Honeywell CM921 User Guide

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Honeywell CM921 Thermostat Specification

The Honeywell CM921 Thermostat is a sophisticated, wireless programmable thermostat designed for controlling domestic heating systems with precision and ease. It operates on a single-channel system, making it suitable for managing a single heating zone. The device features a large, backlit LCD display that provides clear visibility of temperature settings and program schedules, ensuring user-friendly interaction.

The CM921 offers a 7-day programming capability, allowing users to set different schedules for each day of the week, which can be customized to fit various lifestyle needs. It supports up to six independent temperature settings per day, providing flexibility and energy efficiency by heating the home only when necessary. The thermostat utilizes TPI (Time Proportional and Integral) advanced technology, enhancing temperature control accuracy and minimizing energy consumption by reducing temperature swings.

Wireless communication between the thermostat and the receiver box is achieved through RF (Radio Frequency) technology, ensuring reliable and interference-free operation. The thermostat communicates with a pre-bound receiver, simplifying the installation process as no wiring between the components is required. The CM921 is powered by two AA batteries, which typically last over a year, and includes a low battery indicator to alert users when a replacement is needed.

Additional features include a holiday mode that allows temporary suspension of the regular heating schedule during extended absences and a frost protection function that prevents the heating system from dropping below a set minimum temperature, safeguarding against freezing conditions. The Honeywell CM921 Thermostat combines advanced technology with user-friendly features, making it a versatile and efficient solution for modern home heating control.

Honeywell CM921 Thermostat F.A.Q.

How do I set the time and date on my Honeywell CM921 thermostat?

To set the time and date, press the 'Date/Time' button. Use the '+' or '-' buttons to adjust the time and date, then press 'OK' to confirm your settings.

What should I do if my Honeywell CM921 is not turning on the heating?

Check if the thermostat is set to the correct mode and temperature. Ensure that the boiler is on and the circuit breaker is not tripped. If the problem persists, consult the user manual or contact a professional.

How can I reset my Honeywell CM921 thermostat to factory settings?

To reset the thermostat, remove the batteries and press any button for 5 seconds. Reinsert the batteries, and the thermostat will reset to factory settings.

Why is my Honeywell CM921 display blank?

If the display is blank, check the batteries and replace them if necessary. Ensure that the batteries are installed correctly.

How do I program the schedule on my Honeywell CM921 thermostat?

Press the ‘Program’ button, select the day or period you want to program, and set the desired time and temperature using the '+' or '-' buttons. Confirm each setting with the 'OK' button.

What does the 'OFF' message on my Honeywell CM921 mean?

The 'OFF' message indicates that the thermostat is in off mode and will not activate the heating system. To turn it back on, press the 'Heating' button and adjust the temperature.

Can I lock the controls on my Honeywell CM921 thermostat?

Yes, you can lock the controls by holding the 'OFF' button for 5 seconds until the lock symbol appears. To unlock, repeat the process.

What maintenance is required for the Honeywell CM921 thermostat?

Regularly check and replace the batteries to ensure the thermostat operates correctly. Keep the thermostat clean and free from dust.

How do I change the batteries in my Honeywell CM921 thermostat?

Slide the battery compartment cover off and remove the old batteries. Insert new AA alkaline batteries, ensuring correct polarity, and replace the cover.

Why does my Honeywell CM921 thermostat show an error code?

Error codes indicate specific issues. Refer to the user manual for the meaning of the code and troubleshooting steps. If unresolved, contact customer support.