Bryant Furnace 333BAV User Manual

service and  
333BAV  
333JAV  
Series B  
maintenance procedures  
UPFLOW/HORIZONTAL,  
VARIABLE-SPEED, 2-STAGE,  
INDUCED-COMBUSTION FURNACES  
Cancels: SP04-43  
SP04-50  
10-97  
NOTE: Read the entire instruction manual before performing any  
service or maintenance.  
This symbol indicates a change since the last issue.  
These procedures are for size 60,000 through 120,000 Btuh units.  
Index  
Page  
SAFETY CONSIDERATIONS.....................................................1  
ELECTROSTATIC DISCHARGE (ESD) PRECAUTIONS  
PROCEDURE...........................................................................2  
CARE AND MAINTENANCE..................................................2-5  
Air Filter Arrangement..........................................................2-3  
Blower Motor and Wheel.........................................................3  
Cleaning Heat Exchanger......................................................3-5  
Electrical Controls and Wiring.................................................5  
Troubleshooting ........................................................................5  
Application Wiring Diagrams ..................................................6  
Unit Wiring Diagram................................................................7  
Service Label ............................................................................8  
Troubleshooting Guide .............................................................9  
A95137  
Fig. 1—Model 333BAV or 333JAV Horizontal  
®
SAFETY CONSIDERATIONS  
ama  
Installing and servicing heating equipment can be hazardous due to  
gas and electrical components. Only trained and qualified person-  
nel should install, repair, or service heating equipment.  
Untrained personnel can perform basic maintenance functions  
such as cleaning and replacing air filters. All other operations must  
be performed by trained service personnel. When working on  
heating equipment, observe precautions in the literature, tags, and  
labels attached to or shipped with the unit and other safety  
precautions that may apply.  
CANADIAN GAS ASSOCIATION  
A PPROVED  
R
Follow all safety codes. In the United States, follow all safety  
codes including the National Fuel Gas Code NFPA No. 54-  
1996/ANSI Z223.1-1996. In Canada, refer to the current edition of  
the National Standard of Canada CAN/CGA-B149.1- and .2-M95  
Natural Gas and Propane Gas Installation Codes. Wear safety  
glasses and work gloves. Have fire extinguisher available during  
start-up and adjustment procedures and service calls.  
A94085  
Fig. 2—Model 333BAV or  
333JAV Upflow  
CERTIFICATION OF  
MANUFACTURING SITE  
Recognize safety information. This is the safety-alert symbol  
.
When you see this symbol on the furnace and in instructions or  
manuals, be alert to the potential for personal injury.  
WARNING: The ability to properly perform mainte-  
nance on this equipment requires certain expertise, me-  
chanical skills, tools, and equipment. If you do not  
possess these items, do not attempt to perform any  
maintenance on this equipment other than those proce-  
dures recommended in the User’s Manual. A FAILURE  
TO FOLLOW THIS WARNING COULD RESULT IN  
POSSIBLE DAMAGE TO THIS EQUIPMENT, SERI-  
OUS PERSONAL INJURY, OR DEATH.  
Understand the signal words DANGER, WARNING, and CAU-  
TION. These words are used with the safety-alert symbol. DAN-  
GER identifies the most serious hazards which will result in severe  
personal injury or death. WARNING signifies a hazard which  
could result in personal injury or death. CAUTION is used to  
identify unsafe practices which would result in minor personal  
injury or product and property damage.  
—1—  
 
TABLE 1—UPFLOW/HORIZONTAL FILTER SIZE INFOR-  
MATION (IN.)  
Clean as follows:  
1. Remove blower access door.  
FILTER SIZE†  
Side Return Bottom Return  
FURNACE  
CASING WIDTH  
FILTER  
TYPE  
2. Disconnect blower electrical leads from motor. Squeeze  
latches to remove connectors from motor. Disconnect green  
ground wire from screw. Note location of wires for reas-  
sembly.  
