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66386-YUM-C-1011
Johnson Controls Unitary Products 3
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 a manual reset high tem-
perature 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, preventing the flow of gas to the valve. 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. The
gas supply to the furnace should be shut off and no attempt
should be made to place the furnace in operation. The sys-
tem 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 after three ignition attempts, the flow of
gas 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” position.
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.
If the furnace continues to lock out, a qualified service techni-
cian should be called to determine the cause of the problem.
FIGURE 2- TYPICAL INSTALLATION
ELECTRICAL SHOCK, FIRE OR EXPLOSION HAZARD
Failure to follow safety warnings exactly could result
in dangerous operation, serious injury, death or prop-
erty damage.
Improper servicing could result in dangerous opera-
tion, serious injury, death or property damage.
• Before servicing, disconnect all electrical power
to furnace.
• When servicing controls, label all wires prior to
disconnecting. Reconnect wires correctly.
• Verify proper operation after servicing.
Prior to any of the following maintenance procedures,
shut off all power to the unit to avoid personal injury.
M a in G a s
S h u t - o f f V a lv e
F ie ld In s t a ll e d
( M o u n t e d E x t e r n a lly )