Anticipator Setting

Discussion in 'General Discussions' started by Blake Clark, Jan 18, 2012.

  1. Blake Clark

    Blake Clark Member

    I'm a bright guy, but I'm second guessing my understanding of Water Furnace t-stat anticipator setting. Here is the language in the manual:

    ANTICIPATOR This adjustment controls the sensitivity and cycle rate of the thermostat. Higher numbers decrease the cycle rate. Lower numbers increase the cycle rate. Default value is 0, and the range is 0-4.

    Here's my situation. My house has two zones, daylight basement and main floor. The basement heat comes from the ceiling with a floor return. I want the t-stat in this zone to be "less sensitive" to heat changes in the room. Basically I want it to overshoot the set point to allow time for the heat to reach the floor.

    In the main zone, for some reason the t-stat seems to be in a "dead zone" and rarely reflects the actual room temperature. I want this t-stat to be "very sensitive" to minute changes.

    I've done what I can with offsets and differential settings so all that's left to tweak is the anticipator setting. I won't comment on how I have them set now, because I don't want to bias responses. How would you set them to do what I'm trying to do?

    PS - this is not at all critical to my comfort or system performance, it just bugs the **** out of me that I can't figure it out.
  2. geome

    geome Member Forum Leader

    Typically more cycles narrows the temperature range (for example: keeping the temperature range within +/- 0.02°F of the set point), and less cycles widens the temperature range (for example: keeping the temperature range within +/- 1.00F of the set point.) This could be called sensitivity. How this interacts with the differential and other settings involves the specific (proprietary) thermostat programming.
  3. Blake Clark

    Blake Clark Member

    So, I think I understand the theory O.K., it's the term "cycle rate" that is throwing me - it's just not clear to me which direction to move the numbers to achieve what I want.

    How I read it is that I would want my upstairs t-stat set at 0 and my downstairs t-stat set at 4. This is my best read of the instructions and how I have them set. But In practice, either I have them backward or the setting doesn't really make that much difference.... I can't get the downstairs t-stat to overshoot and the upstairs t-stat takes forever to respond to room temp swings, even though I have the differential set at 0.5 degrees.
  4. geome

    geome Member Forum Leader

    I believe your anticipator settings are consistent with what you are trying to accomplish, but whether it will actually help or not is another matter.

    For the basement -
    Instead of adjusting these settings, why not either increase the thermostat set point 1 or 2°F, or reduce the temperature display offset by 1 or 2°F?

    For the main zone -
    Can the thermostat be moved to a more appropriate location, or can you use a remote sensor?
  5. Blake Clark

    Blake Clark Member

    Thanks for checking my logic.

    For the downstairs t-stat I found that changing the offsets and the differential didn't really do much either. The real problem is that the system is oversized for this zone so very warm air reaches the t-stat in relatively short order. It's not enough time for the room to fully circulate through the bottom return register.

    What I found when I increased the differential was that when the warm air from the ceiling works its way down and hits the t-stat it jumps multiple degrees quite quickly. So unless I have the differential set for 3 or 4 degrees it doesn't help much. What I really need is a timer function that keeps the unit running for 5 minutes or so after it reaches temp (i.e. when the heat is "half-way" down to the floor. I thought I could approximate this with the anticipator setting but it seems with minimal results.

    Short of this, my workaround is to set this zone for economy so that it has to wait for another zone or for a stage 2 call. By whatever fuzzy logic the t-stat uses when it shifts gears from stage 2 call to stage 1, it'll stay in stage 1 for a awhile even if its reached temperature. Plus when another zone is running, the air temp out the vent isn't so warm.

    I know t-stats are supposed to be much smarter than they used to be, but I wish I had more control over how it goes about its business.
    Last edited: Jan 22, 2012
  6. dgbair

    dgbair Just a hobby Forum Leader

    Have you tried just letting your fan run all the time? Maybe this will help circulate the air more and give you better results?
  7. Blake Clark

    Blake Clark Member

    Yes, the fan the fan is set to run continuously in both zones.

    I've learned zoning is more complicated than I first thought. The heat balance in the house, i.e. ductwork and airflow, is very good when it is cold outside and both zones need heat. When the upper level warms up, though, - solar gain, cooking, etc - the basement zone is on its own. Even though there is more heat going into the basement during these times it's actually more comfortable down there when both zones are calling for heat.

    I work from home and my office is in the basement zone so I start to notice all these little things...
  8. WF_Inc

    WF_Inc Member

    Our thermostats are not designed to overshoot the setpoint. There is a 30 minute algorithm in the logic board that will tell the thermostat to upstage. Once the set temperature has been satisfied, the unit will power down.

    The cycle rate is the maximum number of times the unit will run in an hour. We would suggest that this be left at the factory default setting.

    With a zoning system, we suggest that the comfort setting always be used. The economy setting will try to satisfy the set temperature without using the compressor.
  9. Blake Clark

    Blake Clark Member

    Thanks WF, at least you confirmed what I'm experiencing. You misunderstood my question about cycle rate - it is how cycle rate is related to the anticipator setting that is confusing. I'll ask another way - what exactly does the anticipator setting change in terms of t-stat functioning? Is it a redundant control that manipulates cycle rate directly? Also, entering numbers above 4 is possible, which then seems to alter the offset.

    What totally bugs me about plug and play is that the device is not usually nearly as smart as the designers think it is. What the t-stat is doing behind the scenes - some of us would like to know the logic. I'll agree that a smart device can get 80% there, but they generally utterly confound and roadblock those of us trying for the last 20%.

    For example - I wanted my upstairs AC setting to upstage the fan speed between a stg 1 call and stg 2 call. Stage 1 call being low speed for dehumidification and a stg 2 call for higher sensible loads. I want to do this without upstaging the compressor. Seems like a no-brainer to me for comfort and efficiency. Good grief - I finally figured out how to circumvent the zone board logic but why should I have to implement a workaround for something so basic?
    Last edited: Jan 24, 2012
  10. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader



    I enjoy your posts, you have rare insight.

    Since WF is in on this thread I will not tell you how to work around the main board logic and "fool" the ECM blower into thinking it is in second stage.

    I know for sure you will not get what you want by fooling around with the heat anticipators. The heat anticipator was designed to fool the thermostat into thinking it had reached set point. It was an electrical coil that warmed the bi-metal spring that turned things on and off. With a scorched air, I meant forced air, system if we waited for the wall to reach set point the unit would heat the air beyond the set point. Bill and Steve had not been born so the guys put the little heater in the thermostats to anticipate hitting the set point.

  11. Blake Clark

    Blake Clark Member

    We can compare notes - your workaround vs my workaround. I'll I can say is that its a good thing there were a couple of empty zones on the board.... :D
    Last edited: Jan 24, 2012

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