Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Anticipator setting for my steam boiler

Took these images from the front of my boiler. Not sure if the images help. I don't have equipment to check the Amp draw. I read that for steam boilers, the anticipator should always be set to 1.2 (see image attached). My bills seem unusually high and I want to make sure it's running in the most efficient manner. Using old round thermostat. Thanks


  • 109A_5
    109A_5 Member Posts: 1,335
    Hello @abcaldwell,
    Back many decades ago when steam heat was going from Coal to Natural Gas the Gas Valve drew a lot more current which would burn up the heat anticipator in a T87 Thermostat. So the recommendation was 1.2 which effectively disabled the anticipator resistor. I would set it for the current draw of your actual Gas Valve 0.23 Amps.

    However if you have other control equipment between the Thermostat and the Gas Valve the actual current through the Thermostat really should be measured to be correct and accurate and not cause damage to the anticipator resistor.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • bburd
    bburd Member Posts: 869
    edited December 2023
    Setting the anticipator by the current draw of the control system does not account for the difference in lag time in various methods of heating.

    For steam heat with cast iron radiators you want a relatively long cycle. It needs to be long enough so that steam reaches all rooms before the burner shuts down. You may have to experiment a bit, but a higher amp draw setting giving less anticipation is probably what you need.

  • Jamie Hall
    Jamie Hall Member Posts: 22,881
    And furthermore... that's a starting point, not some regulation. If you are getting serious overshoot or undershoot, play with the setting a bit at a time.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ethicalpaul
    ethicalpaul Member Posts: 5,575
    But don't worry too much about "inefficiency". The BTUs are going into your house regardless.
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • abcaldwell
    abcaldwell Member Posts: 2
    Thank you for the responses.  I appreciate it.
  • Intplm.
    Intplm. Member Posts: 1,788
    One other note.
    If you have an older Honeywell T87 thermostat which I believe you do.
    You can get new thermostats that have choices for your heating system that you can select from, heat anticipators, showing in the directions.
    There's a Honeywell 87 series that has this choice. I'm sure there are others.

    Years ago it was ten wraps around an Amprobe with t-stat wire and doing the math.