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Please help me use this old Stadler thermostat

I am renting a home with old Stadler thermostats, which I cannot comprehend.  The units have a dial with no numbers, only sweeps to blue and red, and the switch has a crescent moon, a sun and a clock.  In the cover, it reads "TYPE 177225 6125" "AC24 V 2(2)A".  I need some operating instructions.  


  • Jamie Hall
    Jamie Hall Member Posts: 23,436
    I wish the pictures were sharper... that is a very simple bimetal thermostat. The cams inside the knob can be moved, and it appears that they can be set from inside the knob so that the index on the outside corresponds to a particular temperature and, possibly swing. Turning the knob index towards red will turn the heat on; turning it the other way will lower the set temperature. Beyond that I can't see the circuit diagram clearly enough to figure out what it does -- but I can assure you it's pretty simple.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Jolly Bodger
    Jolly Bodger Member Posts: 209
    Clock = night setback timer
    Sun = day or normal operation
    Moon= night setback

    There is not a wire on the 5 (clock) terminal. So the switch will operate the same in the Sun and Clock position. The Moon position will lower the temperature because it turn on a heater in the thermostat. This would fool the thermostat into seeing the room warmer than it is. Thus not bringing on the heat. there is no way to tell how far this would setback.

    If it had numbers it is unlikely that they would be accurate any more. Leave the switch in Sun. turn it up if you are cold and down if you are hot. If you want to do night setback put a piece of tape on the face and make day/night marks.
  • DrYattz
    DrYattz Member Posts: 2
    Thanks, everybody!
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,092
    That is the way a thermostat should be labeled... NO NUMBERS!

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    HVACNUT Member Posts: 5,863
    edited November 2019
    You're best option is to throw it in the trash heap and install a digital thermostat, Doc.
    We don't use leaches anymore either.
  • HomerJSmith
    HomerJSmith Member Posts: 2,468
    edited November 2019
    Stadler was bought out by Viega in the '90's'. This particular thermostat was used by Viessmann with their Tri-matic boiler (Atola) control. I have a bunch of them on the shelf. I never throw anything away, perhaps, I should rethink that. Do you think they'll make a come back?
    Viega has a lot of legacy information on their web site.
    If you want more heat move the dial clockwise, if you want less heat move the dial counter-clockwise. Keep the switch in the sun position and forget the night setback. Since there isn't any temp reading, use the shiver method of determining the temperature in the house. If the misses is shivering turn the dial clockwise until she stop shaking.
    Replace it with a digital thermostat. What kind of boiler do have?
  • JeffM
    JeffM Member Posts: 182
    If you want the actual instruction sheet on that thermostat, call Viega tech support they have an archive of the old stuff. There were a couple of similar looking stats from that time period, so send them your photos to assist.
  • ratanshah
    ratanshah Member Posts: 1
    I have exactly the same thermostat. Mine is labeled " Wirsbo" otherwise the same ( 30 + years old ). works well but no real programming . I one had a sheet on the thermostat as it can take floor temperature sensor.
    There must be a model number on the thermostat.