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Anticipator setting?

Converted gravity system with large diameter cast iron pipes, cast iron radiators, 4 years into a Munchkin mod-con boiler with 925 control panel.  2 zones, main house and radiant floor for kitchen plus adjacent. No outdoor reset.   Thermostat is a White-Rodgers <span>1F97-371, a simple 7-day programmable (manual at </span><a href="http://www.white-rodgers.com/wrdhom/common/ptech/thermo/90_Series_faq.htm#26">http://www.white-rodgers.com/wrdhom/common/ptech/thermo/90_Series_faq.htm#26</a>).

The house is warm, doing OK there, but the boiler short-cycles a bit, although I'm not a pro. The panel readout says 1,000 central heat hours, 27,500 passed ignition attempts, 35,300 total run time hours ( = almost exactly 4 years). Only 1,000 heat hours over 4 Iowa winters???  At any rate, 30 ignitions per hour sounds like short cycling to me (how many per hour is good?). I'm assuming it does not count the many many failed attempts when I was dealing with F09 issues last month.

I just learned that the thermostat has adjustable anticipation, range 0 to 40. The manual says "start at setting of 35 for hydronic" but it has been set at the factory default of 5 for the past 4 years now. I recently learned/corrected some installation mistakes made with the Munchkin, is this a mistake with the control settings on the thermostat?

Basic question is, any thoughts on an appropriate anticipation setting for the t-stat, and/or how do I figure out if I am at the right setting if I "start with 35" as suggested?


  • Jamie Hall
    Jamie Hall Member Posts: 21,093
    A higher anticipator

    setting on this unit will lengthen the cycle time.  In fact, going from 5 to 35, it should lengthen it quite a bit.  How much?  Dunno.

    The trade off is that the temperature may vary more -- but with converted gravity system, there is a lot of thermal mass in there between the water and the iron, and I would imagine that the temperature variation will not be all that noticeable.

    Ideally with an anticipator, the thing should be set so that the system shuts off before it actually gets to the set point temperature, and the remaining heat in the system is enough to bring it up to, but not over, the set point.  That's the theory.  Doesn't always work out that way, and that may not be the best anyway.

    How do you know if it's right?  Temperature stays pretty even and the cycle time is as long as possible -- once per hour, I'd say, with a converted gravity.

    I have a feeling that those readout numbers may not mean what they seem to mean...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ErikV
    ErikV Member Posts: 34

    OK I set it to 30, going to see how it behaves. Going out of town for a couple weeks so my wife will have to tell me how it goes. I'm thinking that if temp still holds steady, maybe the boiler is cycling longer with the higher setting so that is an improvement. Thank you for the explanation of what the anticipator control does.
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