Honeywell CM921 manual Check that there is power to the heating system

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1

Symptom

Possible Cause

Remedy

 

 

 

 

The thermostat’s LCD display

No power to heating system.

Check that there is power to the heating system.

works but the heating does not

 

 

 

switch on (HC60NG LEDs are off

 

 

 

Program does not call for

Move the slider switch to MAN and press

or to

or green one is on).

 

heat.

increase the temperature a few degrees above the

 

 

current room temperature. The heating should come

 

 

on after a few seconds.

 

 

 

 

 

 

Wrong electrical connection.

Call electrical installer to check the boiler and

 

 

 

HC60NG power supply as well as the connection

 

 

between the boiler and the HC60NG.

 

 

 

 

The red LED on the HC60NG is

RF communication lost due

Hook the thermostat back on the wall bracket or

constantly on or lashing.

to the wrong location of the

replace the thermostat on the table stand in the

 

thermostat.

position where RF communication was reliable.

 

 

 

 

 

 

RF communication fault.

Call installer.

 

 

 

NOTE: You can control the boiler manually when the RF

 

 

communication is lost: Press the HC60NG push button

 

 

to switch the boiler on and off. When the green LED is

 

 

on – the boiler is on.

 

 

 

 

 

Heating switches ON or OFF too

The thermostat not set

Call Installer.

 

slowly or quickly.

correctly for your system.

 

 

 

 

 

 

Temperature swings between

The thermostat not set

Call Installer.

 

too hot and too cold.

correctly for your system.

 

 

 

 

 

 

fAq’s & TRoublESHooTING

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Contents CM921 User Guide Plumbnation.co.uk Controls Layout Installing the Batteries To install the BatteriesTo set the Date and Time Setting the Date and TimeRunning the Built-in Heating Program Modifying the Heating Program Built-in Heating ProgramReviewing the Heating Program To press or buttons Disabling / Enabling Time Periods To disable time periodsTo enable time periods During Normal Operation Choosing the Operating ModeAdjusting the Time Holiday Function Using the Special FunctionsTemperature Override To set the Holiday functionChanging the User Parameters To change any of these user’s parametersIi Reset the built-in program to the factory default Iii Enable or disable summer/winter time changeTroubleshooting Guide Symptom Possible Cause RemedyCheck that there is power to the heating system How do I set one temperature for the whole day? What is Optimum Start?Wall bracket HC60NG Relay Box Controls LayoutCan I use my CM921 to control my air-conditioning system? An explanation for householders Following explanation applies to heating applications only42011077-103 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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