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Buderus GB 142 - 2F

Seems every time it gets cold, we get an error code! And the heat isn't really the issue for us. The lack of hot water tends to make people cranky.....

So getting a 2F code. I saw a video indicating that the resistance on the 3 sensors (safety, supply and return), should all be within 10% of each other, since they should all be reading the same temperature. Can someone confirm if that's correct?
On mine, I got readings of 4700 and 4800 ohms on the safety and supply sensors, but 6000 ohms on the return sensor, which suggests its gone bad. I don't have my temp gun here (its out of town for a few days), but I did use a digital food thermometer and got similar temp readings at each sensor location...

Agree? Bad sensor?

Comments

  • mikeapolis mikeapolis Member Posts: 16
    Bosch has excellent tech support. If you haven't already contacted them, I'd recommend giving them a call:
    Tel: (603)-552-1100 Toll Free: 1-800-BUDERUS

    Here's a link to the manual(Page 49 for your 2F Code):
    https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Buderus - GB142-30 - Service Manual.pdf

    Page 91 shows how to replace those sensors
  • Big Ed_4Big Ed_4 Member Posts: 1,433
    If the boiler is off on error the temperature should be the same . You can just feel the locations to see if they are close . I would replace all three sensors , the good ones keep as spares ..
    I have enough experience to know , that I dont know it all
  • kinderhundkinderhund Member Posts: 12
    Update - replaced the sensor, now getting similar resistance across all 3 sensors. Still getting 2F error though, which according to the manual now indicates primary circulation pump. Going to see if I can hear it spin up on startup. Any other way to know if it's operating?
  • IronmanIronman Member Posts: 5,801
    Is there any temperature difference between supply and return?

    It could also be air bound.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • mikeapolis mikeapolis Member Posts: 16
    What kind of circulator is it? If it's not an ecm circulator, you can use a Grundfos Run Indicator Magnetic Rotation Key. I agree with Ironman that it could be air bound.
    Ironman
  • IronmanIronman Member Posts: 5,801
    edited October 16
    It’s usually a Grundfos 15-42 or 15-58.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • Big Ed_4Big Ed_4 Member Posts: 1,433
    edited October 18
    Top left on heat exchanger is where the float vent is installed to remove air. Its easy to replace... Just make sure you hang the float like the one you pull out ..
    I have enough experience to know , that I dont know it all
  • kinderhundkinderhund Member Posts: 12
    Update: I did my best to remove air. Still nothing. Called in a tech to have a look, and they got Buderus on the phone as well. Did a proper flush of the system, refilled and purged. Still getting 2F code.
    According to Buderus, the issue is actually the control board - there's some kind of short between the unit calling for heat for hot water, and firing the boiler. Because it prioritizes hot water, it won't fire for floor heating either. By setting the water temp to zero, we can at least heat the floor while I source a new control board.
  • mikeapolis mikeapolis Member Posts: 16
    Good luck. Hopefully, that board will take care of the issue.
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