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035-18843-000-A-0402
Unitary Products Group 3
When the room thermostat is satisfied, the electrical
circuit to the gas valve is opened, closing off both main
burner and pilot gas simultaneously. If the pilot burner
should fail to light, contact your heating contractor or
gas utility for service to insure that proper operating
conditions are restored.
INPUT
The correct heat capacity of the furnace is regulated by
the burner orifices and the gas pressure. The proper
orifices are furnished but the gas pressure regulator
must be adjusted by the installer or gas utility service
technician.
OPERATING INSTRUCTIONS
TO SHUT DOWN THE FURNACE:
1. Close the main gas shutoff valve(s).
2. Turn off the electric power supply.
TO LIGHT THE FURNACE:
1. Do not attempt to light manually.
2. Open the main gas shutoff valve(s).
3. Adjust the set point of the room thermostat above
the temperature in the space.
4. Turn on the electric power supply.
5. The draft fan will operate. After an adequate purge
time, the electric spark igniter will light the burners.
6. The burners will extinguish and relight automatically
upon the demand of the room thermostat.
VENT SAFETY SYSTEM:
This gas furnace is equipped with an automatic reset
high temperature sensor or rollout switch which in the
unlikely event of a sustained main burner flame rollout
will shut off the flow of gas by closing the main gas
valve. The ignition modules will also be disabled, pre-
venting the flow of gas to the valves. The switch is
located inside the gas heat access panel above the
burner inlet. Flame rollout can be caused by blockage
of the power vent system, improper gas pressure or
adjustment. If this event occurs the furnace will not
operate properly, gas supply to the furnace should be
shut off and no attempt should be made to place the
furnace in operation. The system should be inspected
by a qualified service technician. Refer to Figure 2 for a
typical installation.
100% SHUT OFF:
The ignition modules are designed for 100% shut-off. If
the furnace fails to ignite within 85 seconds after a call
for heat, the flow of gas (including pilot) will be shut off
and the ignition module will lock out. The module can
be reset by:
A. Turning the system switch on the room thermostat
to the “OFF” position and back to the “HEAT” posi-
tion.
B. Decreasing the set point of the room thermostat
below the temperature in the conditioned space
and returning it to its original setting.
C. Opening and closing the unit's main disconnect
switch.
FIGURE 2: TYPICAL INSTALLATION