximum water temperature. In the
event of the water overheating, this safety feature shuts off the
fuel supply to the burner. If the high limit is tripped, it requires
manual resetting (see "ECO Reset").

Blower Exhaust Gas Limit Switch

This device is located on the blower (see Item 5, Figure 9) 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 suffi ciently.

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 suffi cently restricted, the switch
will shut the heater down (see Item 22, Figure 9).

Flammable Vapour Sensor

When using a gas fired water heater there is a risk of
fl ammable vapours entering the combustion chamber, being
ignited by the burner fl ame and causing a fl ashback. In order
to detect such fl ammable vapours before they enter the
combustion chamber, this water heater is equipped with a
fl ammable vapour sensor (FVS). It is a chemical-absorption
based sensor that is connected to the gas control/thermostat
(see Figure 33). When exposed to fl ammable vapours 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 "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 contamination such as: fl ammable
vapours including gas vapours, solvents, paint and thinners
as well as sources of water and detergents. Remove any such
sources, check the surrounding area for damage and call a
qualifi ed service technician to service the water heater and
replace the fl ammable vapour sensor. If there is a problem with
the wiring of the fl ammable vapour sensor or the fl ammable
vapour interface the LED will fl ash the failure status code (see
Table 2 - "System Error Codes").
* ROTATE LEFT (CCW)
TO REMOVE
Figure 33

Resettable Lockout

The gas control/thermostat can be reset by unplugging the
power cord to remove power and then reinserting the plug
to restore the power. Honeywell controls will automatically
attempt to reset after a 20 minute wait period.

Water Heater Operation

Figure 34 shows the water heater's sequence of operation
when a call for heat is initiated. The ignition control module will
attempt to light the burner three times. If the ignition control
does not detect ignition it will enter lockout mode and fl ash
the corresponding error code.
CALL FOR
HEAT
CONTROL CHECKS TO
ENSURE PRESSURE
SWITCH IS OPEN
BLOWER IS
ENERGIZED
CONTROL CHECKS TO
ENSURE PRESSURE
SWITCH CLOSES
INDICATING BLOWER
IS OPERATING AND
THERE ARE NO
VENTING BLOCKAGES
(INLET OR OUTLET)
Figure 34
– 21 –
COVER*
FLAMMABLE
VAPOUR SENSOR
(PULL TO REMOVE)
IGNITER IS
ENERGIZED AND MAIN
VALVE IS OPENED
MAIN BURNER ON AND
THE FLAME IS SENSED
BY CONTROL
MAIN BURNER
CONTINUES TILL THE
WATER IN THE TANK
REACHES
THERMOSTAT
SETTING
MAIN BURNER SHUTS
OFF. BLOWER
CONTINUES FOR A
POST PURGE TIME
MOUNTING
BRACKET