14-3/16  
21  
(1) 16 X 25 X 1* (1) 14 X 25 X 1 Cleanable  
(1) 16 X 25 X 1 (1) 20 X 25 X 1* Cleanable  
(2) 16 X 25 X 1* (1) 24 X 25 X 1 Cleanable  
24-1/2  
3. Remove control.  
* Factory-provided with the furnace.  
† Filters may be field modified as required by cutting and folding the frame as  
indicated on the filter.  
4. Remove screws holding blower assembly to blower deck  
and slide blower assembly out of furnace.  
a. Turn off electrical supply before removing blower and  
control access doors.  
5. Mark blower wheel, motor, and motor support in relation to  
blower housing before disassembly to ensure proper reas-  
sembly.  
b. Release filter retainer from clip at front of furnace  
casing. (See Fig. 4.) For side return, clips may be used  
on either or both sides of the furnace.  
6. Loosen setscrew(s) holding blower wheel on motor shaft.  
MOUNTING  
SCREWS  
7. Remove bolts holding motor and motor mount to blower  
housing and slide motor and mount out of housing. Motor  
mount belly band need not be removed unless motor is to be  
replaced.  
DRAFT  
SAFEGUARD  
SWITCH  
CAUTION: The blower wheel should not be dropped or  
bent as balance will be affected.  
RELIEF  
BOX  
PRESSURE  
SWITCHES  
MAIN  
LIMIT  
SWITCH  
8. Remove blower wheel from housing.  
a. Mark cutoff plate location to ensure proper reassembly.  
b. Remove screws holding cutoff plate and remove cutoff  
plate from housing.  
c. Lift blower wheel from housing through opening.  
MANUAL  
RESET  
9. Clean blower wheel and motor using a vacuum with soft  
brush attachment. Do not remove or disturb balance weights  
(clips) on blower wheel blades.  
LIMIT  
SWITCHES  
10. Reinstall blower wheel by reversing items 8 a through c. Be  
sure wheel is positioned for proper rotation.  
AIRFLOW  
SELECTOR  
11. Reassemble motor and blower by reversing items 4 through  
7.  
CONTROL  
WASHABLE  
FILTER  
CAUTION: Be sure the motor is properly positioned in  
the blower housing. The motor arrow must point in the  
direction of airflow through the furnace after the blower  
assembly has been reinstalled in the furnace.  
FILTER  
RETAINER  
12. Reinstall blower assembly in furnace.  
A95270  
13. Reinstall control. If motor has ground wire, be sure it is  
connected as before.  
Fig. 4—Upflow/Horizontal Component Identification  
c. Slide filter out.  
14. Connect blower electrical leads to motor. Please note that  
connections are polarized for assembly. DO NOT FORCE.  
d. Clean filters by spraying tap water through filter from  
opposite direction of airflow.  
15. If power choke is attached to blower housing, ensure it is  
connected in series with black power lead to motor.  
e. Rinse and let dry. Oiling or coating of filter is not  
recommended or required.  
C. Cleaning Heat Exchanger  
f. Place filter in furnace.  
The following steps should be performed by a qualified service  
technician:  
g. Replace blower and control access doors and turn on  
electrical supply to furnace.  
NOTE: Deposits of soot and carbon indicate the existence of a  
problem which needs to be corrected. Take action to correct the  
problem.  
B. Blower Motor and Wheel  
For long life, economy, and high efficiency, clean accumulated dirt  
and grease from the blower wheel and motor annually.  
The following steps should be performed by a qualified service  
technician:  
The motors have prelubricated sealed bearings and require no  
lubrication.  
If it becomes necessary to clean the heat exchanger because of  
carbon deposits, soot, etc., proceed as follows:  
1. Turn gas and power to furnace to OFF.  
2. Remove control and blower access doors.  
Remember to disconnect the electrical supply before removing  
access doors.  
3. Disconnect wires to the following components. Mark wires  
to aid in reconnection of:  
—3—  
 
a. Draft safeguard switch.  
b. Inducer motor.  
