The lower system currently has switchable electric or hot water as auxilary heat (currently an oil fired hot water heater is acting as a boiler). The end goal is to have a true boiler installed to feed the 'hot water heater/exchanger', the downstairs water coil , the upstairs water coil, and a bonus room above the garage that is not finished yet.. (so 3 separate systems) I was looking at zoning the new upstairs unit to include the Bonus room, but the trane guy talked me out of it. The room is sandwiched between an attic and a garage, so the most comfortable solution was believed to be a separate system. Electric heat is expensive. Oil is also expensive, but the btu output is high making it an attractive alternative. Each system has it's own return. So the hallway return is just for upstairs air handler. I had a clean effects installed on the lower system when it was replaced and was unimpressed. Sorry for adding more confusing info, but hey if it helps... As far as thermostat, all that was mentioned was a "Trane touch screen programmable comfort control", if more detail is needed, I can ask. I'll have to check with the Am. Std. guy about his part numbers.

wayne first off you are undersized on return. If I understand correctly, I personally think you would be better off adding a return rather enlarging and having just one return especially for size of your home. here are the numbers on system quoted. 3221082 Active Systems XL20I WEATHERTRON TRANE 4TWZ0036A1 4TEE3C04A1 36600 13.00 18.60 35200 9.00 19400 there should be no humidity issues with this system assuming you are sized correctly. I am not a fan of these two stg systems mainly because of price. However, it does seem you are getting a good price albeit still expensive on Trane's top of line XL20i with communicating air handler and stat. Here is a suggestion for a substitute system, the sgl stg XL15i. 1384031 Active Systems XL15I WEATHERTRON TRANE 4TWX5036A1 4TEE3F40B1 37400 12.70 15.00 36200 9.00 23400 You would want HW VP IAQ stat with this system. I do not like Trane's CleanEffects. Go for the HW 200 air filter or Trane's Perfect Fit 5" pleated filter media cabinet. I prefer metal trunk lines with flex supply runs. R8 insulation. what size heat strip-7.5 KW? I would verify sizing and request a load calc in writing. I don't want to be borderline in Hot Florida. how would you describe your home's insulation qualities, windows, etc? IMO Good Luck!

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

Cigar Several questions. What is zip code for gmother's location? Describe typical winter climate. What size is system you are considering replacing? It is difficult to believe that a 5 ton is correct size if home has reasonable insulation qualities. I have never particularly liked the Heritage 16 (Trane XL16i). Note the relatively poor BTU output in both cooling and heating for system you listed. If money is no object, you might look at Carrier's new Greenspeed HP system. I am not advocating it, just informing you. It has high HSPF for an air source HP. There are three reasons for needing a properly sized heat strip. 1. To temper supply air when HP is in defrost mode 2. To add supplemental heat on cold days where HP by itself can not maintain indoor thermostat setting 3. To provide emergency heat in case of mechanical breakdown of outside condenser. What size is existing heat strip? Here is my general spec sheet for new system. both outside and inside units should be replaced to have a properly matched system. 15 SEER, 12.5+ EER, 9 HSPF best matching VS air handler full BTUs in both cooling and heating for your rated size R-410a refrigerant(same as Puron) scroll compressor preferred electronic demand defrost preferred thermostat with "dehumidify on demand" feature staged backup heat strips new and correctly sized refrigerant lineset 10 yr warranty on parts and compressor you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc. any hot/cold spot issues in your home should be addressed. My personal recommendation is Trane/AmStd, Rudd/Rheem, and Carrier/Bryant. Depending on your location, I would not purchase a new system that did not have electronic demand defrost. Post back. IMO