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
Voltage: 18-30 Vac, 50/60 Hz.
Current: 4 VA at 24 Vac.
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.
Temperature: -40 to +150° F [-40° to +66° C].
Humidity: 95% maximun, noncondensing.
When Installing this Product...
1. Read these instructions carefully. Failure to follow them
could damage the product or cause a hazardous
Copyright © 1997 Honeywell Inc. • All Rights Reserved
Electronic Fan Timer
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
4. After installation is complete, check out the product
operation as provided in these instructions.
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.
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
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.
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.