carl what size systems were discussed? The Infinity heat pumps are two stg and only are available in full ton sizes-no 1/2 ton models. Trane's XL15i HPs come in 1/2 ton sizes from 1 1/2 tons up to 4, then 5 tons. Now to ductwork. Ductwork must be correctly sized to the conditioned air it delivers. Usually it is 400 CFMs/ton both supply and return. So as an example, for a three ton system, you must move about 1200 CFMs of air. If you have a supply leading to the basement, you should have a return. I will assume that the air in basement is of reasonable quality. Ask dealer based on current ductwork system, how much supply air you have and how much return air you have? If you have any hot/cold spots in your home, now is the time to address as they probably are ductwork design/size issues. what is your location? what size are you replacing? IMO

Bald one, thanks. I appreciate being cited by you. Question: Had an RGFD installed in June w/ the '411'. I had hoped that it would have included the DOD feature. I was considering having a humidistat installed to take care of that. I find it strange that there would be 2 new models (of stats) released within such a short period. I had an RARL-JEZ installed at the same time and was told by my contractor that it would work with a humidistat. but I opted to wait to see how it would handle humidity without it. It is a 4 ton unit set up with 3.5 ton airflow. Humidity is O.K., but would like the extra 200 CFM, so thinking about going the humidistat route and setting up for 4 tons, if possible. Your comments, please. BTW, do you think there would be a program to swap a slightly used '411' for a '412'? Thanks. V

The previous top-of-the-line model from Lennox was the HPXA19, so I can only imagine that is the model you would be getting. It was never rated with the brand new G71, so you'd have to estimate using the G61V or similar, in which case the old engineering data shows about a 15 SEER / 7.6 HSPF rating - not very good, but it is two-stage so it may perform better depending on usage. The current top-of-the-line Lennox XP19 only achieves a 16.15 and 8.10 with the furnace you specify and the best matched coil (CX34-62C), unless it is a downflow or horizontal install. The major changes came with the cosmetics, but the new design also provides more surface area so there is more efficiency too. The $2500-3000 price difference is a lot, so it is an interesting option. It was rated at 75 dB, btw. I'd be concerned about why this unit has been sitting around for 3-5 yrs. Get the serial number so you can verify the actual age. I'd call Lennox to make sure this wasn't pulled out of someone else's house and that the warranty is fully intact.

12" return is almost definitely too large for the basement. I have a 6" return in my basement, and I have actually found it to draw ~200-240 cfm (using a barometer) -- plenty in my case with just a few supply outlets. In your case, I have no way of knowing for sure, but I assume it's piped directly (or near) to the inlet of the furnace blower compartment, in which case there is a lot of pressure and it's sucking in a lot of air and making the basement quite negative (not a good thing). So your basement return in that state may have been drawing close to, if not more than, half of the return air the entire system requires. Is the basement floorplan open to the rest of the home or closed off? If typically closed off, I wouldn't be surprised if the basement door had a tendency to close itself when the system was operating. I suppose putting cardboard over half of the grille is one way to reduce its intake capacity. Your older furnace does not (presumably) have a variable speed blower that will vary its RPM in order to maintain a specific CFM setting. That means that while you are noticing more airflow from the rest of the returns throughout the home, in totality your system is receiving less airflow -- no, not a good thing considering your ductwork is likely undersized to begin with. You have decreased its return capacity. To get the SAME (total) airflow from the rest of the returns throughout the home that were not previously drawing as much air generally requires the system to operate at an increased static; with older PSC type blower motors (non variable-speed), this results in decreased airflow. Hence variable speed motors are often termed "constant CFM" as they can adjust (increase) their speed to maintain a constant airflow (cfm) when subjected to as much as 0.8-1.0" of external static pressure (vs. conventional blowers max. of 0.5", which many duct systems are nowhere close to achieving despite it being the standard "design" figure). You can think of the ESP number as a measure of resistance to airflow, in a sense. The fact that you say the (supply?) ductwork is now much warmer is both concerning and telling. It is unwise for me to say much more than that as I am not there to evaluate your system design and give an accurate assessment of the ductwork design/layout, etc. But it suffices to say, with the info you've provided us, your return ductwork is now more restrictive, which would exacerbate any existing airflow issues. You do say it met the set point without tripping the high limit. Please let us know how the system performs as it gets colder out and the system runs more often in its present state. I would like to ask what made you consider replacing the systems (and proceeding to get 8 proposals) in the first place? Are there functional problems with the existing equipment (besides most likely being oversized) or other comfort issues? By now we have at least established that it is likely the existing equipment is a bit oversized and the existing ductwork is marginal -- but that is (unfortunately) exceedingly common on most residential construction. Are you after more efficiency, better comfort, both? It helps us to help you when we know more about your current system's performance. Lastly, I would not factor online reviews into your decision too much. An air conditioner or furnace is not like most appliances (such as a refrigerator) in that the installation practices and quality can make or break even the best equipment selection. There is a good chance that many (but not all) of the negative reviews you read were due to installation errors. This post was edited by ryanhughes on Fri, Nov 22, 13 at 9:51