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ST9103A
Electronic Fan Timer
INSTALLATION INSTRUCTIONS
APPLICATION
The ST9103A Electronic Fan Timer integrates control of all
burner and circulator fan operations in an oil furnace. This
control is the central wiring point for most of the electrical
components in the furnace. The basic purposes of the
ST9103A are to monitor the thermostat for heat, cool, and fan
demands and run the oil burner primary control and up to a
two-speed circulating fan as required. The ST9103A also
monitors a limit switch string, which energizes the circulating
fan whenever the limit switch opens.
Electronic air cleaner and humidifier convenience terminal
connections may be provided as an option. A means for
operating continuous indoor air circulation is also available as
an option.
SPECIFICATIONS
Electrical Ratings:
Power Requirements:
Voltage: 18-30 Vac, 50/60 Hz.
Current: 4 VA at 24 Vac.
Contact Ratings:
Circulating Fan: 15A Full Load, 30A Locked Rotor at
115 Vac (includes optional EAC load).
On/Off Delay Settings:
Delay On: 30 seconds, fixed.
Delay Off: 60, 90, 120, 150 seconds, field-adjustable.
Timing Tolerance: larger of ±20% or 5 seconds.
2. Check the ratings and specifications given in the
Instructions and on the product to assure the product is
suitable for your application.
3. Installer must be a trained, experienced service
technician.
4. After installation is complete, check out the product
operation as provided in these instructions.
CAUTION
Disconnect power supply before wiring to prevent
electrical shock or equipment damage.
Location and Mounting
The ST9103A is mounted in the appliance wiring
compartment using four No. 6 screws (obtained locally)
through standoffs on the corners of the board.
Wiring
All wiring must comply with local codes and ordinances.
Disconnect power before making wiring connections. Refer to
Fig. 1 for standard wiring connections. Refer to Fig. 2 for an
internal schematic.
Setting the Heat Fan Off Delay Switches
Set the heat fan off delay switches to either 60, 90, 120, or
150 seconds, as shown in Fig. 3. The off delay time starts
when the burner motor is de-energized at the end of a
thermostat call for heat.
CHECKOUT
Envrionmental Ratings:
Temperature: -40 to +150° F [-40° to +66° C].
Humidity: 95% maximun, noncondensing.
INSTALLATION
When Installing this Product...
1. Read these instructions carefully. Failure to follow them
could damage the product or cause a hazardous
condition.
Copyright © 1997 Honeywell Inc. • All Rights Reserved
Assure the system operates properly by operating the system
through at least one complete heating cycle and cooling
cycle, if applicable. Troubleshoot by checking for appropriate
voltages at the ST9103A terminals controlling the burner
motor and heat and cool speed circulating fan. The ST9103A
schematic shows internal switching to clarify operation and
assist in troubleshooting. See Fig. 2.
X-XX UL
69-0771B
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S9103A ELECTRONIC FAN TIMER
STARTING
CAP
FUSE
INTERLOCK
L2 (N)
L1 (H)
TO 120 VAC
POWER SUPPLY
LO
ML
MH
HI
CIRCULATING
FAN
LIMIT
CONTROL
THERMOSTAT
120
VAC
24
VAC
ST9103
UNUSED
3
MOTOR
B
12
U
R
N
E
R
123
C
E
O
A
N
C
T
1
4
5
H
U
M
67
C
H
O
E
O
A
L
T
X
C
BURNER
MOTOR
GYW
R
DENOTES STANDARD TERMINAL.
1
DENOTES OPTIONAL TERMINAL.
NOTE:
DENOTES LINE VOLTAGE CONNECTIONS.
DENOTES LOW VOLTAGE CONNECTIONS.
W
R
G
Y
C
1
Fig. 1. Typical ST9103A wiring connections.
L1
(WHITE)
(BLACK)
OIL PRIMARY CONTROL
L2
ORANGE
R8991
FLAME DETECTOR
CAD CELL
T1 T2
M5551
69-0771B
2
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FUSE
TO 120 VAC
POWER SUPPLY
S9103A ELECTRONIC FAN TIMER
INTERLOCK
ELECTRONIC
AIR CLEANER
S2
K1
K1
CN6-9
K2 HEAT
COOL
K2
CONSTANT
LIMIT
CN6-1
(OPTIONAL)
1
CN6-2 CN6-4
L1
CN6-7
CN6-8
HUM
S1
S3
1
HUMIDIFIER
(OPTIONAL)
ACCESSORY
(OPTIONAL)
1
MED
HIGH
LOW
M1
M2
R8991
OIL PRIMARY
CONTROL
BURNER
MOTOR
120 VAC
MED-HIGH
1
L2
N4
CN6-5
N7
N6
CIRCULATION
BLOWER
N3
N1
N2
C
ST9103A OIL
ELECTRONIC
FAN TIMER
T1 T2
CN6-3
DENOTES OPTIONAL CONNECTIONS, COMPONENTS AND ACCESSORIES.
