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  1. #1
    Join Date
    Jul 2006
    Location
    Las Vegas
    Posts
    34

    Can oversized Lennox 3 Ton/2-stage AC be adjusted to run like 2 Ton unit?

    Hello. I live in Las Vegas. I have a 3 ton Lennox HSX19 2-stage AC and 60V variable speed blower, and VisionPro 8000 stat, installed in my home in summer 2006. I have been having ongoing short cycling issues with its set up. First and foremost I will say it is oversized in my opinion. I did not discover this forum until after the fact. No Manual J was done and was told by the salesman that this was perfect size unit based on a 400sqft per ton “calculation”. My single level home is only 1165sqft. They are an exclusive and large Lennox dealer in the area.

    I wanted to know if the AC could be configured to run exclusively in first stage to attain longer run cycles, and to prevent it kicking on for so many intervals a day? I was only getting 6-8 minute run cycles when I first got it, and no condensate draining out at all. I complained many times over the months and their tech came out to see if he could make any adjustments. The last time out he discovered some “red wire” that was not connected properly, causing the AC unit to jump straight into second stage at start up without running in first stage at all. Great. He said he fixed that, but still wonder what that issue really was.

    I have now been getting run times closer to 20 minutes each before it shuts off for 10-15 minutes or so. I also started seeing water drip out the condensate drain. However, I still believe run times should be much longer according to most posts on this forum…at least 30-40 minutes each cycle, or am I wrong? I understand even a properly sized AC unit can be running almost continuously depending on various factors to meet or maintain a temperature set point.

    I am concerned about it, since I’m stuck with it for the next 20 years. I like the unit itself, and seems well made compared to some units I have seen. It is a larger unit with a huge fan blade, and is very quiet standing next to it. But I am still a bit worried it is not set up for optimum operational efficiency and energy/cost savings that I desire. Since mine is a 3 ton 2-stage unit, shouldn’t running first stage alone be able to emulate to the equivalent of a 2-ton unit, and perhaps adjust for its being somewhat oversized? Are there any other key adjustments I can have the installing company’s tech look into before I call someone else in? Is there a monitor or thermostat device I can buy that indicates the current stage it is running in? Appreciate any feedback on these issues!! Thanks. - Ken

  2. #2
    Join Date
    Feb 2008
    Location
    Dallas & Longview, TX
    Posts
    629
    The outdoor temps. are not at there highest this time of year. In the hottest of summer temps. see if you don't get longer running cycles. It may be closer to what you were expecting. Regarding setting the speed to stay on low, I'd call the contractor that installed it.

  3. #3
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,748
    it would be very easy to install a high speed "lockout" switch that would keep it in low but give you the option of high if needed.

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,171
    In first stage its closer to 80% then 70%. So 80% of 3, is 2.4 tons.
    The Honeywell IAQ doesn't go to second stage until it determines that the heat load is at 90% of first stage capacity.

    At 30 minutes run time, its running close to what it should. They may be ale to slow the blower down to get a slightly lone run time.
    But keep in mind that at low OD temps, it won't always have a long run time.
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