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).

Honeywell CM921 Specifications

General

Type	Programmable Thermostat
Display	LCD
Programming	7-day programmable
Power Source	2 x AA batteries
Temperature Range	5°C to 35°C
Mounting	Wall-mounted
Voltage	230V
Frequency	50 Hz
Accuracy	±0.5°C
Control Mode	Heating
Backup	Battery backup

Summary

Description

Key Features

Controls Layout Overview

Getting Started with CM921

Installing Batteries

Instructions for installing AA LR6 alkaline batteries into the thermostat for initial setup.

Setting Date and Time

Guide to setting the current date and time on the CM921 thermostat.

Running Built-In Heating Program

Procedure for starting the pre-programmed heating schedule on the CM921.

Programming the CM921

Built-in Heating Program Details

Details of the factory default heating program with 6 temperature level changes and timings.

Reviewing Heating Program

How to view or edit the existing heating program schedule on the CM921.

Modifying Heating Program

Step-by-step guide to changing the time and temperature settings for each period.

Disable or Enable Time Periods

Instructions on how to disable or enable specific time periods (2-6) in the heating program.

Operating the CM921

Choosing Operating Mode

Guide to selecting between AUTO, MAN (manual), and OFF operating modes.

Adjusting Time During Operation

How to adjust the thermostat's time during normal operation.

Temperature Enquiry

How to check current room temperature and target temperature settings.

Manual Temperature Override

How to temporarily adjust the target temperature manually in AUTO mode.

Holiday Function Setup

Instructions for setting a constant temperature for a specified number of days when away.

Fine Tuning CM921 Settings

Customizing User Parameters

Guide to modifying basic thermostat settings like time format and program reset.

Advanced Parameter Adjustments

Adjusting time format, resetting the program, and managing summer/winter time change.

FAQs and Troubleshooting

Removing Thermostat from Mount

Instructions on how to detach the thermostat from its wall bracket or table stand.

Understanding HC60NG Relay Box LEDs

Explanation of the HC60NG relay box green LED status and its meaning for system operation.

Air-Conditioning Control Capability

Information on using the CM921 thermostat to control air-conditioning systems.

Checking Thermostat Operation

Guidance on checking the thermostat's functionality if the heating system experiences issues.

Understanding Programmable Thermostats