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If I buy Munchkin, can I adjust reset curve?

S Ebels
S Ebels Member Posts: 2,322
On Viessmann Vitodens if you're looking for a good condensing boiler. It programmable more ways than you can use in one one house and comes with a manual that shows how to do it.


  • R. Kalia
    R. Kalia Member Posts: 349

    Do I understand correctly that the Vision I system is kept under such tight control that if I want, for example, to improve the reset curve parameters based on operating experience, I will have to have the installing contractor come by and pay for the visit? They will not give me the documentation or show me how to change any settings?

    Does changing such settings require a laptop, cable and their software?

    Because if that is so, an 'open' system using a Tekmar might be a better choice. Please clarify, thanks!
  • The 925 controller

    that comes with the new Munchkins along with the Vision I kit does not require a laptop, cable or their software to program; only a trained professional. The laptop, etc. is for diagnosis.

    If you were my customer and seemed technical enough to be able to understand the programming, I'd show you how to do it. But you would have to take responsibility for any damage to the equipment. It would be like the first time on a bicycle: you might crash.

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  • R. Kalia
    R. Kalia Member Posts: 349

    Well, I've been on a lot of such bicycles in my time. Anyway, you are telling me that Munchkin does not treat it as a trade secret you may not reveal. I will make it a condition before signing a contract that the contractor will have to show me what to do and leave docs. Thanks!
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    Intelligent vs. Adaptive Programming

    Truly intelligent programming is likely a myth as such implies the ability to take actions (and make errors) not considered by the programmer. Instead, so-called "smart" programming is used--functions can changed based on experience, but they're still perfectly predictable.

    The Munchkin most likely uses some adaptive programaming. As a programmer I know the surest way to mess with adapting programming is to keep changing things so that it never has a chance to establish a "base" and adapt itself.

    The training is there to help installers set up systems that allow the program to establish that base and then adapt. "Tinkering" with the settings won't be a good thing.

    This isn't to say that well-informed homeowners shouldn't be able to make changes but I think changes should ONLY be made after observing operation for quite a long period and then only made in small amounts. Were it me doing the programming I would have set up readily available output for OBSERVATION and written multiple layers of "programming lockouts"--some of which should remain intact for all but the most highly trained.
  • leo g_13
    leo g_13 Member Posts: 435
    hey swampy

    check out this website, and let me know what you think about this approach will you?



    leo g

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  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    Not really sure

    I've looked at it before, the goal and basis seem fine, but I can't find out what it's actually doing to the equipment nor is any information provided on the actual space temperature fluctuation during operation.

    It [seems] as if it will make the circulator and burner operation completely separate with long periods of circulation--but since there's no way it can change the output of the boiler when it's firing, I'd like to see the effect on the burn cycle time--particularly if the temp of the circulating water is controlled as tightly as 5°.

    I haven't a clue as how it is supposed to control the supply temperature of a conventional forced air furnace. Does it cycle the burner as the blower is operating? If so, that sounds really strange and I certainly don't understand how the supply air temp could be anywhere close to constant.
  • R. Kalia
    R. Kalia Member Posts: 349
    my interpretation

    They've tried to confuse everyone with a murky presentation, but I think I get the basic idea. Normally, an outside sensor lets a reset controller determine what the water temperature should be, but only via a reset curve that may not be quite right. Here, instead of an outdoor temperature sensor, their box monitors how long the thermostat calls for heat.

    If it doesn't call for heat very long, the device (which replaces the aquastat just like an outdoor reset controller) drops the water temperature. If the thermostat never seems to quit calling for heat, it raises the water temp. This does not require a reset curve; the thermostat tells you via the duration of the call for heat whether the water temp is too high or too low.

    The only problem is, they think the "Ideal demand ratio" is 60%, i.e. if the thermostat is calling for heat longer than 60% of the time, they raise the water temp. In fact, to get the lowest possible water temp, you need an Demand Ratio of of 99%, which a properly tuned reset curve would provide. But it is hard for this kluge method to control near 100%, much easier to control wih more on/off cycles.
  • R. Kalia
    R. Kalia Member Posts: 349
    Munchkin adaptive??

    > Munchkin most likely uses some adaptive

    > programming.

    The only thing I would want to do on the Munchkin is change the reset curve, since only with experience does one know what it should be (the original design parameters may be lost in the mists of time, or the house may have new windows or insulation).

    The contractor can only guess at the curve, and will probably want to keep a safety margin so that the house won't ever be too cold. This means the thermostat will turn the boiler off now and then. I want to do better than that, so as to achieve the lowest possible water temperature and close to continuous circulation. The only way I know of to do it is to adjust the reset curve based on day-by-day experience.

    If the Munchkin has some way of knowing whether the house is getting cold, and adaptively increases the water temperature to just the right point, that would be great but there is absolutely nothing in their publicity materials that suggests that it has either adaptive or intelligent control or has any way to know the indoor temperature. It has regular reset controller logic. If anyone knows different, please post.
  • R. Kalia
    R. Kalia Member Posts: 349
    at what price?

    Thanks for the suggestion, but we can't afford Viessmanns.
This discussion has been closed.