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How to adjust a honeywell L8148A aquastat

Mark_30 Member Posts: 4
I have a honeywell L8148A high/low aquastat. I want to set it to turn on at 160 and turn off at 180. How would I do this? I'm not sure if the round dial is the high limit or if the clip on the dial is.


  • Billy_4
    Billy_4 Member Posts: 18

    The L8148A does not have a low limit. All it has is a hi-limit and a differential to limit low temperatures on a call for heat. If you want a control with high and low limit settings you will need a L8124A or a L7124U.
  • Firedragon_4
    Firedragon_4 Member Posts: 1,436
    That's a fixed high limit control, leave it alone!

  • Mark_30
    Mark_30 Member Posts: 4

    Right now the boiler turns on at 170 and goes off at 190. I would like to have it shut down at 180 turn on at 160. Can I do it with this type of aquastat. I't doesn't matter which way I turn the dial or the dial clip, it still fires up at 170 and still goes off at 190. I want to set the dial and the dial clip at where they were before, but I can't remember what they were set at. Can anybody get me back to the same settings it was at when it was installed,and how would I do that?
  • BillW@honeywell
    BillW@honeywell Member Posts: 1,099
    This is a safety high limit control...

    unless you are a trained heating technician, DO NOT adjust the control yourself. You can cause an unsafe condition resulting in serious injury, severe property damage or worse. Use the "Find a Professional" feature on this site or contact a local pro. Safety-related controls are not a DIY project!
  • Mark_30
    Mark_30 Member Posts: 4

    I installed the boiler myself about 8 years ago. This year I installed a add-on wood/coal H/W boiler to this system. Running low on coal and I'd like to run the gas boiler a few days with this warmer weather. I moved the diff. clip on the dail to try to get a diffrent temp. setting. My coal boiler doesn't stay at 180 all the time and I didn't want the main boiler to keep starting up. What I tried to do wouldn't work so I shut down the gas boiler, left the power to my ZV's on, and used the coal boiler as my main source of heat. The dial in the aquastat is set in front of the arrow at 180, all I need to do is get the diff. right. No matter where I move the diff. clip, it still turns on at 170, and off at 190. I can set the aquastat myself, I just can't remember what it was set at in the fall before I moved it. All I'm asking is, should I set the high limit to 180 and move the diff. clip to 170?, this would give me a 10* diff. Not sure if the settings are off, or the aquastat is bad.
  • Mark_30
    Mark_30 Member Posts: 4

    Thanks anyway guy's,I got it figured out. Shuts off at 180, fires up at 160, just where I want it. Just had to think about it awhile, then it came to me.
  • DIY Homeowner
    DIY Homeowner Member Posts: 48
    DIY Rocks !!

This discussion has been closed.