The Honeywell CM721 is a programmable room thermostat designed to control your heating system efficiently, providing comfortable temperatures when you are at home and energy savings when you are away. The following instructions explain how to program and use the thermostat to provide the most home comfort at the least cost.
This section shows you how to set up 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 room temperature is already displayed move on to Step 2 Setting the Date and Time.
To install the Batteries:
STEP 2: Setting the Date and Time
To set the Date and Time:
STEP 3: Running the Built-in Heating Program
The thermostat is now ready for operation. Press the AUTO button and the built-in heating program will start running. Note: The built-in heating program has been designed to provide normal comfort requirements, but if you want to customize the settings please see the next section ‘Programming the CM721’.
The Built-in Heating Program
The built-in heating program has 4 temperature level changes that can be set between 3.00 am and 2.50 am the following day – 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.
| Period | 1 | 2 | 3 | 4 |
| Time | 6:30 | 8:00 | 18:00 | 22:30 |
| Temperature | 21°C | 18°C | 21°C | 16°C |
Reviewing the Heating Program
To review or edit the heating program use the PROGRAM
To change the heating program
Disabling / Enabling Time Periods
The thermostat has 4 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 4 can be removed from (or returned to) the heating program profile.
To disable or enable time periods
Choosing the Operating Mode
The thermostat can operate in three different modes: Automatic, Manual or Off. To set the operating mode press either of the AUTO, MAN, or OFF buttons. The screen indicates which mode is currently active by displaying AUTO, MAN, or OFF.
SERVICE indicator
Note: This option only works if activated by your installer.
The ‘SERVICE’ indicator is displayed at set intervals as a reminder that your heating system requires a routine check. Please call your installer to arrange a maintenance visit. The ‘SERVICE’ indicator will remain on the display of the CM721 until it is either reset or disabled by your installer. The CM721 heating system will continue to operate as normal.
Automatic Summer/Winter Time Change
The CM721 has a built-in Automatic Summer/Winter Time Change feature that will automatically adjust the clock forward or backward by one hour for ‘Daylight Saving Time’. This is carried out on the last Sunday of March and October each year.
Optimum Start
Optimum Start is a program that ensures that the optimum temperature conditions are achieved at the required times. This is an Energy Efficiency feature that adjusts the start time of your heating system depending on how cold it is. For example, on cold days your heating system will be started earlier to ensure that your home is warm when you get up (at the target temperature) and on warmer days the heating system will be started later to save energy. So, if the Optimum Start Feature is used, then the time/temperature settings which are entered into the thermostat should be set to when you want to be warm by and not when you want the heating system to start.
How do I change the batteries on the thermostat when they run out?
The thermostat constantly monitors the battery power level, which typically lasts for about 2 years before needing to be replaced. When the power is running low a flashing
How do I set one temperature for the whole day?
To operate as a simple thermostat with one temperature throughout the day, select the manual operating mode by pressing the MAN button. Adjust the temperature by pressing
BDR91 Relay Box Controls Layout
The relay box will normally be found mounted close to the boiler.
What does it mean when the BDR91 relay box green LED is ON?
The green LED indicates the normal operation of the radio frequency system. When the green LED is ON the boiler is also ON. When the LED is OFF the boiler is OFF.
When do I need to use the push button?
You should use the push button to control your boiler only when the RF communication is lost (see the Troubleshooting Guide).
| Symptom | Remedy |
| Blank Display (Power Loss). | Check batteries are installed by removing the battery cover.
Check batteries have been installed in the correct orientation.
Replace the batteries. |
| Display shows flashing symbol. | The batteries in the thermostat are low on power – Replace the batteries. |
| Display shows symbol. | A fault has occurred in your heating system. Remove and re-insert the batteries.
If the |
| Display shows the word ‘SERVICE‘ | Your installer has set a scheduled maintenance alert period on your CM721 as a recommendation that your heating system should receive a routine inspection.
Call your installer to arrange a maintenance visit.
Note: The CM721 and heating system will continue to operate as normal. |
| BDR91 red LED is constantly on or flashing | RF communication lost due to the wrong location of the room unit – Hook the room unit back on the wall bracket where RF communication was reliable.
Call installer
NOTE: You can control the boiler manually when the RF communication is lost: Press the BDR91 push button to switch the boiler on and off. When the green LED is on – the boiler is on. |
The Honeywell CM727 is a programmable room thermostat designed to control your heating system efficiently, providing comfortable temperatures when you are at home and energy savings when you are away. The following instructions explain how to program and use the thermostat to provide the most home comfort at the least cost.
Controls Layout
This section shows you how to set up 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 room temperature is already displayed move on to Step 2 Setting the Date and Time.
To install the Batteries:
STEP 2: Setting the Date and Time
To set the Date and Time:
STEP 3: Running the Built-in Heating Program
The thermostat is now ready for operation. Press the AUTO button and the built-in heating program will start running.
The Built-in Heating Program
The built-in heating program has 4 temperature level changes that can be set between 3.00 am and 2.50 am the following day – 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.
