Sunday, June 22, 2008

How to change the temperature scale on a Honeywell T6575 Thermostat

[The complete documentation can be found at]


This was bugging me for a while - the thermostat in my condo was configured to display in Fahrenheit.  I had removed the device figuring there would be a jumper or dipswitch on the back, but I had assumed incorrectly.  It turns out this device contains an EEPROM for storing configuration data.  Getting into the setup is relatively straight forward.


  1. Change the temperature set point to 10C or 50F.  If it will not go this low then the minimum set point has been modified - you can access setup by selecting the lowest your device will go.
  2. Wait about 3 seconds until the room temperature is displayed
  3. Press and hold the UP and DOWN buttons until tS is displayed
  4. Press  UP once to show the current setting, press UP again so that it changes to Celcius.
  5. Press DOWN to commit your change.
  6. Continue pressing DOWN as you cycle through the available options (db, OP, uC, uH, CO, CL, HL, ES, rt) until you reach rT.
  7. Press DOWN once more and the unit should return to the current room temperature display, this time in the scale of your choice!


mel said...

Thanks!! I removed the cover of the one in my condo looking for a switch too. I also want to know how to adjust to +/- 2 degree F range, so thanks for the link to the manual.

Anonymous said...

I know this sounds silly, but when I hold both buttons, it doesn't do anything.

Does anyone have any ideas?

Steven Berkovitz said...

Did you follow the directions completely? Your lowest set point might be lower than mine.

Anonymous said...

I did not follow the instructions. I have done so this time around and it works. Thanks so much for the thread!

Anonymous said...

Fantastic tip! it work flawlessly

Anonymous said...

Thank you! Mine just automatically changed itself and I couldn't find out how to reset it!

nikhil joshi said...

I have followed the instructions and change temp to Celsius flawlessly. Thank you!

Tollu said...

10 years later and this worked perfectly!

Nitin Ruhela said...

Thank you so much have been looking for this for long.