NOTE: Be very careful when removing the burner assembly to  
avoid breaking the ignitor. See Fig. 6 for the correct ignitor  
location.  
c. Pressure switch(es).  
11  
13  
32"  
32"  
d. Limit overtemperature switch(es).  
e. Gas valve.  
BURNER  
f. Hot surface ignitor.  
g. Flame-sensing electrode.  
h. Wiring connectors leading to control.  
CELL  
PANEL  
4. Remove 2 screws that secure relief box. (See Fig. 4.)  
5. Remove 8 screws that secure flue collector box to center  
panel. Be careful not to damage sealant.  
HOT  
SURFACE  
IGNITOR  
ASSEMBLY  
6. Remove complete inducer assembly from furnace, exposing  
flue openings.  
7. Using field-provided small wire brush, steel spring cable,  
reversible electric drill, and vacuum cleaner, clean cells as  
follows:  
a. Assemble wire brush and steel spring cable.  
(1.) Use 48 in. of 1/4-in. diameter high-grade steel  
spring cable (commonly known as drain clean-out  
or Roto-Rooter cable).  
C
IGNITOR  
BURNER  
L
7
(2.) Use 1/4-in. diameter wire brush (commonly known  
as 25-caliber rifle cleaning brush).  
8"  
C
L
NOTE: The materials needed in items (1.) and (2.) can usually be  
purchased at local hardware stores.  
IGNITOR  
ASSEMBLY  
(3.) Insert twisted wire end of brush into end of spring  
cable, and crimp tight with crimping tool or strike  
with ball-peen hammer. TIGHTNESS IS VERY  
IMPORTANT.  
A93347  
Fig. 6—Position of Ignitor to Burner  
(6.) IMPORTANT: Replace screws in center panel to  
secure heat exchanger cells before cleaning.  
(4.) Remove metal screw fitting from wire brush to  
allow insertion into cable.  
(7.) Insert brush end of cable in lower opening of cell,  
and proceed to clean 2 lower passes of cell in same  
manner as 2 upper passes.  
b. Clean each heat exchanger cell.  
(1.) Attach variable-speed, reversible drill to end of  
spring cable (end opposite brush).  
(8.) Repeat foregoing procedures until each cell in  
furnace has been cleaned.  
(2.) Remove cell outlet plates. IMPORTANT: Replace  
screws in center panel to secure heat exchanger  
cells before cleaning.  
(9.) Using vacuum cleaner, remove residue from each  
cell.  
(3.) Insert brush end of cable into upper opening of cell  
and slowly rotate with drill. DO NOT force cable.  
Gradually insert at least 36 in. of cable into 2 upper  
passes of cell. (See Fig. 5.)  
(10.) Using vacuum cleaner with soft brush attachment,  
clean burner assembly.  
(11.) Reinstall cell outlet plates and screws FIRST;  
then, reinstall cell inlet plates and burner assem-  
bly. Care must be exercised to center the burners  
in the cell openings.  
8. After cleaning flue openings, clean flue collector. Check  
sealant on flue collector to ensure that it has not been  
damaged. If new sealant is needed, contact your dealer or  
distributor.  
9. Replace flue collector assembly, making sure all 8 screws  
are secure.  
10. Reinstall relief box.  
11. Reconnect wires to the following components:  
a. Draft safeguard switch.  
b. Inducer motor.  
A91252  
Fig. 5—Cleaning Heat Exchanger Cell  
c. Pressure switches.  
(4.) Work cable in and out of cell 3 or 4 times to obtain  
sufficient cleaning. DO NOT pull cable with great  
force. Reverse drill and gradually work cable out.  
d. Limit overtemperature switch(es).  
e. Gas valve.  
(5.) Remove burner assembly and cell inlet plates.  
f. Hot surface ignitor.  
—4—  
 
g. Flame-sensing electrode.  
The control in this furnace is equipped with an LED status light to  
aid in installation, servicing, and troubleshooting. It can be viewed  
through the sight glass or window on the blower access door. The  
control indicates status with the LED on continuously, rapid  
flashing, or a code composed of 2 digits. (The first digit is the  
number of short flashes, the second is the number of longs flashes.)  
