Honeywell CM921 manual Choosing the Operating Mode, Adjusting the Time, During Normal Operation

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opERATING THE CM921

Choosing the Operating Mode

The thermostat can operate in three different modes: Automatic, Manual or Off. To set the operating mode move the slider switch to the desired position. The screen indicates which mode is currently active by displaying AUTO, MAN or OFF.

•AUTO (automatic) mode

Automatic mode sets the thermostat to follow the temperature program (default or personalised). Operating the thermostat in this mode is the best way to maintain a high level of temperature comfort whilst maximising your energy savings.

•MAN (manual) mode

Manual mode sets the thermostat to act as a simple thermostat with a ixed

setpoint throughout the day. The setpoint can be adjusted from 5°C to 35°C

by using the or buttons. The thermostat will continue to maintain this temperature until another operating mode or temperature is selected.

•OFF mode

Off mode sets the thermostat to control to a minimum temperature setting of 5°C (default) that acts as a frost protection measure for your home. This value can be adjusted by calling your installer.

Adjusting the Time

To adjust only the time during normal operation use the or buttons to adjust

the time and press the green button again to conirm any changes.

During Normal Operation

•Temperature Enquiry

In AUTO and MAN operating modes the thermostat will display the current room temperature, which is indicated by the text ‘ROOM TEMP’ displayed on the

screen. To review the programmed ‘target’ temperature (the temperature which the thermostat is trying to maintain) press the button. This ‘target’ temperature value will be displayed lashing and the text ‘TARGET TEMP’ will be shown for 5 seconds before returning to the current room temperature value.

In OFF operating mode the thermostat again displays the current room temperature, as above, but when the button is pressed the text ‘FROST TEMP’ is displayed indicating the set value to protect your home. To modify this value please contact your installer.



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Contents CM921 User Guide Plumbnation.co.uk Controls Layout To install the Batteries Installing the BatteriesSetting the Date and Time Running the Built-in Heating ProgramTo set the Date and Time Built-in Heating Program Reviewing the Heating ProgramModifying the Heating Program To press or buttons To disable time periods To enable time periodsDisabling / Enabling Time Periods Choosing the Operating Mode Adjusting the TimeDuring Normal Operation Temperature Override Using the Special FunctionsHoliday Function To set the Holiday functionTo change any of these user’s parameters Changing the User ParametersIii Enable or disable summer/winter time change Ii Reset the built-in program to the factory defaultSymptom Possible Cause Remedy Troubleshooting GuideCheck that there is power to the heating system What is Optimum Start? How do I set one temperature for the whole day?HC60NG Relay Box Controls Layout Wall bracketCan I use my CM921 to control my air-conditioning system? Following explanation applies to heating applications only An explanation for householders42011077-103 R1

CM921 specifications

The Honeywell CM921 is a versatile and highly efficient programmable room thermostat designed to enhance comfort and energy management in residential and light commercial applications. This product exemplifies modern heating control technology, making it an excellent choice for users looking to optimize their heating systems while maintaining user-friendly operation.

One of the key features of the CM921 is its ability to program multiple heating schedules. Users can customize settings for different days of the week, allowing for unique heating profiles that can adapt to varying daily routines. This programming capability helps to reduce energy consumption by ensuring that heating is only active when needed, ultimately lowering energy bills.

The CM921 is equipped with an advanced, easy-to-read digital display that provides clear and concise information about the current room temperature and the set temperature. This intuitive interface simplifies user interaction, enabling quick adjustments when necessary. Additionally, the thermostat features a backlit screen, which facilitates usage even in low-light conditions.

Another notable technology integrated into the Honeywell CM921 is its compatibility with various heating systems. It supports both conventional and combi boiler types, making it a flexible solution for diverse heating requirements. The thermostat can also be connected to a 2-wire system, providing an easy installation process and reducing the need for complex wiring modifications.

Energy-saving features are a significant characteristic of the CM921. The thermostat includes an intelligent frost protection setting, which ensures that the temperature does not fall below a pre-defined level when the home is unoccupied for extended periods. This prevents pipes from freezing and potential damage to the system. Furthermore, the device offers a 'holiday mode', allowing users to save energy during extended absences by automatically adjusting the heating schedule.

In terms of characteristics, the Honeywell CM921 boasts a sleek and modern design, ensuring it fits seamlessly into any home décor. Its compact size makes it suitable for installation in various locations, providing flexibility for homeowners.

Overall, the Honeywell CM921 stands out for its blend of advanced technology, user-friendly features, and energy efficiency. It is an ideal solution for anyone seeking to improve their home’s heating management while enjoying comfort and convenience.
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