Honeywell CM721 manual FAQ’s, How do I change the batteries on the thermostat when they run out?

‘Using the Features’ OPERATING THE CM721

•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 which 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 upon 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.

FAQ’s

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 replaced. When the power

is running low a flashing symbol will be displayed on the screen. To change the batteries follow the steps in the above section (‘STEP 1: Installing the Batteries’ on page 3), replacing the used batteries with new ones in Step c. Note: While changing the batteries your program settings will be stored but you may need to adjust the time settings to be correct.

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 or buttons - this can be set anywhere from 5°C to 35°C in 0.5°C steps. The thermostat will continue to maintain this temperature until another operating mode is selected or the temperature is adjusted.

BDR91 Relay Box Controls Layout

The relay box will normally be found mounted close to the boiler.

Push button and relay status LED’s

What does it mean when the BDR91 relay box green LED is ON?

The green LED indicates 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).

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