Honeywell CM921 User manual

Honeywell Control Systems Ltd.
Arlington Business Park,
Bracknell
Berkshire
RG12 1EB
Technical Help Desk: 08457 678999
www.honeywelluk.com
CM921 - User Guide
1 day Wireless Programmable Room Thermostat
with LoT technology
42011077-103 R1
© 2006 Honeywell International Inc.
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/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
installer).

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Contents
GETTING STARTED WITH THE CM921
STEP 1: Installing the Batteries......................................... 3
STEP 2: Setting the Date and Time................................... 4
STEP 3: Running the Built-In Heating Program ................ 4
PROGRAMMING THE CM921
The Built-in Heating Program............................................ 5
Reviewing the Heating Program ....................................... 5
Modifying the Heating Program........................................ 5
Disabling / Enabling Time Periods ................................... 7
OPERATING THE CM921
Choosing the Operating Mode ......................................... 8
AUTO mode............................................................. 8
MAN mode .............................................................. 8
OFF mode................................................................ 8
Adjusting the Time............................................................ 8
During Normal Operation.................................................. 8
Temperature Enquiry ............................................... 8
Temperature Override ............................................. 9
Using the Special Functions ............................................. 9
HOLIDAY Function .................................................. 9
FINE TUNING THE CM921
Changing the User Parameters ...................................... 10
Change the Time Format....................................... 11
Reset the Built-in Program..................................... 11
Summer / Winter Time Change ............................. 11
FAQ’s & TROUBLESHOOTING
Trouble Shooting Guide .................................................. 12
Frequently Asked Questions........................................... 14
WHAT IS A PROGRAMMABLE ROOM THERMOSTAT?
An explanation for householders .................................... 17
Controls Layout
Day / Date Display
Time Display
LoT technology Display
Heating On Indicator
Battery Low Indicator
Temperature Display
Temperature Change Buttons
Temperature Enquiry Button
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Slider Switch
Green OK Button
Program Buttons
Battery Compartment Lid
Battery Compartment
Holiday Function Button
Time Change Buttons
1..6
AUTOMANOFF
CM921
DATE
PROG
AUTO
MAN
OFF
14
15
1 2 3 54 6
8
9
10
7
13 12 11
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.

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.
To install the Batteries:
a. Lift up the front cover of the thermostat
to reveal the battery cover and product
controls.
b. Remove the battery cover by pressing
down and sliding out.
c. Insert the 2 x AA LR6 Alkaline Batteries
supplied with the thermostat, ensuring
the correct orientation (see ‘Controls
Layout’ on page 2).
d. After a short pause the thermostat will
display information on the screen and
is now ready for use.
e. Replace the battery cover by sliding
it firmly back into the front of the
thermostat. PLEASE RESPECT YOUR ENVIRONMENT!
Take care to dispose of used batteries carefully.

STEP 2: Setting the Date and Time
To set the Date and Time:
a. Move the slider switch to the DATE position. ‘SET THE DAY’ will be displayed on
the screen and the day digits will be flashing.
b. Use the or buttons to set the correct day. When either of these buttons
are pressed ‘DAY OK?’ will be displayed. Once the correct day is reached, press
the green button to confirm.
c. Now the month digits will start flashing and ‘SET THE MONTH’ will be displayed.
Change the month and then the year using the or buttons, pressing the
green button to save any changes made. (If an invalid date has been entered
you will be returned to the start of the date setting mode).
d. After setting a valid date, the time digits will begin flashing and ‘SET THE TIME’
will be displayed.
e. Use the or buttons to set the correct time. Each press of the button will
change the time by one minute and holding the button down will change the time
slowly at first and get progressively quicker. Once the correct time is set, press
the green button to confirm then ‘CHANGES SAVED’ will be displayed for a
moment followed by ‘DATE COMPLETE’.
Note: If the slider switch is moved at any time before ‘DATE COMPLETE’ is displayed
the changes to the date and time will NOT be saved.
STEP 3: Running the Built-in Heating Program
The thermostat is now ready for operation. Move the slider switch to the AUTO
position and the built-in heating program will start running. 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’.

DATEPROGAUTOMANOFF

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. The factory default program for heating is as follows:
Reviewing the Heating Program
To review or edit the heating program move the slider switch to the PROG position
then use the or buttons to navigate between the 6 individual programming
periods.
Modifying the Heating Program
To change the heating program:
a. Set the slider switch to the PROG position, entering programming mode. ‘SET
TIME 1’ will be displayed and the time settings for period 1will be flashing. The
active period is highlighted by a flashing square symbol around the numbers at
the bottom of the screen.
Period 1 2 3 4 5 6
Time 6:30 8:00 12:00 14:00 18:00 22:30
Temperature 21°C 18°C 21°C 18°C 21°C 16°C
DATEPROGAUTOMANOFF
165432

