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Honeywell L7224U low limit bypass

jpotter04210 Member Posts: 1
edited January 2021 in THE MAIN WALL
Does anyone know how to bypass the low limit on a Honeywell L7224U?
I just had to replace the control assembly on my boiler as it was faulty. The old assembly was analog and so i installed a timer to bypass the low limit switch during the day and night when no hot water usage was anticipated. It has worked very well for 15 years or so. I can't see how to bypass it on the new digital model.


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    I think you're out of luck. But maybe, you can add another temperature sensor and wire your timer to ZR. If I had a few moments I could put my brain to it.
    But I bet @EdTheHeaterMan could figure it out, with diagrams ;)
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,600
    edited January 2021
    @jpotter04210 Press and Hold the 3 buttons < > I Up, Down, and Information This will put you into program or setup mode.

    Once you see the display change to HL then you are in the program mode
    Now press the I button to toggle thru the program menu 2 times. the display will say LL that stands for low limit
    now press the down arrow to lower the temperature to the lowest setting. On OEM controls that may be 120°
    on the L7224U the lowest setting is OFF
    That should do it but you cant connect a timer to it to bring it back on.

    If you need to maintain temperature for DHW on a timer you will need to get the old analog control and set it up with the timer like you did on the original control The contacts in the digital control for low limit don't have wires that you can disconnect to insert a set of timer contacts.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,600
    There may be a way to do the timer using the ZR and the controls programming BUt you will need a second aquastat to measure the boiler temperature at the Low Limit Setting. You will need an L4006A aquastat and a place to install it in the boiler using a Well Adaptor. Is there an extra tapping in the boiler near the top where you can do that?
    @jpotter04210 If yes then I can go over the details if you are interested
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics