Download Print this page

Honeywell CM921 User Manual

1 day wireless programmable room thermostat with lot technology
Hide thumbs


Honeywell Control Systems Ltd.
Arlington Business Park,
RG12 1EB
Technical Help Desk: 08457 678999
42011077-103 R1
© 2006 Honeywell International Inc.
CM921 - User Guide
1 day Wireless Programmable Room Thermostat
with LoT technology
The Honeywell CM921 is a 'wireless' programmable room thermostat designed to
control you heating system efficiently, providing comfortable temperatures when you
are at home and energy savings when you are away. With 'wireless' communication
there is no need to provide a wired connection between the thermostat and boiler.
The following instructions explain how to set up, program and operate your
Honeywell CM921 Programmable Room Thermostat.
Wireless connection to the boiler allows you to mount the Chronotherm in your
room without decor disruption
Armchair programming feature lets you program your Chronotherm while
resting comfortably in your armchair
Ergonomic User Interface features an 'OK-button' making the CM921 very
easy to use so you always stay in control.
LoT technology provides informative 'on-screen' feedback and operational
assistance to the user.
Extra Large LCD (Liquid Crystal Display) Screen with Backlight provides
added user friendliness and clearer viewing – even in the dark.
6 independent temperature levels per day lets you set any 6 temperatures you
require (from 5 to 35°C) so you can enjoy economical comfort every day
Holiday button saves energy by letting you reduce the temperature for 1 to 99
days while you are away from home, resuming normal operation on your return.
Automatic Summer/Winter Time Change will adjust the clock automatically for
'Daylight Saving Time'.
Built-in Memory holds the user program indefinitely so that it is never lost –
even if you remove the batteries.
Optimum Start option is an advanced feature which ensures that the optimum
temperature conditions are achieved at the required times (option set by your



  Related Manuals for Honeywell CM921

  Summary of Contents for Honeywell CM921

  • Page 1 Description The Honeywell CM921 is a ‘wireless’ programmable room thermostat designed to control you heating system efficiently, providing comfortable temperatures when you are at home and energy savings when you are away. With ‘wireless’ communication there is no need to provide a wired connection between the thermostat and boiler.
  • Page 2 the nation’s favourite PLUMBING & HEATING SUPPLIES FREE SHIPPING SECURE PAYMENTS on all orders over £100 to mainland UK shop online with confidence FINANCE AVAILABLE PRICE MATCH spread the cost with low interest rates always get the best deals available we have H U G E R E D U C T I O N S...
  • Page 3: Table Of Contents

    WHAT IS A PROGRAMMABLE ROOM THERMOSTAT? An explanation for householders ........17 Manufactured for and on behalf of the Environment and Combustion Controls Division of Honeywell Technologies Sàrl, Ecublens, Route du Bois 37, Switzerland by its Authorised Representative Honeywell International Inc.
  • Page 4: Step 1: Installing The Batteries

    This section shows you how to setup and run the thermostat in 3 simple steps: STEP 1: Installing the Batteries Note: Please follow the instructions in this section only if the thermostat screen is blank (no symbols or digits are displayed). If the screen displays some information move on to STEP 2: Setting the Date and Time.
  • Page 5: Step 2: Setting The Date And Time

    The built-in heating program has been designed to provide normal comfort requirements, but if you want to customise the default settings (as shown on the next page) please see the next section ‘PROGRAMMING THE CM921’.
  • Page 6: The Built-In Heating Program

    The Built-in Heating Program The built-in heating program has 6 temperature level changes that can be set between 3.00am and 2.50am - allowing you to maintain the evening temperature after midnight. Each temperature level can be set between 5°C and 35°C, and adjusted in 0.5°C increments.
  • Page 7 b. To adjust the period start time press the buttons and ‘TIME 1 OK?’ will be displayed. Holding the button down will change the time quickly. Note: If you are pressing the buttons and the display flashes the next change period, it means the next change will be pushed forward if you continue to press buttons).
  • Page 8: Disabling / Enabling Time Periods

    Disabling / Enabling Time Periods The thermostat has 6 periods that can be programmed, but you may not need all of these switch points for your heating requirements. Therefore, any period from 2 to 6 can be disabled or enabled as follows: To disable time periods: Go to the desired period ( ) by moving the slider switch to the PROG...
  • Page 9: Choosing The Operating Mode

    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. •...
  • Page 10: Temperature Override

    • Temperature Override During normal operation (AUTO mode) the programmed temperature can be adjusted manually by pressing the buttons. The ‘target‘ temperature will be displayed and lash for 5 seconds – during this time the buttons can be used to modify the set value. Note: This temperature override is cancelled at the next programmed temperature change.
  • Page 11: Changing The User Parameters

    Changing the User Parameters The user mode allows you to modify some basic settings of the thermostat to meet your personal preferences. You can change the time display format (24hr or AM/PM), reset the heating program to the built-in settings and disable or enable the summer/ winter time change feature.
  • Page 12: Change The Time Format

    c. Now choose which one of the following parameters you would like to change: i) Change the time format ‘CLOCK SELECT’ should be displayed on the screen - press the buttons to select the preferred time format (12=AM/PM format, 24=24hr format) and the display will lash, indicating a change has been made.
  • Page 13: Troubleshooting Guide

    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.
  • Page 14 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).
  • Page 15: Frequently Asked Questions

    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’...
  • Page 16 How do I remove the thermostat from the table stand or wall bracket? After programming is inished always replace the thermostat back on the wall holder or table stand. Wall bracket Table stand HC60NG Relay Box Controls Layout Push button and relay status LED’s What does it mean when the HC60NG relay box green LED is ON? Green LED indicates normal operation of the radio frequency system.
  • Page 17 Can I use my CM921 to control my air-conditioning system? Yes, if your system has been set up correctly you can use your thermostat to control the cooling. To switch the thermostat between heating and cooling modes press buttons together for 5 seconds in any of the product operating modes (AUTO, MAN or OFF).
  • Page 18: An Explanation For Householders explanation for householders (The following explanation applies to heating applications only) A programmable room thermostat is both a programmer and a room thermostat. A programmer allows you to set ‘On’ and ‘Off’ time periods to suit your own lifestyle. A room thermostat works by sensing the air temperature, switching on the heating when the air temperature falls below the thermostat setting, and switching it off once this set temperature has been reached.
  • Page 19 The time on the programmer must be correct. Some types have to be adjusted in spring and autumn at the changes between Greenwich Mean Time and British Summer Time. You may be able to temporarily adjust the heating programme, for example, ‘Override’, ‘Advance’...