Honeywell CM921 manual How do I set one temperature for the whole day?, What is Optimum Start?

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fAq’s & TRoublESHooTING

How do I change the batteries on the CM921 when they run out?

The thermostat constantly monitors the battery power level, which typically last for about 2 years before needing replaced. When the power is running low a lashing symbol will be displayed on the screen. To change the batteries follow the steps in the above section (‘STEP 1: Installing the Batteries’ on page 3), replacing the used batteries with new ones in step c.

Note: While changing the batteries your program settings will be stored but you may need to adjust the time and date settings to be correct.

How do I set one temperature for the whole day?

To operate as a simple thermostat with one temperature for a period of time, move the slider switch to the MAN position. Adjust the manual temperature by pressing the or buttons. This can be set anywhere from 5°C to 35°C in 0.5°C steps. The thermostat will continue to maintain this temperature until another operating mode is selected or the temperature is adjusted.

What is Optimum Start?

Optimum Start is a program which ensures that the optimum temperature conditions are achieved at the required times. This is an Energy Eficiency feature that adjusts the start time of your heating system depending upon how cold it is. For example, on cold days your heating system will be started earlier to ensure that your home is warm when you get up (at the target temperature) and on warmer days the heating system will be started later to save energy. So, if the Optimum Start Feature is used, then the time / temperature settings which are entered into the thermostat should be set to when you want to be warm by and not when you want the heating system to start.

I want to use the table stand instead of wall mounted bracket. Where can I position the room unit?

It is important to keep the room unit in a location where reliable RF communication was proven. Advise your installer where would you like to position the room unit and he will check if the RF communication is reliable in the selected location(s).

Important: The Room Unit measures the temperature of the room where it is located. It is important that the placement of the Room Unit within the room is away from; draughts, direct sunlight and other heat sources. As this is a wireless device certain objects could interfere with the RF signal - Leave at least 30cm distance from any metal objects (including wall boxes) and at least 1 metre from any other electrical equipment eg. radio, TV, PC, etc.

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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 To set the Holiday function Using the Special FunctionsTemperature Override 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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