Honeywell ST9100S


The Honeywell ST9100S is a central heating timer and programmer. It is designed to provide automatic time and temperature control of domestic central heating systems, ensuring that the desired temperature is reached at the appropriate time. The ST9100S features a backlit display, easy-to-use controls, and a variety of programming options to suit a range of heating requirements. It can be used to control both traditional and combi boilers, and is compatible with a wide range of heating systems.

How to operate

Here are some general steps to help you operate the ST9100S:

  1. Set the clock: The first step is to set the clock. Press the “CLOCK” button, and use the “+” and “-” buttons to set the time and day.
  2. Select the mode: The ST9100S has three modes: Automatic, Off, and On. Press the “MODE” button to select the mode you want to use.
  3. Set the temperature: If you’re using the Automatic mode, you’ll need to set the desired temperature. Press the “SET” button, and use the “+” and “-” buttons to set the temperature you want.
  4. Program the timer: You can program the ST9100S to turn the heating system on and off at specific times. Press the “PROG” button, and use the “+” and “-” buttons to set the on and off times for each day of the week.
  5. Override the timer: If you need to override the timer and turn the heating system on or off outside of the programmed times, press the “BOOST” button. The heating system will run at the desired temperature for one hour.

These are just some general steps for operating the Honeywell ST9100S. For more detailed instructions, please refer to the user manual that came with the unit.


ST9100 user guide

ST9100s installation instructions