service and
394HAD
396HAD
Series C
maintenance procedures
GAS-FIRED
INDUCED-COMBUSTION FURNACES
Cancels: SP04-13
SP04-19
11-1-93
NOTE: Read the entire instruction manual before starting the
installation.
→ These procedures are for sizes 65,000 through 150,000 Btuh units.
CANADIAN GAS ASSOCIATION
ama
®
Index
Page
A PPROVED
R
SAFETY CONSIDERATIONS.....................................................1
CARE AND MAINTENANCE..................................................1-5
Air Filter Arrangement..........................................................2-3
Blower Motor and Wheel......................................................3-4
Cleaning Heat Exchanger......................................................4-5
Electrical Controls and Wiring.................................................5
Pilot ...........................................................................................5
Troubleshooting ........................................................................5
Unit Wiring Diagram ............................................................6-7
Troubleshooting Chart ..............................................................8
SAFETY CONSIDERATIONS
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, on tags,
and on labels attached to or shipped with the unit and other safety
precautions that may apply.
A92058
Fig. 1—Model 396HAD
Downflow
Follow all safety codes. In the United States, follow all safety
codes including the National Fuel Gas Code NFPA No. 54-
1992/ANSI Z223.1-1992 (NFGC). In Canada, refer to the current
edition of the National Standard of Canada CAN/CGA-B149.1-
and .2-M91 Natural Gas and Propane Gas Installation Codes
(NSCNGPIC). Wear safety glasses and work gloves. Have fire
extinguisher available during start-up and adjustment procedures
and service calls.
A92057
Fig. 2—Model 394HAD Upflow
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, do not attempt to perform any maintenance
on this equipment other than those procedures recom-
mended in the User’s Manual. FAILURE TO FOLLOW
THIS WARNING COULD RESULT IN POSSIBLE
DAMAGE TO THIS EQUIPMENT, SERIOUS PER-
SONAL INJURY, OR DEATH.
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.
Understand the signal word DANGER, WARNING, or 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 that 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. NOTE is used to highlight sugges-
tions that will result in enhanced installation, reliability, or
operation.
CARE AND MAINTENANCE
For continuing high performance and to minimize possible equip-
ment failure, it is essential that periodic maintenance be performed
on this equipment. Consult your local dealer as to the proper
frequency of maintenance and the availability of a maintenance
contract.
—1—
MOUNTING
SCREWS
DRAFT
SAFEGUARD
SWITCH
AUXILIARY
LIMIT SWITCH
(NOT VISIBLE)
FLUE
COLLECTOR
BOX
RELIEF
BOX
SPEED
SELECTOR
VENT PIPE
ENCLOSURE
GAS
VALVE
MOUNTING
SCREWS
CONTROL
BOX
PILOT
DRAFT
SAFEGUARD
SWITCH
CONTROL
BOX
RELIEF
BOX
SPEED
SELECTOR
FLUE
COLLECTOR
BOX
FILTER
RETAINER
WASHABLE
FILTER
A92178
A92179
Fig. 4—Model 394HAD Upflow
b. Remove blower and control access doors.
Fig. 5—Model 396HAD Downflow
3. Disconnect wires from auxiliary limit on blower housing
(downflow furnace only).
c. 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.
4. Remove control box.
5. Remove electrical leads from numbered side of blower
speed selector. (See Fig. 4 and 5.) Note location of wires for
reassembly.
d. Slide filter out.
e. Furnaces are equipped with permanent, washable filters.
Clean filters with tap water. Spray water through filter in
opposite direction of airflow.
6. Remove screws holding blower assembly to blower deck
and slide blower assembly out of furnace.
f. Rinse and let dry. Oiling or coating of filter is not
recommended or required.
7. Squeeze side tabs of blower speed selector and pull it out of
blower housing.
g. Reinstall filter.
8. Loosen screw in strap holding motor capacitor to blower
housing and slide capacitor out from under strap.
h. Replace access doors.
i. Restore electrical power to furnace.
