Honeywell ST9400A user manual

Yes, the Honeywell ST9400C programmer does have a battery. It is used to maintain the clock and programming settings in case of a power outage. The battery is built-in and not replaceable by the user. It is designed to last for the life of the programmer.

The Honeywell ST9400A and ST9400C are both programmable timers used for controlling heating systems. However, there are a few key differences between the two models:
1. Mounting Option: The ST9400A is a surface-mounted timer, meaning it is mounted on the wall. The ST9400C, on the other hand, is a backplate-mounted timer, which is typically installed inside the heating system's control panel.
2. Dimensions: The ST9400A is slightly larger in size compared to the ST9400C. The ST9400A measures 150mm x 97mm x 40mm, while the ST9400C has dimensions of 100mm x 75mm x 30mm.
3. Display Type: The ST9400A features a digital LCD display for easy programming and temperature control. In contrast, the ST9400C has a rotary dial and buttons for programming and temperature adjustment.
4. Flexibility: The ST9400C offers more flexible programming options compared to the ST9400A. It allows for different heating schedules for weekdays and weekends, while the ST9400A only offers a single program for each day of the week.
Overall, the main differences between the ST9400A and ST9400C lie in their mounting options, dimensions, display types, and programming flexibility. It is recommended to choose the model that best suits your specific heating system requirements and installation preferences.

On the Honeywell ST9400A programmer, the "Auto" and "Continuous" settings refer to different operating modes:
1. Auto Mode: In this mode, the programmer will automatically switch the heating on and off as per the programmed schedule. It allows you to set specific timings for your heating to turn on and off during different parts of the day or week. For example, you can schedule the heating to turn on in the morning and evening, and off during the night or when you're away.
2. Continuous Mode: This mode allows you to manually override the programmed schedule and keep the heating system running continuously. If you select the continuous mode, the heating will remain on constantly until you manually switch it off or switch back to the "Auto" mode.
So, the difference between the "Auto" and "Continuous" settings on the Honeywell ST9400A is that "Auto" follows the programmed schedule, while "Continuous" keeps the heating on continuously until manually turned off.