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EL180UHE HEATING COMPONENTS
FIGURE 6
Gaskets
Collector Box
Orifice Plate
Flue Transition
Pressure Switch
Combustion Air Inducer
Manifold And Gas Valve
Ignitor
Rollout Switches
(-090, -110 -135 units)
Sensor
Rollout Switches
(-045 and -070 units)
5. Flame Rollout Switches (Figure 6)
Flame rollout switch (S47) is a high temperature limit. Each
furnace is equipped with two identical switches. The limit is
a N.C. SPST manual‐reset limit connected in series with
the integrated control A92. When S47 senses rollout, the
integrated control immediately stops ignition and closes
the gas valve. If unit is running and flame rollout is detected,
the gas valve will close and integrated control will be dis
abled. Rollout can be caused by a blocked heat exchanger,
blocked flue or lack of combustion air. The switch has a fac
tory setpoint of 210°F and cannot be adjusted. To manual
ly reset a tripped switch, push the reset button located on
the control.
6. Primary Limit Control
The primary limit on EL180UHE(X) units is located in the
heating vestibule panel under the combustion air inducer.
See figure 7. When excess heat is sensed in the heat ex
changer, the limit will open. If the limit is open, the inte
grated control energizes the supply air blower and closes
the gas valve. The limit automatically resets when unit tem
perature returns to normal. The switch must reset within
three minutes or SureLight
®
control will go into Watch
guard for one hour. The switch is factory set and cannot be
adjusted. The switch may have a different setpoint for each
unit model number. If limit switch must be replaced, refer to
Lennox ProductZone repair parts list on Lennox Dave
Net®.
FIGURE 7
Primary Limit Under Combustion Air Inducer
Primary
Limit
7. Flame Sensor (Figure 6)
A flame sensor is located on the left side of the burner sup
port. The sensor is mounted on the flame rollout plate and
the tip protrudes into the flame envelope of the left-most
burner. The sensor can be removed for service (clean with
steel wool) without removing any part of the burners. Dur
ing operation, flame is sensed by current passed through
the flame and sensing electrode. The integrated control al
lows the gas valve to remain open as long as flame signal is
sensed.
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