Refer to the service label on the blower compartment door for code  
explanations and useful troubleshooting suggestions. (See Fig. 10.)  
h. Wiring connectors leading to control.  
12. Reconnect vent pipe to relief box.  
13. Replace blower door only.  
14. Turn power and gas to ON.  
15. Set thermostat and check furnace for proper operation.  
16. Verify blower airflow and that airflow rate changes between  
heating and cooling.  
It is important to note that power to the furnace must not be  
interrupted and the furnace blower door must not be removed until  
the LED status code(es) is recorded. When power to the control is  
interrupted, the status memory is erased.  
17. Check for gas leaks.  
18. Replace control door.  
The control will store up to 5 previous codes but will not store  
non-current codes longer than 48 hr. To retrieve previous codes, if  
present, no thermostat inputs to the control must be present and all  
time delays must expire. Remove 1 of the red main limit wires 1  
to 4 sec until the LED light goes out, then reconnect it. (See Fig.  
4.) (Do not leave red wire disconnected for longer than 4 sec as the  
control will assume an overtemperature condition exits and will  
respond with indoor blower operation.) This places the control in  
the status recall mode and displays the first code stored in memory.  
Record the code and repeat the disconnect and reconnect of the red  
wire, recording each code until code 11 is displayed indicating no  
additional faults. After the last code is displayed or after 2 minutes  
in the code recall mode, the control will return to normal standby  
mode.  
WARNING: Never use a match or other open flame to  
check for gas leaks. Use a soap-and-water solution. A  
failure to follow this warning could result in fire, personal  
injury, or death.  
D. Electrical Controls and Wiring  
NOTE: There may be more than 1 electrical supply to unit.  
The electrical ground and polarity for 115-v wiring must be  
maintained properly. Refer to Fig. 7 and 8 for field wiring  
information and to Fig. 9 for unit wiring information. If the  
polarity is NOT correct, the furnace control will display rapid  
flashing on the status LED and prevent heat operation. The control  
system also requires an earth ground for proper operation of the  
microprocessor and variable-speed motor.  
Use any recorded status codes, the service label, and the trouble-  
shooting diagram on the following pages to diagnose and correct  
any problem condition.  
NOTE: Be aware that measurement of current (amperes) and  
power (watts) for the ICM2+ variable-speed motor will be accurate  
only when the meter provides true root-mean-square (RMS)  
measurements.  
E. Troubleshooting  
Refer to the service label. (See Fig. 10.) Page 9 contains a  
troubleshooting guide. This guide can be a useful tool in isolating  
furnace operation problems. Beginning with the word "Start,"  
answer each question and follow the appropriate arrow to the next  
item.  
With power disconnected from unit, check all electrical connec-  
tions for tightness. Tighten all screws on electrical connections. If  
any smoky or burned connections are noticed, disassemble the  
connection, clean all parts and stripped wire, and reassemble  
properly and securely. Electrical controls are difficult to check  
without proper instrumentation; therefore, reconnect electrical  
power to unit and observe unit through 1 complete operating cycle.  
The guide will help to identify the problem or failed component.  
After replacing any component, verify correct operation sequence.  
More information is available in a separate Troubleshooting Guide  
for 2-stage gas-fired induced-combustion furnaces.  
The 24-v circuit contains an automotive-type, 3-amp fuse located  
on the main control. Any 24-v electrical shorts during installation,  
service, or maintenance could cause this fuse to blow. If fuse  
replacement is required, use ONLY a 3-amp fuse. The control will  
display code 24 when the fuse needs replacement.  
