Goodman [A/G]PG, Service Instructions Manual

Page: 46 / 52

SERVICING
46
VOLT / OHM
METER
RED
RESET
BUTTON
COLOR
IDENTIFYING
TAB
TESTING AUXILIARY LIMIT CONTROL
S-302 CHECKING FLAME ROLLOUT SWITCH
APG/GPG units are equipped with a temperature-activated
manual reset control. This control is mounted to the manifold
assembly and is wired in series with the auxiliary limit and gas
valve. The control is designed to open should a flame roll out
occur. An over firing condition or flame impingement on the
heat shield can also cause the control to open.
If the rollout control has opened, the circuit between the igni-
tion control and gas valve will be interrupted and the ignition
control module will go into lockout. The servicer should reset
the ignition control by opening and closing the thermostat cir-
cuit. The servicer should look for the ignitor arcing which indi-
cates there is power to the ignition control. The servicer should
measure the voltage between each side of the rollout control
and ground while the ignition control is try to power the gas
valve.
VOLT / OHM
METER
RED
RESET
BUTTON
COLOR
IDENTIFYING
TAB
CHECKING FLAME ROLLOUT SWITCH
Auxiliary Limit and Rollout Limit Operation DSI Systems
If the auxiliary limit and/or rollout limit switch opens, the circuit
to the gas valve will be broken and the gas valve will be de-
energized. The control will recognize this as a loss of flame
and will make an ignition attempt. If the limit switch is still
open, the gas will not be energized for the ignition attempt and
ignition will fail. The ignition control will make two additional
ignition attempts and lock out due to failed ignition. The diag-
nostic LED will flash an error code of "1" to indicate the control
has locked out due to failed ignition.
Servicing procedure with unit not firing.
1. Confirm that the outer door was in place and all screws
tightened. (No leaks under the door.)
2. Check to see if any damage was done to the unit espe-
cially the wiring.
3. Confirm that heat exchanger is not obstructed by feeling
for discharge air from the flue hood when the combustion
blower is running but the unit is not firing.
If the preceding steps do not suggest the reason the control
has tripped the unit should be operated as shown below.
1. Remove the heating compartment door.
2. Turn off the power or open the thermostat circuit.
3. Reset the rollout control.
4. Turn power on and put the unit into a call for heating.
Flame rollout could occur. Keep face and hands a
safe distance from burner area.
5. Look under the heat shield as the unit is running. Flames
should be drawn into firing tubes.
a. If only one burner flame is not drawn into the tube,
that tube is restricted.
b. If, without the air circulation blower running, all flames
are not drawn into the tubes either the collector box,
combustion blower, or flue outlet is obstructed. If
the combustion blower or flue outlet is obstructed,
the pressure switch should have opened preventing
the unit from firing, also inspect the unit pressure
switch and wiring.
c. If the burner flame is not drawn into the tube when
the air circulation blower is running, then a cracked
heat exchanger tube may be present.