9. Mark blower wheel, motor, and motor support in relation to
blower housing before disassembly to ensure proper reas-
sembly.
B. Blower Motor and Wheel
For long life, economy, and high efficiency, clean accumulated dirt
and grease from the blower wheel and motor annually.
10. Loosen setscrew holding blower wheel on motor shaft.
11. Remove bolts holding motor mount to blower housing and
slide motor and mount out of housing. Disconnect ground
wire attached to blower housing before removing motor.
The following steps should be performed by a qualified service
technician:
Some motors have prelubricated sealed bearings and require no
lubrication. These motors can be identified by the absence of oil
ports on each end of the motor. For those motors with oil ports,
lubricate motor every 5 years if motor is used on intermittent
operation (thermostat FAN switch in AUTO position), or every 2
years if motor is in continuous operation (thermostat FAN switch
in ON position).
12. Lubricate motor (when oil ports are provided).
a. Remove dust caps or plugs from oil ports located at each
end of motor.
b. Use a good grade of SAE 20 nondetergent motor oil and
put 1 teaspoon, 5 cc, 3/16 oz, or 16 to 25 drops in each
oil port. Do not over-oil.
Remember to disconnect the electrical supply before removing
access doors.
c. Allow time for total quantity of oil to be absorbed by
each bearing.
Clean and lubricate as follows:
d. Wipe excess oil from motor housing.
e. Replace dust caps or plugs on oil ports.
1. Remove 2 screws from blower access door (downflow
furnace only). Remove blower access door.
13. Remove blower wheel from housing.
2. Remove vent pipe enclosure (downflow furnace only) and
disconnect short piece of vent pipe from relief box.
a. Mark cutoff location to ensure proper reassembly.
—3—
b. Remove screws holding cutoff plate and remove cutoff
plate from housing.
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. Lift blower wheel from housing through opening.
14. Clean blower wheel and motor using a vacuum cleaner with
soft brush attachment. Do not remove or disturb balance
weights (clips) on blower wheel blades. The blower wheel
should not be dropped or bent as balance will be affected.
(2.) Use 1/4-in. diameter wire brush (commonly known
as 25-caliber rifle cleaning brush).
NOTE: The items needed in steps (1.) and (2.) can usually be
purchased at local hardware stores.
15. Reinstall blower wheel by reversing steps 13 a. through c.
Be sure wheel is positioned for proper rotation.
(3.) Insert twisted wire end of brush into end of steel
spring cable, and crimp tight with crimping tool or
strike with ball-peen hammer. TIGHTNESS is very
important.
16. Reassemble motor and blower by reversing steps 5 through
11. If motor has ground wire, be sure it is connected as
before.
(4.) Remove metal screw fitting from wire brush to
allow insertion into cable.
CAUTION: Be sure the motor is properly positioned in
the blower housing. The motor oil ports must be at a
minimum of 45° above the horizontal centerline of the
motor after the blower assembly has been reinstalled in
the furnace.
b. Clean each heat exchanger cell.
(1.) Attach variable-speed, reversible drill to end of
steel spring cable (end opposite brush).
(2.) 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. 6.)
17. Reinstall blower assembly in furnace. Connect electrical
leads to blower speed selector. Please note that connections
are polarized for assembly. DO NOT FORCE.
18. Reinstall control box.
19. Reconnect wires to auxiliary limit switch on blower housing
(downflow furnaces only).
20. Reinstall vent pipe and enclosure (downflow furnaces
only).
21. Turn on electrical power and check for proper rotation and
speed changes between heating and cooling.
22. Replace blower access door and secure with 2 screws
(downflow furnace only).
C. Cleaning Heat Exchanger
The following steps should be performed by a qualified service
technician:
A91252
Fig. 6—Cleaning Heat Exchanger Cell
NOTE: Deposits of soot and carbon indicate the existence of a
problem which needs to be corrected. Take action to correct the
problem.
(3.) 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.
If it becomes necessary to clean the heat exchanger because of
carbon deposits, soot, etc., proceed as follows:
(4.) Remove burner assembly and cell inlet plates.
