Using boost temperature and outdoor reset settings on Lochinvar Knight

Discussion in 'Boiler Forum' started by dwassner, Dec 28, 2012.

  1. dwassner

    dwassner Member

    Jan 31, 2012
    Rochester, NY
    I have been trying to set up my new unit and my theory is as follows:

    Keep the set point as low as possible, intentionally 5 degrees lower than what I know it will need to be. Then use the boost temp. in increments of 5 deg. at an interval of 20 minutes. This way it will boost the additional 5 degrees back to what it would have been to begin with and if it doesn't need or use the boost then all the better. This was also my theory with the night set back feature, going down 10 degrees, knowing that the boost temp. will be used, and if it isn't then all the better. I want to set the low set point of the outdoor reset as low as possible and use the boost to fill in the gap between the low outdoor reset low set point and the normal set point. My questions are:

    Would you suggest a different approach?

    I tried setting the boost time to 20 seconds and the set point that is displayed in parentheses on the illuminated display is not changing. I am assuming that the feature is not working. Does anyone have experience with this? I did this because the thermostats were calling for heat for hours and the house would not heat up.

    The manual states that when the outdoor temperature drops below the low temperature of the outdoor reset setting then the set point increases as the temperature continues to drop. Does anyone know the rate at which this happens?

    Thanks in advance
  2. BadgerBoilerMN

    BadgerBoilerMN Hydronic Heating Designer

    Mar 4, 2011
    hydronic heating designer/contractor
    Read and understand the installation manual. The boost in not for everyday operation but for the rare occurrence. Setback has to be done with the radiation in mind. Every high efficiency condensing boiler available in the US features outdoor reset (ODR). This feature raises the system water temperature as the outdoor temperature drops, again this design temperature is determined by available radiation and local weather. It is best for the novice to set the ODR to the match the design temperature for the area in which he lives and the radiation served and leave it at that.

    Most radiant systems will not benefit significantly with set-back and many will not keep up with the thermostat if not set up by an expert. I suggest you set the ODR and forget about set-back. The ODR will save a considerable amount of fuel without thermostat or water temperature setback. In fact, we installed a Lochinvar Knight 4 years ago in a 1924 bungalow located in St.Paul MN. After the gas company came out for the third time to replace the gas meter the homeowner informed them that the new boiler was the reason for there fuel consumption dropped by two thirds. On this unit we did not setback water temperature since the boiler was sized very close to the heat load and lacked the extra output necessary for any kind of boost.

    Given a choice, I always design hydronic heating systems to run full time without fancy controls strategies most of which should be left to professional designers working on large homes or commercial structures.
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