1
NOTE: DOTTED LINES REPRESENT PRINTED CIRCUIT BOARD WIRING.
R8891
CN6-6
R8991
CONTROL
K3
Fig. 2. ST9103A internal schematic.
24 VAC
X
R8991
LIMIT SENSOR
CIRCULATION
BLOWER
K1 K2
R
W
Y
G
C
THERMOSTAT
M5552
3
69-0771B
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S9103A ELECTRONIC FAN TIMER
UNUSED
3
123
4
5
H
E
A
T
H
U
M
67
X
C
ST9103A
ON
1
2
MOTOR
B
12
U
R
N
E
R
C
C
E
O
O
A
O
N
C
L
T
W
G
ON
1
60 SEC 90 SEC
ON
1
2
DELAY OFF SWITCH SETTINGS
Y
ON
1
120 SEC
C
ON
2
1
2
150 SEC
M5550
R
2
Fig. 3. Setting delay off switches.
ST9103 Operating Sequence.
Action System Response
Thermostat calls for heat.
(W terminal is energized.)
• ST9103A closes oil primary control T-T connections.
• Ignition system and oil primary control start the furnace. Oil flows as long as
oil primary control senses flame.
• Burner motor is energized and heat fan on delay timing begins. When timing
is complete, the circulating fan is energized at heat speed and warm air is
delivered to the controlled space.
Thermostat ends call for heat.
(W terminal is de-energized.)
• Oil primary control is de-energized, terminating the burner cycle.
• Heat fan off delay timing begins. When timing is complete, the circulating
fan is de-energized.
• ST9103A returns to standby mode (oil primary control and circulating
fan are off).
Burner fails to light. • Oil primary control locks out within lockout timing (timing depends on oil
primary control).
• Burner motor is de-energized.
• If heat fan has started, it continues through the selected delay off period.
Established flame fails. • Burner motor is de-energized and oil primary control goes into recycle mode.
• If selected heat fan off delay is longer than the recycle delay timing, the
heat fan continues to run through the next trial for ignition.
Thermostat begins call for cool.
(G and Y terminals are energized.)
Thermostat ends call for cool.
• Circulating fan is energized at cool speed.
• Cooling compressor turns on immediately.
• Circulating fan and cooling compressor turn off immediately.
(G and Y terminals are de-energized.)
Thermostat begins call for fan.
(G terminal is energized.)
• Circulating fan is energized immediately at cool speed.
• ST9103A maybe factory-configured to operate heat speed in this mode.
69-0771B
4
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S9103A ELECTRONIC FAN TIMER
ST9103 Operating Sequence (Continued).
Action System Response
Thermostat ends call for fan.
(G terminal is de-energized.)
Limit switch string opens. • Oil primary control shuts off burner.
Limit switch string closes. • ST9103A begins heat fan off delay sequence.
Continuous circulating fan is connected.
(Optional connectors are available for
separate circulating fan speed tap.)
Electronic air cleaner is connected.
(Optional connectors are available for 120
Vac electronic air cleaner.)
Humidity control is connected.
(Optional connectors are available for 120
Vac humidifier.)
• Circulating fan is de-energized.
• Circulating fan is energized immediately at heat speed.
• ST9103A opens oil primary control T-T connections.
• Circulating fan runs as long as limit string stays open.
• If there is a call for cooling or fan, the circulating fan switches from heat
speed to cool speed.
• Circulating fan turns off after the selected heat fan off delay timing.
• ST9103A recloses oil primary control T-T connections.
• Oil primary control is energized, initiating burner light off.
• Circulating fan is energized at low speed when there is no call for heat,
cool or fan.
• If fan operation is required by a call for heat, cool or fan, the ST9103A
switches off the continuous fan speed tap before energizing the other
fan speed.
• Electronic air cleaner (EAC) connections are energized when the heat or
cool speed of the circulating fan is energized. EAC connections are not
energized when the optional continuous fan terminal is energized.
• Humidifier connections are energized when burner motor is energized.
5
69-0771B
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S9103A ELECTRONIC FAN TIMER
Home and Building Control
Honeywell Inc.
Honeywell Plaza
P.O. Box 524
Minneapolis MN 55408-0524
69-0771B69-0771B G.H. 3-97 Printed in U.S.A.
Home and Building Control
Honeywell Limited-Honeywell Limitée
155 Gordon Baker Road
North York, Ontario
M2H 2C9
6
Helping You Control Your World
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