—5—  
 
FIELD 24-V WIRING  
FIELD 115-, 208/230-, 460-V WIRING  
FACTORY 24-V WIRING  
FACTORY 115-V WIRING  
NOTE 2  
1-STAGE  
THERMOSTAT  
TERMINALS  
W
C
Y
R
G
FIVE  
WIRE  
FIELD-SUPPLIED  
FUSED DISCONNECT  
THREE-WIRE  
HEATING-  
ONLY  
208/230- OR  
460-V  
THREE  
PHASE  
W2  
BLK  
BLK  
COM  
W/W1  
WHT  
WHT  
208/230-V  
SINGLE  
PHASE  
GND  
NOTE 1  
Y/Y2  
115-V FIELD-  
SUPPLIED  
FUSED  
JUNCTION  
BOX  
R
G
GND  
CONTROL  
CONDENSING  
UNIT  
DISCONNECT  
BOX  
NOTE 4  
AFS  
24-V  
TERMINAL  
BLOCK  
Y1  
NOTES: 1. Connect Y/Y2-terminal as shown for proper operation.  
2. Some thermostats require a "C" terminal connection as shown.  
3. If any of the original wire, as supplied, must be replaced, use  
same type or equivalent wire.  
FURNACE  
4. Y1 is not to be connected.  
NOTE 5  
5. Connect O to thermostat-O only for heat pump applications.  
O
A97588  
Fig. 7—Heating and Cooling Application Wiring Diagram  
for Single-Stage Thermostats and/or Single-Speed Condensing Units  
FIELD 24-V WIRING  
FIELD 115-, 208/230-, 460-V WIRING  
FACTORY 24-V WIRING  
FACTORY 115-V WIRING  
NOTE 2  
2-STAGE  
THERMOSTAT  
TERMINALS  
C
W2 W1 Y2  
R
G
Y1  
FIELD-SUPPLIED  
FUSED DISCONNECT  
SEVEN  
WIRE  
FOUR-WIRE  
HEATING-  
ONLY  
208/230- OR  
460-V  
THREE  
PHASE  
W2  
BLK  
WHT  
BLK  
COM  
W/W1  
WHT  
208/230-V  
SINGLE  
PHASE  
NOTE 1  
GND  
C
Y/Y2  
115-V FIELD- JUNCTION  
Y1  
Y2  
SUPPLIED  
FUSED  
BOX  
R
G
GND  
CONTROL  
BOX  
2-SPEED  
DISCONNECT  
CONDENSING  
UNIT  
AFS  
Y1  
24-V  
TERMINAL  
BLOCK  
NOTES: 1. Connect Y1 and Y/Y2 as shown for proper operation.  
2. Some thermostats require a "C" terminal connection as shown.  
3. If any of the original wire, as supplied, must be replaced, use  
same type or equivalent wire.  
FURNACE  
4. Connect O to thermostat-O only for heat pump applications.  
NOTE 4  
O
A97589  
Fig. 8—Heating and Cooling Application Wiring Diagram  
for 2-Stage Thermostats and/or 2-Speed Condensing Units  
—6—  
 
3 2 2 2 9 3 - 1 0 1 R E V . C  
M I D  
1 7 T E N O  
2
3
4
S W  
S W  
S W  
S C H E M A T I C D I A G R A M  
) E N  
P R O S P & A L G A  
( N A T U R A  
B L K  
W H  
B L U  
D
R E  
T
K
L
B
N
R
G
U
L
B
E L  
Y
E L  
Y
N
R
B
E D  
R
K
L
B
O I  
V
T
W H  
T
H
W
N
R
G
B L K  
K
L
B
N
R
O
B L K  
D
R E  
T
W H  
8
2
7 9  
B L K  
Y
G R  
3
1
Y
G R  
B L K  
1 2  
1 0 1 1  
N
G R  
T
W H  
E
F S  
T
W H  
N
B R  
1
B L U  
6
3
1
2
)
S E U D H E W ( N  
T E N O  
L
Y E  
L
Y E  
9
N
O R  
N
O R  
N
O R  
N
O R  
D
R E  
D
R E  
F
F
O F  
O N  
F
F
O F  
O N  
F
2
O F  
O N  
O F  
O N  
O F  
O N  
4
3
1
M U D E H  
D
R E  
Y E L  
Y E L  
B L U  
Y 1  
B L K  
W H  
U
BL  
T
N
O
R
O
B L K  
B L K  
B L K  
G R  
N
B L U  
R E D  
R E D  
Z E S I  
N
O R  
Y E L  
—7—  
 
WARNING  
Service should be performed only by qualified persons.  
