"we have noticed great temp control, but high humidity in the house." Does your unit cycle frequently? A properly sized unit should run (almost)constantly at design temperature. Fort Worth = 99 degrees. " Even with the fan set on auto, the fan runs @ 90% of the time. " Do you mean your a/c is running 90% of the time? A little confusing. V

I have owned this Maytag 23 SEER IQ Drive equipment from Nordyne (both a 3 ton & a 2 ton unit)since April 2009. I replaced two old, inefficient systems in their entirety. I paid top dollar for this high efficiency equipment and boy was I taken! Lots of service calls (more in 1 year than in the 11 years I owned the older units); high humidity inside the house (a new problem that started with the install of this equipment); noisy fans that wake me up when the units shut down at night; no improvement in energy efficiency at all (I have to keep the house 4 degrees cooler than with the old equipment to keep from sweating, due to the high humidity); equipment is sensitive to power fluctuations (computer brain flips out every time there is a switching transient from the power company and must be reset); and the list just goes on and on. I would NOT recommend purchasing this product. A Trane 2 Stage system would likely be a much better investment (note: I have never owned Trane equipment and I don't know anyone who works for Trane - it just happens to be the alternative I investigated before deciding to buy the IQ Drive.)

Thanks Tigerdunes for the info. I am going to meet with my HVAC installer on Thursday to talk about how best to decrease the airflow while the compressor is on to allow sufficient water to be condensed from interior air -- with goal to keep my internal humidity below 60% (or more). Re your comments 1-4: 1. No crawlspace, house is 9 ft elevated on stilts. I do have a vapor barrier on bottom of R-38 batting in floor. 2. I never run fan in "ON" mode, however, it runs a whole lot on slow speed without compressor running in "Auto" and/or "Cool" mode -- which I think may increase the humidity like "ON" mode as noted by contributors in this forum thread. However I must solve the more major problem of not removing sufficient humidity when the compressor IS running on, first. Then address this if high humidity is still an issue. 3. I agree that attemping to re-program dipswitch settings, even with the manual, is foolhardy for a person not trained in HVAC and Trane eqpt. in particular. 4. Will attempt to get air handler air speed to be more correctly matched to dehumidification needs. Especially in light of your and ryanhughs comments: "First, that air handler will come factory set for an airflow suitable for 3.5 tons, so it should be adjusted for both the high and low stages of your 3 ton unit (4TWX6036 is a 3 ton). Second, is Comfort-R enabled?" Thanks again to all for your continuing assistance. I will post how this does (hopefully!) get resolved. KR

I realize that this is an old thread, but folks may review it in the future and benefit from the discussion. Indeed, there is another, recent, similar thread on low indoor relative humidity in a Minnesota home in winter, so it worth correcting some of the misinformation on this thread. "Again and hopefully for the last time you can not dehumidify with a single stage AC to any large extent. It will always over cool, long before it dehumidifies to any large extent." A properly-sized air conditioning system-- including single-stage systems-- will dehumidify air whenever the air temperature leaving the coil is at or lower than the dewpoint temperature. In the summer in my (mixed-humid) climate zone, that's most of the time. I have a single-stage air conditioner. All of the water being drained at the end of the condensate line is ample evidence it's dehumidifying. In fact, it creates a wet spot in the lawn that I need to reseed every fall. When my air conditioner doesn't do an adequate job of dehumidification is during so-called "shoulder seasons" when there is no real demand for cooling (you can't dehumidify if it's not operating.) We get shoulder seasons for three or so weeks each spring and fall. For shoulder seasons, I've found dehumidifiers to be the right complement to my air conditioner. I have one on each level of my home integrated into the HVAC system. They enhance comfort, and they reduce the potential for mold/mildew which is very common in our climate zone. They can also be configured to introduce fresh air into a home, which is a plus, year 'round. "Just because an AC can't dehumidify a high humid situation, doesn't ever mean it is over sized... because the single stage AC wasn't designed to dehumidify. It was designed to COOL" Not so fast. An air conditioner, as the name implies, is part of a system which maintains comfortable indoor conditions for the occupants. It cools, dehumidifies, and moves air throughout the home. The dehumidification part is stripping moisture from the air. Indeed, when designing an air conditioning system, we need to consider both the sensible cooling load and the latent (moisture removal) loads. A properly-sized single-stage system can dehumidify air. Its ability to do so is affected by run time under particular conditions, which is a sizing consideration.