Honeywell CM921 manual Troubleshooting Guide, Symptom Possible Cause Remedy

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12

Troubleshooting Guide

Symptom

Possible Cause

Remedy

 

 

 

 

 

 

 

 

The thermostat has a blank LCD

Batteries not installed.

Check to see if there are batteries in the battery

screen.

 

compartment and the paper tab has been removed.

 

 

 

 

 

 

 

 

 

Incorrect battery orientation.

Check that the batteries have been installed in the

 

 

 

 

correctorientation.

 

 

 

 

 

 

 

 

 

 

Exhausted batteries.

Replace with new batteries.

 

 

 

 

 

 

The thermostat shows a lashing

Batteries are exhausted and

Replace with new batteries.

 

 

symbol on the LCD screen.

need replacing.

 

 

 

 

 

 

 

 

 

 

The thermostat’s LCD display

The heating is not required

The heat demand is send to the HC60NG as a value

shows a symbol but the

at this moment.

between 0-100%. The HC60NG will adjust the boiler

heating does not switch on.

 

on time to meet this requirement. That is why the

 

 

 

 

heating will be off sometimes even if the symbol is

 

 

 

 

displayed. To check if RF system is communicating

 

 

 

 

properly press the

button to increase the set

 

 

 

 

temperature a few degrees above the current

 

 

 

 

temperature. The heating should come on after a few

 

 

 

 

seconds.

 

 

 

 

 

 

 

 

The thermostat shows a lashing

Fault in thermostat

Remove and re-insert the batteries in the thermostat.

 

 

symbol on the LCD

 

If the

 

symbol does not clear itself in a few

 

 

 

 

screen.

 

minutes call the installer.

 

 

 

 

 

 

 

 

fAq’s & TRoublESHooTING

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Contents CM921 User Guide Plumbnation.co.uk Controls Layout To install the Batteries Installing the BatteriesRunning the Built-in Heating Program Setting the Date and TimeTo set the Date and Time Reviewing the Heating Program Built-in Heating ProgramModifying the Heating Program To press or buttons To enable time periods To disable time periodsDisabling / Enabling Time Periods Adjusting the Time Choosing the Operating ModeDuring 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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