SERVICE  
If status code recall is needed, do not remove power or blower door.  
LED CODE  
STATUS  
CONTINUOUS OFF Check for 115V at L1 and L2, and 24V at SEC1 and SEC2.  
CONTINUOUS ON  
RAPID FLASHING  
Control has 24V power.  
Line voltage polarity reversed. If twinned, 24V power  
to one furnace may be out of phase with power to other furnace.  
EACH OF THE FOLLOWING STATUS CODES IS A TWO-DIGIT NUMBER WITH  
THE FIRST DIGIT DETERMINED BY THE NUMBER OF SHORT FLASHES AND  
THE SECOND DIGIT BY THE NUMBER OF LONG FLASHES.  
11 NO PREVIOUS CODE - Stored status codes are erased when power (115V or  
24V) to control is interrupted or 48 hours after each fault is cleared.  
12 BLOWER ON AFTER POWER UP - Blower runs for 90 seconds, if unit is  
powered up during a call for heat (R-W/W1 closed). Note: 2-sec. ON-delay.  
13 LIMIT OR FLAME ROLL-OUT (FRS) SWITCH LOCKOUT - Auto-reset after  
three hours. FRS switch requires manual-reset.  
Check for: - Refer to #33  
14 IGNITION LOCKOUT - Control will auto-reset after three hours. Refer to #34.  
21 GAS HEATING LOCKOUT - Control will NOT auto-reset.  
Check for: - Mis-wired gas valve  
- Defective control (valve relay)  
22 ABNORMAL FLAME-PROVING SIGNAL - Flame is proved while gas valve is  
de-energized. Inducer will run until fault is cleared.  
Check for: - Leaky gas valve  
- Stuck-open gas valve  
23 LOW- OR HIGH-HEAT PRESSURE SWITCH DID NOT OPEN  
Check for: - Obstructed pressure tubing  
- Defective pressure switch (stuck closed)  
24 SECONDARY VOLTAGE FUSE IS OPEN  
Check for: - Short-circuit in secondary voltage (24V) wiring  
31 HIGH-HEAT PRESSURE SWITCH OR RELAY DID NOT CLOSE OR  
REOPENED  
Check for: -Control relay may be defective - Refer to #32  
32 LOW-HEAT PRESSURE, DRAFT SAFEGUARD , OR AUX-LIMIT  
(DOWNFLOW ONLY*) SWITCH DID NOT CLOSE OR REOPENED  
Check for: - Proper vent sizing (and condensate pitch with side-wall vent)  
- Low inducer voltage (115v)  
- Defective inducer motor  
- Excessive wind  
* Blower motor and capacitor  
- Defective pressure switch  
- Restricted vent  
- Inadequate combustion air supply  
- Disconnected or obstructed pressure tubing  
33 LIMIT OR FLAME ROLL-OUT (FRS) SWITCH IS OPEN - FRS switch  
requires manual-reset.  
Check for: - Inadequate combustion air supply (FRS switch only)  
- Dirty filter or restricted duct system  
- Defective switch or connections  
- Loose blower wheel  
- Blower motor or capacitor failure  
34 IGNITION-PROVING FAULT - Control will retry three times before lockout #14.  
Check for: - Oxide buildup on flame-proving sensor (clean with fine sandpaper).  
