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  1. #1
    Join Date
    Jul 2007
    Posts
    21

    Furnace stages & humidity/humidifiers

    2 heating questions.

    Furnace stages. We have a 2 stage variable speed American Standard furnace with an American Standard 2 stage programable thermostat. Since we're in an out of the house without a typical schedule, we don't program the thermostat, but manually make changes. The problem is that the first stage that comes on is the high stage, which blows really hard. First, shouldn't the lower stage come on first and then the more powerful stage only if necessary? Second, it seems that the lower stage is really sufficient. If so, is it possible to have the furnace or thermostat programmed to only work in the lower stage? Wouldn't longer lower runs increase comfort - especially in a house like mine: 100+ years old, somewhat leaky, with old ducting that leads to variable temps throughout the house?

    Related somewhat is a humidity question. When the furnace blows the house gets uncomforably dry,with our throats getting itchy and our scalps dry. To remedy this we just got an aprilaire bypass humdifier installed. I haven't checked the humidity levels, but it's only the beginning of the heating season here in the northeast, and the heating is already drying us out. Would longer runs allow the humdifier to work longer, thereby increasing the humdity levels?

    THANKS

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,466
    Some stats run on low for a while to see how well low is doing catching up. Most go to high if there is more than about 1° temp difference. Using the program feature will result in longer low runs.

    As to humidity, yes.

    Note that the furnace doesn't DRY the air. What happens is warm air can HOLD much more moisture making the RELATIVE HUMIDITY low. So as cold air leaks in and is heated, the RH% drops. Slow or stop the infiltration, you reduce or stop the dryness.

  3. #3
    Join Date
    Jul 2007
    Posts
    21
    Quote Originally Posted by BaldLoonie View Post
    Some stats run on low for a while to see how well low is doing catching up. Most go to high if there is more than about 1° temp difference. Using the program feature will result in longer low runs.

    As to humidity, yes.

    Note that the furnace doesn't DRY the air. What happens is warm air can HOLD much more moisture making the RELATIVE HUMIDITY low. So as cold air leaks in and is heated, the RH% drops. Slow or stop the infiltration, you reduce or stop the dryness.
    --------------------------------------------
    Although our infiltration is higher than we'd like, we've done all we can to reduce it (recently blew insulation into the walls, weatherstripped the single pane windows, and added new top notch storms...), still old houses are old houses. So, our only choice seems to be adding humidity to the air. I was reading in another post a question about running a powered humidifier with the furnace fan on. Ours is not powered (we have Aprilaire 600 bypass) and I was wondering if running the furnace in fan on or in continuous mode (on 35% of the time) would help keep the humidity at more comfortable levels? I read somewhere else that to enable the humdifier to work with the fan running (and no call for heat) that special wiring is required, but I'm wasn't sure if this was accurate.

  4. #4
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,305
    Since we're in an out of the house without a typical schedule, we don't program the thermostat, but manually make changes.
    My hours are vary as well since I am in Retail.. But I still set the program to about what my hours may be. How vary is your hours?

    First, shouldn't the lower stage come on first and then the more powerful stage only if necessary?
    The 1st stage will only come on if the temp is near set point. but if over, then yes it will go into 2nd stage right away.

    Second, it seems that the lower stage is really sufficient. If so, is it possible to have the furnace or thermostat programmed to only work in the lower stage?
    You could make it only work on 1st stage, but in recovery on a very cold day, you will have to wait.
    Wouldn't longer lower runs increase comfort - especially in a house like mine: 100+ years old, somewhat leaky, with old ducting that leads to variable temps throughout the house?
    Yes you are right about long run times. But when you manual change the temps, most people want the temp to get up soon as it can, not wait.


    Ours is not powered (we have Aprilaire 600 bypass) and I was wondering if running the furnace in fan on or in continuous mode (on 35% of the time) would help keep the humidity at more comfortable levels? I read somewhere else that to enable the humdifier to work with the fan running (and no call for heat) that special wiring is required, but I'm wasn't sure if this was accurate.
    You could do that. but depends on how the installer wired up the humidifier, if they wired it on the HUM, it will only run when the heat is called for.. if they went on ACC/EAC, then it will run any time the blower runs.

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