Monday to Friday (Day 1 to 5)
| Period | 1 | 2 | 3 | 4 |
| Time | 6:30 | 8:00 | 18:00 | 22:30 |
| Temperature | 21°C | 18°C | 21°C | 16°C |
Saturday & Sunday (Day 6 & 7)
| Period | 1 | 2 | 3 | 4 |
| Time | 8:00 | 10:00 | 18:00 | 23:00 |
| Temperature | 21°C | 21°C | 21°C | 16°C |
Reviewing the Heating Program
To review or edit the heating program use the PROGRAM
To change the heating program
Disabling / Enabling Time Periods
The thermostat has 4 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 4 can be removed from (or returned to) the heating program profile.
To disable or enable time periods
Choosing the Operating Mode
The thermostat can operate in three different modes: Automatic, Manual or Off. To set the operating mode press either of the AUTO, MAN, or OFF buttons. The screen indicates which mode is currently active by displaying AUTO, MAN, or OFF.
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:
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 MAN or AUTO mode. To cancel the HOLIDAY function or to exit the function at any time press the button
Using the Special Features
How do I change the batteries on the thermostat when they run out?
The thermostat constantly monitors the battery power level, which typically lasts for about 2 years before needing to be replaced. When the power is running low a flashing symbol
How do I set one temperature for the whole day?
To operate as a simple thermostat with one temperature throughout the day, select the manual operating mode by pressing the MAN button. Adjust the temperature by pressing the
What does it mean when the BDR91 relay box green LED is ON?
The green LED indicates the normal operation of the radio frequency system. When the green LED is ON the boiler is also ON. When the LED is OFF the boiler is OFF.
When do I need to use the push button?
You should use the push button to control your boiler only when the RF communication is lost (see the Troubleshooting Guide).
This product and its associated documentation and packaging are protected by various intellectual property rights belonging to Honeywell Inc. and its subsidiaries and existing under the laws of the UK and other countries. These intellectual and property rights may include patent applications, registered designs, unregistered designs, registered trademarks, unregistered trademarks and copyrights. Honeywell reserves the right to modify this document, product and functionality without notice. This document replaces any previously issued instructions and is only applicable to the product(s) described. This product has been designed for applications as described within this document. For use outside of the scope as described herein, refer to Honeywell for guidance. Honeywell cannot be held responsible for the misapplication of the product(s) described within this document. Manufactured for and on behalf of the Environmental and Combustion Controls Division of Honeywell Technologies Sàrl, ACS-ECC EMEA, Z.A. La Pièce 16, 1180 Rolle, Switzerland by its Authorised Representative Honeywell Inc.
| Symptom | Remedy |
| Blank Display (Power Loss). | Check batteries are installed by removing the battery cover.
Check batteries have been installed in the correct orientation.
Replace the batteries. |
| Display shows flashing symbol | The batteries in the thermostat are low on power – Replace the batteries. |
| Display shows symbol. | A fault has occurred in your heating system. Remove and re-insert the batteries.
If the |
| Display shows the word ‘SERVICE‘ | Your installer has set a scheduled maintenance alert period on your CM727 as a recommendation that your heating system should receive a routine inspection.
Call your installer to arrange a maintenance visit.
Note: The CM727 and heating system will continue to operate as normal. |
| BDR91 red LED is constantly on or flashing | RF communication lost due to the wrong location of the room unit – Hook the room unit back on the wall bracket where RF communication was reliable.
Call installer
NOTE: You can control the boiler manually when the RF communication is lost: Press the BDR91 push button to switch the boiler on and off. When the green LED is on – the boiler is on. |
…an explanation for householders
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. So, a programmable room thermostat lets you choose what times you want the heating to be on, and what temperature it should reach while it is on. It will allow you to select different temperatures in your home at different times of the day (and days of the week) to meet your particular needs. Turning a programmable room thermostat to a higher setting will not make the room heat up any faster. How quickly the room heats up depends on the design of the heating system, for example, the size of the boiler and radiators.
Neither does the setting affect how quickly the room cools down. Turning a programmable room thermostat to a lower setting will result in the room being controlled at a lower temperature, and saves energy. The way to set and use your programmable room thermostat is to find the lowest temperature settings that you are comfortable with at the different times you have chosen, and then leave it alone to do its job. The best way to do this is to set low temperatures first, say 18°C, and then turn them up by one degree each day until you are comfortable with the temperatures. You won’t have to adjust the thermostat further. Any adjustments above these settings will waste energy and cost you more money.
If your heating system is a boiler with radiators, there will usually be only one programmable room thermostat to control the whole house. But you can have different temperatures in individual rooms by installing thermostatic radiator valves (TRVs) on individual radiators. If you don’t have TRVs, you should choose a temperature that is reasonable for the whole house. If you do have TRVs, you can choose a slightly higher setting to make sure that even the coldest room is comfortable, then prevent any overheating in other rooms by adjusting the TRVs. 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 program, for example, ‘Override’, ‘Advance’ or ‘Boost’. These are explained in the manufacturer’s instructions. Programmable room thermostats need a free flow of air to sense the temperature, so they must not be covered by curtains or blocked by furniture. Nearby electric fires, televisions, and wall or table lamps may prevent the thermostat from working properly.
Honeywell Control Systems Ltd. Arlington Business Park,
Bracknell Berkshire RG12 1EB Technical Help Desk: 08457 678999 www.honeywelluk.com 50039991-003 A © 2009 Honeywell International Inc.
Download Manual:
Honeywell Home CM721 Programmable Thermostat User Guide
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Honeywell Home CM721 Programmable Thermostat Installation Guide
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