Lennox EL296UHE Series Unit Information page 18

C- Heating Components
1. Ignitor
The SureLight ignitor is made of durable silicon nitride.
®
The integrated control provides 120 volts to the ignitor
for a consistent ignition and long ignitor life. Ohm value
should be 39 to 70. See figure 14 for ignitor location and
figure 15 for ignitor check out.
NOTE - The EL296UHE furnace contains electronic com-
ponents that are polarity sensitive. Make sure that the fur-
nace is wired correctly and is properly grounded.
2. Flame Sensor
A flame sensor is located on the left side of the burner
support. See figure 14. The sensor tip protrudes into the
flame envelope of the left-most burner. The sensor can be
removed for service without removing any part of the burn-
ers. During operation, flame is sensed by current passed
through the flame and sensing electrode. The SureLight
control allows the gas valve to remain open as long as
flame signal is sensed. To check flame sense signal use
the push-button found on the integrated control and go to
Field Test Mode. The menu will display the flame signal.
See table 9 for flame signal.
TABLE 9
Flame Signal in Microamps
Normal
2.6 or greater 2.5 or less
3. Gas Valve
The valve (figure 14) is internally redundant to assure safe-
ty 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 include
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 control
immediately stops ignition and closes the gas valve. Roll-
out can be caused by a blocked heat exchanger, flue or
lack of combustion air. The wwswitch 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.
Low Drop Out
.06
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 adjusted.
The switch may have a different set point for each unit
model number. See Lennox Repair Parts Handbook if lim-
it switch must be replaced. When removing switch make
note of orientation. When replacing switch make sure the
three mounting holes are lined up with the screw holes in
the vestibule for correct orientation.
Primary Limit Control (S10)
Mounting Hole
Page 18
Mounting Hole
Mounting Hole
FIGURE 13