1. Turn off gas and electrical power to furnace.
(5.) Replace screws in center panel and cells before
cleaning.
2. Remove 2 screws from blower access door (downflow
furnace only). Remove control and blower access doors.
(6.) 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.
3. Remove vent pipe enclosure (downflow furnace only) and
disconnect vent pipe from relief box.
4. Remove 2 screws that secure relief box. (See Fig. 4 or 5.)
(7.) Repeat foregoing procedures until each cell in
furnace has been cleaned.
5. Disconnect wires to the following components:
a. Draft safeguard switch
(8.) Remove residue from each cell using vacuum
cleaner.
b. Inducer motor
(9.) Clean burner assembly using vacuum cleaner with
soft brush attachment.
c. Pressure switch
d. Limit overtemperature switch
e. Gas valve
(10.) Reinstall cell inlet plates and burner assembly.
Care must be exercised to center the burners in the
cell openings.
f. Edge connector leading to control box
6. Remove 8 screws that secure flue collector box to center
panel. Be careful not to damage sealant.
9. After cleaning flue openings, check sealant on flue collector
to ensure that it has not been damaged. If new sealant is
needed, contact your dealer or distributor.
7. Remove complete inducer assembly from furnace, exposing
flue openings.
10. Clean and replace flue collector assembly, making sure all
8 screws are secure.
8. Clean cells using field-provided small wire brush, steel
spring cable, reversible electric drill, and vacuum cleaner.
11. Reinstall 2 screws in relief box.
—4—
12. Reconnect wires to the following components:
a. Draft safeguard switch
PILOT HEAD V–NOTCH FALLS
DIRECTLY BELOW FRONT EDGE
OF BURNER CARRYOVER.
b. Inducer motor
c. Pressure switch
d. Limit overtemperature switch
e. Gas valve
f. Edge connector leading to control box
1
/ ″
8
13. Reconnect vent pipe to relief box. Replace vent pipe
enclosure (downflow furnace only).
14. Replace blower access door only and secure with 2 screws
(downflow furnace only).
15. Turn on electrical power and gas.
16. Set thermostat and check furnace for proper operation.
A91249
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.
Fig. 7—Position of Pilot to Burner
E. Pilot
Check the pilot and clean if necessary at the beginning of each
heating season. The pilot flame should be high enough for proper
impingement of the flame sensing element (or thermocouple) and
to light the burners. Remove the accumulation of soot and carbon
from the flame sensing element (or thermocouple). Refer to Fig. 7
for proper location of pilot on burner assembly.
17. Check for gas leaks.
18. Replace control access door.
D. Electrical Controls and Wiring
NOTE: There may be more than 1 electrical supply to unit.
The electrical ground for 115-v wiring must be maintained
properly. Refer to Fig. 8 for field wiring information and to Fig. 9
for unit wiring information.
F. Troubleshooting
With power disconnected to unit, check all electrical connections
for tightness. Tighten all screws on electrical connections. If any
smoky or burned connections are noticed, disassemble the connec-
tion, 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 24-v circuit contains an automotive-type, 3-amp fuse located
on the main control board. Any direct shorts during installation,
service, or maintenance could cause this fuse to blow. If fuse
replacement is required, use ONLY a 3-amp fuse of identical size.
Page 8 contains a troubleshooting chart. This chart 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.
The chart will help identify the problem or failed component. After
replacing any component, verify correct operating sequence as
indicated by bold arrows.
—5—
FIELD 24-VOLT WIRING
FIELD 115-, 208/230-, 460-VOLT WIRING
FACTORY 24-VOLT WIRING
FACTORY 115-VOLT WIRING
THERMOSTAT
TERMINALS
W
R
G
Y
FOUR
WIRE
FIELD-SUPPLIED
FUSED DISCONNECT
TWO-WIRE
HEATING-
ONLY
208/230- OR
460-VOLT
THREE
PHASE
W
R
BLK
BLK
WHT
WHT
208/230-
VOLT
SINGLE
PHASE
GND
GND
G
AUXILIARY
J-BOX
115-VOLT FIELD-
SUPPLIED
FUSED
DISCONNECT
C
Y
GND
CONTROL
CONDENSING
UNIT
BOX
TWO
24-VOLT
NOTE: If any of the original wire,
as supplied, must be replaced, use
same type or equivalent wire.
