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.
FAQ’s
BDR91 Relay Box Controls Layout
The relay box will normally be found mounted close to the boiler.
Push button and relay status LED’s
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.
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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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 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,
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