420706-UUM-A-1008
HOW YOUR GAS FURNACE WORKS
Your furnace is a very easy appliance to take for granted. Season after
season, it sits there in your home, keeping you warm and comfortable.
For this reason, you may never have given much thought to the way
your furnace operates. In order to get the safest and most efficient oper-
ation from your furnace, you should understand how your furnace does
its job.
When you set your thermostat to provide more heat in your home, you
are starting the heating cycle of the furnace. First, the inducer motor
starts to purge the heat exchanger of any remaining gases. Next, the
hot surface ignitor glows and after a warm-up period the gas valve
opens and ignition occurs. A short time later, the blower starts and dis-
tributes the warm air throughout the home. When the temperature set-
ting on your thermostat is reached, the gas valve closes, the main
burners are turned off, and the blower continues to run until the remain-
ing warm air in the system is distributed. When the blower stops, the
heating cycle has ended.
1. This appliance does not have a pilot. It is equipped with an ignition
device which automatically lights the burner. Do not try to light the
burner by hand.
2. BEFORE OPERATING; smell all around the appliance area for
gas. Be sure to smell next to the floor because some gas is
heavier than air and will settle on the floor.
3. Use only your hand to push the gas control switch to the "on" posi-
tion. Never use tools. If the switch will not operate by hand, don't
try to repair it, call a qualified service technician. Force or
attempted repair may result in a fire or explosion.
4. Do not use this appliance if any part has been under water. Imme-
diately call a qualified service technician to inspect the appliance
and to replace any part of the control system and any gas control,
which has been under water.
OPERATING INSTRUCTIONS
1. STOP! Read the safety information above for your protection.
2. Set the thermostat to the lowest setting in the heat mode.
3. Turn off all electric power to the appliance.
4. Remove furnace burner access panel/door.
5. Move gas control switch to the "OFF" position. Do not force. See
Figure 3.
6. Wait five (5) minutes to clear out any gas. If you then smell gas,
STOP! Follow "B" in the safety information above. If you don't
smell gas, go to next step.
To Gas
Supply
To Gas
Supply
Ground
Union
Ground
Union
Gas
Valve
Gas
Pipe
Upflow
Configuration
FIGURE 4: Upflow/Downflow Gas Piping
7. Move gas control switch to the "ON" position. Do not force. See
Figure 3.
8. Replace furnace burner access panel/door.
9. Tum on all electric power to the appliance.
10. Set thermostat to the desired setting. Burner will light, which may
take 30-60 seconds.
11. After three (3) trials for ignition, if the appliance will not operate fol-
low the instructions, "TO TURN OFF THE APPLIANCE" and call
your service technician or gas supplier.
TO TURN OFF THE APPLIANCE
1. Set the thermostat to lowest setting in heating mode.
2. Tum off all electric power to the appliance if service is to be per-
formed.
3. Remove furnace burner access panel/door.
4. Move gas control switch to the "OFF" position. See Figure 3.
5. Replace furnace burner access panel/door.
LAWARNING!
Should overheating occur, or the gas valve fail to shut
off,
turn the external manual gas valve in the gas supply line to
the furnace to the "off" position and let the furnace cool
off
before shutting
off
the electrical power supply.
OUTLET
PRESSURE
PORT
INLET --.
VENT PORT
WRENCH
BOSS /
INLET/
PRESSURE
PORT
ON/OFF SWITCH
(Shown in ON position)
FIGURE 3: Single Stage Gas Valve
Ground
Union
Ground
Union
Gas
Valve
Gas
Pipe
Downflow
Configuration
Johnson Controls Unitary Products
3
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