WIRE
TERMINAL
BLOCK
NOTE: Connect Y-terminal as
shown for proper
FURNACE
operation.
A78461
Fig. 8—Heating and Cooling Application Wiring Diagram
—6—
Y E L
O R N
B R N
B L U
R E D
R E D
W H T
B L K
R E D
B L U
B L K
B L K
W H T
R E D
W H T
—7—
START
Turn on 115-VAC
power to unit.
Disconnect all thermostat
wires from board.
Turn off 115-VAC
power to unit.
NO
Are
Is 24VAC
across screws
W & C or
all thermostat
wires to board
disconnected?
Is 24VAC
across screws
R & C?
YES
YES
YES
Is blower
running?
G & C?
NO
NO
NO
YES
Check/Replace:
1. Limit switch
Jumper across
screws R & G.
Replace
board.
2. Limit shield (if used)
3. Fuse link
4. Auxillary limit switch (if used)
5. Wire harness
YES
Is
Is
Is
Is
YES
NO
NO
24VAC
115VAC
across HI &
COM?
115VAC
across L1 &
L2?
blower running
on cooling
speed?
across screws
R & C?
YES
YES
NO
NO
Replace
blower motor
and/or start
capacitor.
Check/Replace:
1. Unit power
2. Door switch
3. Power harness
Check/Replace:
1. 3-amp board
fuse
Is
NO
115VAC
Replace
board.
across EAC-1
& COM?
2. Transformer
Check pressure
tube for leak or
YES
Is
24VAC
NO
crimp; otherwise,
Replace
board.
Remove
R & G jumper.
across PL1-2
& screw C on
board?
replace pressure switch
NO
YES
YES
Is heat
exchanger
pressure drop greater
than 0.35-in.
wc?
Is 24VAC
across pressure
switch N/O contact
& screw C on
board?
Repair wire
harness.
Does
blower turn
off?
YES
NO
NO
NO
YES
Check/Replace:
1. Vent systems
2. Induce wheel
Is 24VAC
across pressure
switch N/O contact
& screw C on
board?
YES
Check/Replace:
1. Draft safeguard switch
2. Wire harness
Jumper across
screws R & W.
3. Flue choke
4. Inducer voltage
5. Inducer motor bearings
NO
Check/Replace:
1. Pilot
Is
inducer motor
on?
YES
Is
YES
YES
NO
Is
24VAC across gas
valve?
unit lit?
2. Thermocouple
3. Gas valve
NO
YES
Is
Is
Is
Replace
blower motor
and/or start
capacitor.
blower running
on heat speed 45
sec after unit
lights?
YES
NO
115VAC across
inducer motor
connector?
115VAC across
inducer motor
connector?
Replace
inducer motor.
NO
NO
YES
Is
Is
Is
24VAC
YES
NO
24VAC across
PL-2 & screw
C on board?
115VAC
across EAC-1
& COM?
NO
across
PL-1 & screw
C on board?
Replace
board.
Check/Repair
wire harness;
otherwise,
replace
NO
YES
YES
Check/Replace
thermostat
Replace
board.
Remove
R & M jumper.
Repair wire
harness.
and/or
pressure
thermostat wiring.
switch.
NO
After
NO
YES
off-delay
does blower
turn off?
Reconnect all
thermostat wires.
Does unit
operate?
NOTE: After replacing any component, verify correct operating
YES
sequence as indicated by bold arrows.
END OF TEST.
A91253
© 1993 BDP Co. • P.O. Box 70 • Indianapolis, IN 46206
Printed in U.S.A.
35001b
Catalog No. BDP-3339-432
—8—
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