Goodman [A/G]PG, Service Instructions Manual

Page: 20 / 52

20
SYSTEM OPERATION
The pressure tap has a predetermined orifice size for reading
static pressures. The induced draft blower motor assembly is
mounted to the collector box. When the motor is in operation,
a negative pressure will be created on the pressure tap, collec-
tor box and heat exchanger flue passages.
A pressure control using a single pole, single throw electrical
switch is used as a safety device in case of a blocked flue.
CONNECTOR
COMMON
TERMINAL
NORMALLY OPEN
TERMINAL
NEGATIVE PRESSURE
With the unit in the off position the induced draft blower motor
will not be running. Atmospheric pressure will therefore be on
both sides of the diaphragm and the electrical switch will be
open between (C) common and (NO) normally open terminals.
When the induced draft blower motor is in operation, it creates
a negative pressure on one side of the diaphragm and atmo-
spheric pressure on the other side causing the diaphragm to
move toward the negative pressure.
This in turn will close the switch and make the (C) common to
the (NO) normally open terminals.
In the event of partially restricted or blocked flue the induced
draft blower will create less negative pressure and will open the
contacts (C) to (NO).
OPERATING INSTRUCTIONS
1. Close the manual gas valve external to the unit.
2. Turn off the electrical power supply to the unit.
3. Set the room thermostat to its lowest possible setting.
4. Remove the heat exchanger door on the side of the unit by
removing screws.
5. This unit is equipped with an ignition device which auto-
matically lights the burners. DO NOT light burners by any
other method.
6. Turn the gas control valve to the OFF position. Do not force.
Some Gas valves may have a different off/on style switch.
Gas Valve
On/Off
Selector
Switch
INLET OUTLET
7. Wait five minutes to clear out any gas.
8. Smell for gas, including near the ground. This is important
because some types of gas are heavier than air. If you have
waited five minutes and you do smell gas, immediately
follow the lighting instructions of this manual (page 7). If
having waited for five minutes and no gas is smell is noted,
turn the gas control valve to the ON position.
9. Replace the heat exchanger door on the side of the unit.
10. Open the manual gas valve external to the unit.
11. Turn on the electrical power supply to the unit.
12. Set the thermostat to desired setting.
NOTE: There is approximately a 20-second delay between
thermostat energizing and burner firing.
FAN OPERATION
Continuous Fan Mode
If the thermostat calls for continuous fan without a call for heat
or cool, the indoor blower will be energized at the heat speed.
The fan remains energized as long as there is not a call for
heat or cool. Once the call for continuous fan is de-energized,
the indoor blower will go through a 60 second off delay.
If a call for cool occurs during continuous fan operation, the
blower will switch to the cooling speed.
If a call for heat occurs during continuous fan operation, the
indoor blower will de-energize when the heat on blower delay
begins. The heat cycle will control the indoor blower operation
until the heat blower off delay is over. The continuous fan
mode will function normally even while the control is in heat
lockout.