Introduction
The Resideo ST9120U Universal Electronic Fan Timers are designed to manage the combustion blower and circulating fan operations within gas warm air appliances. These timers serve as a central wiring point for various electrical components in a furnace, monitoring thermostat demands for heat, cool, and fan operations. They are engineered to control the induced draft blower motor and circulating fan, offering adjustable delay settings for heat and cool modes, as well as fixed delays for fan operation.
Key Features and Specifications
- Adjustable heat fan-on and fan-off delays.
- Adjustable cool fan-on delay and fixed cool fan-off delay.
- Supports electronic air cleaner (EAC) and humidifier (HUM) connections.
- Provides continuous low-speed indoor air circulation.
- Electrical ratings: 18 to 30 Vac, 60 Hz.
- Various contact ratings for combustion blower and circulating fan speeds.
Installation Guidance
Proper installation is crucial for the safe and effective operation of the ST9120U. Users are advised to read all instructions carefully before proceeding. Key steps include verifying electrical ratings, ensuring compliance with local codes, and following detailed wiring diagrams provided in the documentation. The manual includes specific conversion instructions for replacing older models like the ST9101, with clear terminal mapping and wiring adapter schematics.
For detailed wiring diagrams and troubleshooting tips, refer to the internal schematics and operating sequence tables within the full document.