b. To adjust the period start time press the or buttons and ‘TIME 1 OK?’ will
be displayed. Holding the button down will change the time quickly.
Note: If you are pressing the or buttons and the display flashes the next
change period, it means the next change will be pushed forward if you continue
to press or buttons).
c. Press the green button to confirm the setting. ‘CHANGES SAVED’ is displayed
for 1.5 seconds then ‘SET TEMP 1’ will be shown.
Note: If the original time setting did not require adjustment press the green
button to move on to step ‘d.’.
d. The temperature setting for period 1will now be flashing. To adjust this press the
or buttons and ‘TEMP 1 OK?’ will be displayed.
e. Press the green button to confirm the setting. ‘CHANGES SAVED’ will be
displayed for a moment followed by ‘SET TIME 2’.
f. The next time and temperature period will now be active. Adjust this by repeating
steps b - e above until all 6 periods are set or move the slider switch to the AUTO
position to run the program as set, at any time.
g. After setting period 6‘CHANGES SAVED’ will be displayed as before.
i. To exit the programming mode move the slider switch to the desired operating
mode - AUTO, MAN or OFF. Note: To run the adjusted program select the AUTO
mode.
Note: If the unit is left in programming mode for more than 10 minutes without
the slider being moved or any buttons pressed, ‘MOVE THE SLIDER’ will be
displayed. Press a button to finish programming the thermostat or move the
slider to select the desired operating mode.

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 ( 2to 6) by moving the slider switch to the PROG
position, then using the and buttons to navigate, ensuring the correct
period is highlighted with the flashing square symbol. Press and hold the
button for at least 2 seconds and the display will indicate the period has been
removed from the program.
To enable time periods:
Navigate to the disabled period by moving the slider switch to the PROG
position, then using the and buttons. Once selected ‘DISABLED’ will be
displayed. Press and hold the button for at least 2 seconds and ‘ENABLED’ will
be displayed for a moment before returning to normal programming 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.
• AUTO (automatic) mode
Automatic mode sets the thermostat to follow the temperature program (default
or personalised). Operating the thermostat in this mode is the best way to
maintain a high level of temperature comfort whilst maximising your energy
savings.
• MAN (manual) mode
Manual mode sets the thermostat to act as a simple thermostat with a fixed
setpoint throughout the day. The setpoint can be adjusted from 5°C to 35°C
by using the or buttons. The thermostat will continue to maintain this
temperature until another operating mode or temperature is selected.
• OFF mode
Off mode sets the thermostat to control to a minimum temperature setting of 5°C
(default) that acts as a frost protection measure for your home. This value can be
adjusted by calling your installer.
Adjusting the Time
To adjust only the time during normal operation use the or buttons to adjust
the time and press the green button again to confirm any changes.
During Normal Operation
• Temperature Enquiry
In AUTO and MAN operating modes the thermostat will display the current room
temperature, which is indicated by the text ‘ROOM TEMP’ displayed on the
screen. To review the programmed ‘target’ temperature (the temperature which
the thermostat is trying to maintain) press the button. This ‘target’ temperature
value will be displayed flashing and the text ‘TARGET TEMP’ will be shown for 5
seconds before returning to the current room temperature value.
In OFF operating mode the thermostat again displays the current room
temperature, as above, but when the button is pressed the text ‘FROST TEMP’
is displayed indicating the set value to protect your home. To modify this value
please contact your installer.

• Temperature Override
During normal operation (AUTO mode) the programmed temperature can be
adjusted manually by pressing the or buttons. The ‘target‘ temperature
will be displayed and flash for 5 seconds – during this time the or buttons
can be used to modify the set value.
Note: This temperature override is cancelled at the next programmed
temperature change.
Using the Special Functions
• HOLIDAY Function
The holiday function allows you to set a constant temperature (default = 10°C)
for a specified number of days (from 1 - 99 days). This lets you save energy and
related costs when you are away from home, but resumes normal operation on
the day of your return.
To set the Holiday function:
a. Move the slider switch to the AUTO or MAN position.
b. Press the button to display the holiday days counter and temperature
setting, along with the holiday indicator .
c.
The day after the current day will be selected and ‘RETURN DATE OK?’ will be
displayed. Press the or time buttons to set the holiday time (1 – 99 days).
Note: (The day and date will update according to the number of days
selected).
d. Press the green button to confirm the setting.
e. ‘CHANGES SAVED’ will be displayed for a moment followed by ‘TEMP OK?’.
Press the or buttons to set the holiday temperature (5°C - 35°C)
f. Press the green button to confirm the setting. ‘HOLIDAY MODE’ will now
be displayed on the screen until the return date is reached or the holiday
mode is cancelled.
The thermostat will now control to the new temperature for the set number of days
that your home is vacant. At midnight the holiday counter will be reduced by one until
the selected number of days have passed. The thermostat will then return to normal
operation as set by the slider switch position (AUTO or MAN position). To cancel the
HOLIDAY setting or to exit the function at any time press the button a second time
or move the slider switch to a different position.