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Honeywell CM921 Wireless Programmable Room Thermostat User Guide

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.  
The following instructions explain how to set up, program and operate your  
Honeywell CM921 Programmable Room Thermostat.  
Features  
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/WinterTime 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  
installer).  
Honeywell Control Systems Ltd.  
Arlington Business Park,  
Bracknell  
CM921 - User Guide  
1 day Wireless Programmable Room Thermostat  
with LoT technology  
Berkshire  
RG12 1EB  
Technical Help Desk: 08457 678999  
42011077-103 R1  
© 2006 Honeywell International Inc.  
firealarmresources.com  
GeneralDetails
NameHoneywell CM921 Wireless Programmable Room Thermostat User Guide
MakeHoneywell
LanguageEnglish
FiletypePDF (Download)
File size0.31 MB
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Honeywell CM921 Wireless Programmable Room Thermostat User Guide
Get the free PDF manual for the Honeywell CM921 Wireless Programmable Room Thermostat User Guide and access setup steps, usage instructions, and troubleshooting tips. 👉 View online or download now to keep your thermostat running smoothly!

Honeywell CM921 Manual: Questions and Answers

Can the Honeywell CM921 control both heating and cooling systems?

The CM921 is designed to control heating systems only. User Guide, p. 1

What do the display messages mean on the Honeywell CM921?

DisplayMeaning
AUTOAutomatic mode active, following temperature program
MANManual mode active, fixed setpoint throughout day
OFFOff mode active, frost protection at 5°C default
ROOM TEMPCurrent room temperature shown
TARGET TEMPProgrammed temperature the thermostat maintains
FROST TEMPFrost protection setpoint in OFF mode

User Guide, p. 9

What does the HOLIDAY MODE indicator mean on the Honeywell CM921?

The thermostat is controlling to a constant temperature you set for a specified number of days while away, then returns to normal operation on your return date. User Guide, p. 10

How do I reset the heating program to factory settings?

Move the slider switch to OFF, then press and hold the button for approximately 5 seconds to enter user mode.

  1. Press the time button once; 'RESET PROGRAM' will display.
  2. Press the or buttons to select: 0 for user program, 1 for factory program.
  3. Press the green button to confirm.
  4. Move the slider switch to AUTO, MAN or OFF to exit user mode. User Guide, p. 12

Why is my Honeywell CM921 showing the heating symbol but heat won't turn on?

The heating may not be required at that moment; the HC60NG adjusts boiler on time to meet the heat demand percentage.

  • Heat demand is sent to HC60NG as a value between 0-100%.
  • Heating will be off sometimes even with the symbol displayed.
  • To verify RF communication, press the button to raise set temperature a few degrees above current temperature; heating should start within seconds. User Guide, p. 13

What temperature range does the Honeywell CM921 support?

5°C to 35°C, adjustable in 0.5°C increments. User Guide, p. 6

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