Lennox EL297DFV Series Unit Information page 35

3. Gas Valve
The valve (FIGURE 51) is internally redundant to assure
safety shut-off. If the gas valve must be replaced, the
same type valve must be used.
24VAC terminals and gas control knob are located on the
valve. A wire harness connects the terminals from the gas
valve to the electronic ignition control. 24V applied to the
terminals energizes the valve. Inlet and outlet pressure
taps are located on the valve. A regulator adjustment
screw is located on the valve.
LPG change over kits are available from Lennox. Kits in-
clude burner orifices and a gas valve.
4. Flame Rollout Switches (S47)
Flame rollout switch is a high temperature limit located on
top of the burner box, one on each side. See FIGURE 14.
The limit is a N.C. SPST manual-reset limit. When S47
senses rollout, the circuit breaks and the ignition con-
trol immediately stops ignition and closes the gas valve.
Rollout can be caused by a blocked heat exchanger, flue
or lack of combustion air. The switch is factory set to trip
(open) at 210°F and cannot be adjusted. The switch can
be manually reset. To manually reset a tripped switch,
push the reset button located on the control.
Intake Air Top Cap
Rollout Switch
Burner Box Cover
HEATING COMPONENTS
Sensor
Rollout Switch
FIGURE 14
5. Burners
All units use inshot burners. Burners are factory set and
require no adjustment. Always operate the unit with the
burner box front panel in place. Each burner uses an ori-
fice that is precisely matched to the burner input. Burners
can be removed as a one piece assembly for service. If
burner assembly has been removed, it is critical to align
center of each burner to the center of the clamshell when
re-installing. See more detail in Section VI- MAINTE-
NANCE.
6. Primary Limit Control (S10)
The primary limit (S10) is located in the heating vestibule
panel. When excess heat is sensed in the heat exchanger,
the limit will open. If the limit is open, the furnace control
energizes the supply air blower and closes the gas valve.
The limit automatically resets when unit temperature re-
turns to normal. The switch must reset within three min-
utes or the SureLight control will go into Watch guard for
one hour. The switch is factory set and cannot be adjust-
ed. The switch may have a different set point for each unit
model number. See Lennox Repair Parts Handbook if limit
switch must be replaced.
Manifold And Gas Orifices
Two-Stage Gas Valve
Page 35
Burner Assembly
Ignitor