Why is the red LED on my Honeywell Thermostat relay box illuminated?
The red LED on the relay box illuminates because it's not receiving radio frequency (RF) signals from the room thermostat. This could be due to the thermostat being in a location where the RF signal is blocked, or because the thermostat batteries are dead. Try relocating the room thermostat as per the installation instructions or replace the batteries in the room thermostat.
What to do if my Honeywell Thermostat relay box doesn't react to setpoint changes?
If the relay box isn't responding to setpoint changes from the room thermostat, it's likely that the thermostat and relay box aren't properly connected. You should reset the relay box by holding the push button for 15 seconds. Then, follow the binding procedure as described in section 5) Additional Installation Information.
What to do if the red LED is on and the green one is flashing after binding Honeywell Thermostat?
If, after binding, the red LED is on and the green one flashes every 3 seconds on the relay box, it indicates an incorrect or incomplete binding procedure, or the thermostat was incorrectly positioned during binding. Repeat the binding procedure, ensuring the room thermostat is approximately 1 meter away from the relay box.
How to make the Honeywell CM721 Thermostat relay switch on if it only displays the symbol?
When the room thermostat displays the symbol, it's normal for the relay not to immediately switch on. To activate it, adjust the temperature setpoint by a few degrees using the button. The relay box should then switch on after a short delay.
What to do if the Honeywell Thermostat relay box does not react to setpoint changes?
If the relay box isn't responding to setpoint changes on the room thermostat, it's likely that the room thermostat and relay box aren't properly bound. Reset the relay box by pressing and holding the push button for 15 seconds, then follow the binding procedure as described in section 5) Additional Installation Information.
What to do if the Honeywell CM721 Thermostat relay box red LED is on and the green one is flashing after binding?
If, after binding, the red LED is on and the green one is flashing once every 3 seconds on the relay box, it indicates an incorrect or incomplete binding procedure, or an incorrect thermostat position during binding. Repeat the binding procedure, keeping approximately 1 meter distance between the relay box and the room thermostat.
How to fix a Honeywell CM721 when the symbol is displayed but the relay doesn't switch on?
If the room thermostat displays the symbol but the relay box relay doesn't switch on, try changing the temperature setpoint by a few degrees using the button. The relay box should switch the relay on after a few seconds delay. Also, this can be normal operation. The relay box cycles the relay on and off for times proportional to the demand signal (0-100%) from the room thermostat. The symbol only indicates that the demand value is greater than 0%.
General| Type | Programmable Thermostat |
|---|---|
| Display | LCD |
| Setpoint Range | 5°C to 32°C |
| Switching Voltage | 24V AC |
| Temperature Range | 0°C to 50°C |
| Hold Feature | Yes |
| Power Source | 24V AC (Battery Backup) |
| Dimensions | 88 mm x 132 mm x 26 mm |
Details the Honeywell CM721 as a programmable room thermostat for efficient heating control.
Lists key features of the CM721 thermostat, including LCD screen and temperature levels.
Diagram and labels for the CM721 thermostat's physical controls and display elements.
Step-by-step instructions for installing batteries in the CM721 thermostat.
Procedure for setting the current date and time on the CM721 thermostat.
Instructions to start the CM721's default heating program.
Details the factory default heating program for the CM721 with time and temperature settings.
Guide on how to review and change the programmed heating times and temperatures.
Instructions for removing or re-adding programmed time periods on the CM721.
Explains the Automatic, Manual, and Off modes for operating the CM721 thermostat.
How to check target temperature and manually override settings during normal operation.
Procedure for adjusting the time on the CM721 during normal operation.
Explanation of the SERVICE indicator and when to call an installer.
Details the automatic adjustment for Daylight Saving Time on the CM721.
Explains the Optimum Start feature for efficient heating system activation.
Answers common questions about battery replacement and time adjustments.
Information regarding the BDR91 relay box and its LED indicators.
Troubleshooting steps for blank displays and low battery indicators.
Resolving issues related to the SERVICE indicator and BDR91 red LED.
Details the Honeywell CM727 as a programmable room thermostat for efficient heating control.
Lists key features of the CM727 thermostat, including 7-day programming and holiday function.
Diagram and labels for the CM727 thermostat's physical controls and display elements.
Step-by-step instructions for installing batteries in the CM727 thermostat.
Procedure for setting the current date and time on the CM727 thermostat.
Instructions to start the CM727's default heating program.
Details the factory default heating programs for weekdays and weekends for CM727.
Guide on how to review and change programmed heating times and temperatures for CM727.
Instructions for removing or re-adding programmed time periods on the CM727.
Explains the Automatic, Manual, and Off modes for operating the CM727 thermostat.
How to check target temperature and manually override settings during normal operation.
Procedure for adjusting the time on the CM727 during normal operation.
Details the holiday function for setting a constant temperature when away.
Explanation of the SERVICE indicator and when to call an installer.
Details the automatic adjustment for Daylight Saving Time on the CM727.
Explains the Optimum Start feature for efficient heating system activation.
Answers common questions about battery replacement and time adjustments.
Instructions on setting a single temperature for the entire day.
Information regarding the BDR91 relay box and its LED indicators.
Troubleshooting steps for blank displays and low battery indicators.
Resolving issues related to the SERVICE indicator and BDR91 red LED.
A general explanation of what a programmable room thermostat is and how it works.
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