Resideo ST9120U Electronic Fan Timer Installation Instructions

Download User Manual for Resideo Technologies ST9120U Universal Electronic Fan Timer [12 pages 69-0644-02 2020 pdf/zip]

SKU: RESIDEOST9120UUM2020 Category: Brand:


Resideo ST9120U Universal Electronic Fan Timer

The ST9120U Universal Electronic Fan Timers integrate control of all combustion blower and circulating fan operations in a gas warm air appliance. This control is the central wiring point for most of the electrical components in the furnace. The basic purposes of the ST9120U are to monitor the thermostat for heat, cool and fan demands, run the induced draft blower motor and run a circulating fan (up to two speeds) as required.
The electronic fan timers also monitor limit switch strings and energize separate ignition control systems through spst pressure switches.

Read these instructions carefully. Failure to follow them could damage the product or cause a hazardous condition.




– Location and Mounting
– Wiring
– Setting Adjustable Heat Fan DIP Switches
– ST9120 to ST9120U Wiring Conversion Instructions
– ST9101 to ST9120U Wiring Conversion Instructions


Table 1. ST9101 to ST9120U Wiring Conversions
Table 2. Recommended Default Dip Switch Settings
Table 3. ST9101 Wire Adapter Connections
Table 4. ST9120U Operating Sequence.

Fig. 1. Typical ST9120U wiring connections with S8600 Intermittent Pilot Ignition Module.
Fig. 2. Typical ST9120U wiring connections with SV9500/SV9501 SmartValve(TM) System Control.
Fig. 3. Typical ST9101 wiring connection in standing pilot system.
Fig. 4. Typical ST9120U wiring connections with wire adapter for replacing ST9101.
Fig. 5. ST9120U internal schematic for Intermittent Pilot application.
Fig. 6. ST9120U internal schematic for SmartValve(TM) System applications.
Fig. 7. ST9101 Wire Adapter Schematic
Fig. 8. Setting heat fan-on, heat fan-off and cool fan-on delay DIP switches.

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