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100-270 Degree high limit aquastat (manual reset) keeps

ElderGreen Member Posts: 25
opening the circuit. It is set at 210 degrees. I understand that even after the unit is done firing that it is still heating and therefore the temp can still increase. But the manual reset part means that the heat won't come back on until it is manually pushed. Can I just change this out with an automatic reset one?


  • Zman
    Zman Member Posts: 7,542
    Post Purge

    What type of boiler?

    What is the operating temp?

    This problem can normally be solved by installing a post purge relay on the boiler circulator. This helps dissipate the extra heat after the cycle.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ElderGreen
    ElderGreen Member Posts: 25
    Tyoe is a clean burn

    350 waste oil boiler. Operating temp about 180. But it is now getting to spring with the outside temps rising. The relay sounds like a good bet. Maybe i'll do both.
  • bill nye_3
    bill nye_3 Member Posts: 307

    A manual reset high limit should not be used as an operating control. You should have another aquastat set at a lower temperature as the operating control. It has to be manual reset to get some one there to realize there is a problem and take some kind of action.

    If you have a closed system with proper expansion tank and a pressure relief I would turn the(reset) high limit setting up a few degrees and then try to find out why the operating control is overshooting the set point.
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