- Proper flame-proving microamps (0.5 minimum)  
- Proper control ground continuity  
- Flame-proving sensor must be ungrounded  
- Smooth flame carryover and ignition  
- Manual valve(s) OFF  
43 LOW-HEAT PRESSURE, DRAFT SAFEGUARD, OR AUXILIARY LIMIT  
SWITCH OPEN WHILE HIGH-HEAT PRESSURE SWITCH IS CLOSED  
Check for: - Disconnected or obstructed pressure tubing  
- Defective pressure switch (stuck open)  
- Refer to #32 and #33  
45 REPLACE CONTROL  
320893-101 REV. A  
A94169  
Fig. 10—Service Label  
—8—  
 
TROUBLESHOOTING  
GUIDE  
NOTES:  
WARNING  
!
1. Refer to information label on blower compartment door  
for procedure for use of LED status codes and problem  
solving suggestions.  
2. LED indicator is viewed through window in blower  
compartment door.  
ELECTRICAL SHOCK HAZARD  
3. If 115-vac power is de-energized or interrupted during  
a call for heat, the indoor blower will run for 90 sec  
before a gas heating cycle begins – Code 12.  
4. After replacing any component, verify correct operating  
sequence.  
ONLY QUALIFIED AND TRAINED  
SERVICE PERSONNEL SHOULD  
PERFORM THIS PROCEDURE  
If LED is flashing rapidly, check line voltage polarity.  
If Code 24 is displayed, check for blown fuse.  
If LED is OFF, check line voltage and 24-v transformer.  
If Code 45 is displayed, replace control.  
START  
24v should be present across R  
and C. If not, check for:  
1. Open flame rollout switch  
(FRS) – Code 33.  
2. Open limit switch (LS) –  
Code 33.  
Yes  
Turn thermostat OFF.  
Is indoor blower on ?  
No  
On furnace control, note current  
settings for setup switches 1 (SW-1)  
and 2 (SW-2) then set SW-1 to OFF  
and SW-2 to ON.  
24v should be present across C and W. If not, check for:  
1. Open thermostat.  
2. Open 24-v fuse (FU1) – Code 24.  
3. Failed transformer.  
3. Check all low-voltage wiring  
connections.  
No  
If Code 23 is displayed, the pressure switch(es) is stuck closed.  
Replace switch and/or check pressure tube for blockage.  
Cycle 115-v power  
off for 3 sec, then on.  
No  
Replace control only if all checks  
are OK.  
System malfunction – Code 21.  
115v should be present at the inducer motor. If so, replace inducer  
motor. If not, check 115-v wiring.  
No  
Continuous LED?  
Yes  
If Code 32 is displayed check for:  
1. Open gas inlet pressure switch (when used).  
2. Open pressure switch (LPS) and/or tube – Code 32.  
3. Open draft safeguard switch (DSS) – Code 32.  
4. Open auxiliary switch (ALS)(downflow only) – Code 32.  
5. Check all low-voltage wiring connections.  
Set thermostat to call for heat.  
Set FAN to AUTO.  
No  
Replace control only if Code 45 is  
displayed, or if all checks are OK.  
No  
Draft inducer motor starts.  
115v should be present at the ignitor. If so, replace the ignitor; if not,  
check 115-vac wiring to ignitor.  
Yes  
LPS, DSS, or ALS open while HPS is closed (high-gas-heat only) –  
Code 43.  
No  
Is Code 22 displayed?  
Yes  
Control will attempt to light burners 4 times (approximately 1 minute  
between attempts – Code 34). Voltage is present at the gas valve for 7  
sec during each ignition trial. System will lockout after 4 attempts.  
Flame present when not normal.  
Replace gas valve.  
Is the gas valve control knob in the OPEN or ON position?  
24v should be present across the gas valve terminals C and M/P  
(and C and HI for high-stage test) during the 7 sec ignition trial. If  
not, check all low-voltage wiring connections to valve.  
15-sec inducer pre-purge.  
Yes  
If 24v are present, and main gas does not flow:  
1. Is supply pressure between 4.5- and 13.6-in. wc? If not,  
adjust supply pressure.  
2. If supply pressure is between 4.5- and 13.6-in. wc, replace  
gas valve.  
No  
Replace control only if Code 45 is  
displayed, or if all checks are OK.  
No  
Ignitor warms up and glows  
orange/yellow; 17-sec warm-up.  
