York PC9 service manual YUM-A-0106, How Your Gas Furnace Works, Start-Upand Shutdown Instructions

172988-YUM-A-0106

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. The furnace control will vary the amount of heat and the amount of airflow needed to maintain the proper temperature in the home.

START-UP AND SHUTDOWN INSTRUCTIONS

Read the Instructions Below Before Trying to Start the Furnace

If you do not follow these instructions exactly, a fire or explosion may result causing property damage, personal injury, and/or loss of life.

A.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.

B.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.

C.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.

D.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.
2.	Set the thermostat to the lowest setting.
3.	Turn off all electric power to the appliance.
4.	Remove burner door.
5.	Move gas control switch to the “OFF” position. Do not force.
6.	Wait five (5) minutes to clear out any gas. If you then smell gas,

To Turn Off the Appliance:

1.Set the thermostat to lowest setting.

2.Turn off all electric power to the appliance if service is to be per- formed.

3.Remove burner access panel.

4.Move gas control switch to the “OFF” position.

5.Replace burner access panel.

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. Refer to Figure 5.

				MAIN
				REGULATOR
				ADJUSTMENT
INLET					OUTLET
PRESSURE					PRESSURE
TAP					TAP
	ON/OFF
	KNOB
FIGURE 4: Gas Valve - White Rodgers
		EXTERNAL MANUAL
		SHUTOFF VALVE
	TO GAS		TO GAS
	SUPPLY		SUPPLY

	GROUNDED JOINT UNION
DRIP	MAY BE INSTALLED
LEG	INSIDE OR OUTSIDE UNIT.

FIGURE 5: Gas Piping

MANUAL

SHUT-OFF

VALVE

STOP! Follow “B” in the safety information above. If you don’t

smell gas, go to next step.

7. Move gas control switch to the “ON” position. Do not force.

GAS PIPE

DRIP LEG

8.	Replace burner door.
9.	Turn on all electric power to the appliance.
10.	Set thermostat to the desired setting. Burner will light, which may
	take 30-60 seconds.

GAS PIPE

GAS BURNERS

GAS VALVE

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.

DRIP	MANUAL
LEG	SHUT-OFF VALVE

FIGURE 6: Horizontal Gas Piping

NOTE: The spring-loaded safety cut-off switch, mounted on the blower deck, behind the indoor fan access panel will automatically cut off the electrical power supply to the furnace when the blower panel is removed. As a safety precaution, all electrical power and the gas supply to the furnace should be turned off before servicing.

Unitary Products Group 3