How to set the heat anticipator in the mechanical thermostat for furnaces.

This is a demonstration of how the heat anticipator is set to match the amperage draw of the furnace control circuit. Several different thermostat types are shown.
This video is part of the heating and cooling series of training videos made to accompany my websites: and to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits.

24 Replies to “How to set the heat anticipator in the mechanical thermostat for furnaces.”

  1. Thanks for this, I was able to successfully replace my overly complex digital thermostat with a vintage honeywell t87 that I actually can get to do what I want.

  2. You the man! Reading this while studying for exam and couldn’t understand how. But my brain said check with Gray and bam you hit it on the money.

  3. What is the normal operation? Is it Burner/Flame come, then the blower turn on the same time or
    the Burner/Flame come on for 30 second then flame turned off, then the blower turn on next?
    I have problem that the Blower turn on too late and it is blowing kind of "warm" air and not hot air.
    (flame come out then after 1-2 minute the blower turn on).

    What is the average number (ie 0.34) for an old 1995 Carrier Furnace. Thanks.

  4. Hi gray, like all your tech vids.
    Can you clarify the correct setting of the anticipatory lever, on a white Roger's mech stat.
    I have watched your vid numerous times and it's very vague ant not clear.
    Now do you set the arrow end to required number


  5. Hello sir,keep watching your video i really appreciate the way you explained i undertand every single word.thank you so much for your time and effort to help every body to give some ideas how to do it without hiring a hoping if you have extra time to make a video about house hold boiler trouble shooting.again thanks a lot and may god bless you always.

  6. Can you please, simply tell me the proper anticipator settings for my Honeywell Class 2 LR95329? The furnace is constantly clicking/cycling, but the house stays fairly warm.

  7. Hi there! What is the typical amp draw for radiant in floor heating in a condo pls? The building's about 25 yrs old. Need to set/adjust 2 thermostats anticipator settings but not sure to what number. Cheers!

  8. Could I use sculpting clay to help seal a small leak at the fitting on my pilot tube instead of pipe dope? Not the pilot flame end but the other side thats cooler. I think the stubborn residue alone from the clay would pinch into the uneven gaps to seal it off. Thoughts?

  9. My thermostat is internal. Inside the combination gas valve. The copper wire jogs 45º to the left rounding a peg as it turns 45º to the right. From here it begins coiling about 2 1/2 times toward its center connected to an aluminum disc with ripple rings shaping it out to the edge. It is about the size of nickel. Below that sets another round disc part with ripples( not like an accordion but allows for movement up and down triggered by a magnet or something or space of the gap from the temp of the thermostats copper wire. Anyway above the first disc it is connected to the control knob for heat. Does that knob also serve as my anticipator or is my set up void of one entirely? -Propane

  10. I think it's worth mentioning that setting the anticipator equal to the amp draw equates to about 6 cycles per hour. In many cases with higher efficiency equipment, you want to use a multiplier greater than one to reduce the cycle rate. Honeywell used to recommend 1.4 for heat pumps, and sometimes you may want to use up to 2.0 for high efficiency equipment in a well-insulated home. So in your case 0.35×1.4=0.49 anticipator setting for less cycles. Likewise for short-cycle electric heat you should use a multiplier of 0.6 to increase cycle rate.

  11. Just a note. On older natural draft furnaces where the thermostat only controlled the gas valve then setting the anticipator to the amp draw this method is acceptable. On furnace where the thermostat controls through the non-integrated or integrated control board additional information may be needed. If one checks the data label on the non-integrated boards you may see TH + 0.2 amps. This means if the amp draw on the W wire is 0.37 amps you add 0.2 to that for the correct anticipator setting. In this case that would be 0.57 amps. If you change the ignition control check the TH + rating. If it is not the same you will have to readjust the anticipator. The installation instructions will usually have the correct heat anticipator setting referenced in the instructions or on the wiring diagram. The newer Rheem/Ruud furnaces do not list an anticipator amp draw setting as they want electronic thermostats used. On high efficiency furnaces where the heat anticipator setting is not referenced multiply the W amperage by 1.8. This will usually get you very close to the setting needed when using a mechanical thermostat. When working on boilers multiplying the amperage on W by 1.8 will also work.

  12. A good tutorial, thank you.  I used to do this for a living 25 years ago, and, while I knew I had to check the amp draw etc, I just couldn't remember the fine details on how to do it.  You cleared all that up for me, I metered the white wire, set the stat, and all is working now as it should be.  Good job.

  13. Great video, very informative! I realize you work on only furnaces in your videos but I was curious if you knew if setting the anticipator for a boiler system was the same

  14. I have another tip for avoiding temperature fluctuation in a home with electronic thermostats. If you have celsius/fahrenheit setting it is best to use the fahrenheit setting, because the temperature gradients are smaller.
      Example 20- 21 celsius is quite a larger increase in temperature than say 69- 70 fahrenheit.

  15. Yes. Sometimes, they can be set for longer cycles because the boilers have more thermal mass (they take longer to warm up).

  16. Turn the thermostat temp setting as high as it will go to see if it does the same thing. If it does, the stat is ok and you may have a problem with the furnace itself.

  17. and when my furnace turns on it last for 1 min turns off then it turn on for 7 mins why das it turn on and off for that 1 min thk

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