Yes  
Check ignitor position.  
No  
Main burners ignite.  
Check burner carryover gap.  
Check manifold pressure (1.3- to 1.7-in. wc for low-stage gas  
heat; 3.2- to 3.8-in. wc for high-stage gas heat).  
Yes  
Check for proper orifice size.  
Is Code 31 (high-gas-heat only), 32, 33, or 34 displayed? Check  
code information label to diagnose.  
Replace control if Code 45 is dis-  
played, or if all checks are OK.  
Clean flame sensor if microamps  
are below nominal.  
No  
No  
Check polarity of 115-v power at J-box and control – Rapid  
flashing LED.  
Main burners stay on.  
Yes  
Check ground continuity from J-box to control.  
Check flame sensor microamps (4.0 nominal; 0.5 minimum for  
control to recognize flame).  
Indoor blower motor starts on  
heating speed after 45-sec  
warm-up period.  
No  
See 2-Stage Gas-Fired Induced-Combustion Furnaces  
Troubleshooting Guide (PSC and ICM Blower Motors).  
Yes  
If not, check for:  
1. Satisfied thermostat.  
2. Open inlet gas pressure switch (when used).  
3. Open pressure switch (LPS) – Code 32.  
4. Open draft safeguard switch (DSS) – Code 32.  
5. Open auxiliary limit (ALS)(downflow only) – Code 32.  
6. Open 24-v fuse (FU1) – Code 24.  
7. Open limit switch (LS) – Code 13 or 33.  
8. Open flame rollout switch (FRS) – Code 13 or 33.  
9. Check 115-v line voltage – LED off.  
No  
No  
No  
Furnace runs until call for  
heat ends.  
No  
Replace control only if Code 45 is  
displayed, or if all checks are OK.  
Yes  
Turn thermostat to OFF; gas valve  
shuts off burners; 5-sec inducer  
post purge.  
Check for sources of electrical noise interference (electronic air  
cleaners, nearby TV, or radio antennas).  
Yes  
Indoor blower motor stops after  
90, 135, 180, or 225 sec.  
If inducer and burners continue to operate, check for 24v at the  
gas valve. If 24v are present, verify that the thermostat is open  
across R and W. If no voltage is present, turn the gas valve  
control knob to the OFF position. Replace gas valve.  
No  
No  
Replace control only if Code 45 is  
displayed, or if all checks are OK.  
Yes  
Heating sequence of operation  
complete. Remove blower door,  
move setup switch 1 (SW-1) to ON  
position and repeat process to check  
high-stage gas heat operation.  
(When finished return SW-1 and  
SW-2 to original desired settings.)  
24v should be present across R and C. If not, check for:  
1. Open limit switch (LS) – Code 13 or 33.  
2. Open flame rollout switch (FRS) – Code 13 or 33.  
Replace control only if Code 45 is  
displayed, or if all checks are OK.  
24v should not be present across R and G. If so, turn thermostat  
FAN switch to AUTO.  
A96062  
—9—  
 
—10—  
 
—11—  
 
SERVICE TRAINING  
Packaged Service Training programs are an excellent way to increase your  
knowledge of the equipment discussed in this manual, including:  
• Unit Familiarization  
• Installation Overview  
• Maintenance  
• Operating Sequence  
A large selection of product, theory, and skills programs is available, using popular  
video-based formats and materials. All include video and/or slides, plus companion  
book.  
Classroom Service Training plus "hands-on" the products in our labs can mean  
increased confidence that really pays dividends in faster troubleshooting, fewer  
callbacks. Course descriptions and schedules are in our catalog.  
CALL FOR FREE CATALOG 1-800-962-9212  
[ ] Packaged Service Training  
[ ] Classroom Service Training  
A94328  
© 1997 Bryant Heating & Cooling Systems 7310 W. Morris St. Indianapolis, IN 46231  
Printed in U.S.A.  
sp0450  
Catalog No. 5333-301  
—12—  
 

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