Does sound high, but you didn't say whether it involved any ductwork modification or any other extra work/materials. Best way to get a feel for prices in your area is to get 3 or more estimates. The Infinity is a top of the line system, and maybe that's not what you're looking for (less expensive systems can do a fine job keeping a home comfortable if installed and selected correctly). Provide some more details on the estimate if you have them or if there is any more to share (just a straightforward changeout?). I would expect more in the $8000 range for a 4 ton Infinity system with gas heat and all associated labor/materials. I'm not a professional myself, and I'm in Maryland, but that's my perspective based on what I've seen.

pablo I think this system is overkill. I assume existing system is also three ton. correct? if upfront cost is a concern, look at the following sgl stg system. while not all the sophistication and bells/whistle of the two stg Infinity system, it will do a very nice job keeping you comfortable. see below. and it does qualify for the tax credit. the Infinity is straight AC not a heat pump? correct? Performance 15 AC with vs air handler. 1348229 Active Systems PERFORMANCE 15 PURON AC CARRIER AIR CONDITIONING 24APA536A30 FV4BN(B,F)005 36200 13.20 16.00 1 pair with a Carrier thermidistat and box 4-5" pleated filter cabinet and you are ready to go. I assume you will use strip heat when/if heat is required. correct? IMO

I am familiar with the area/climate, and I too believe that the equipment is oversized and will not perform optimally, especially the first floor system. Very common (and outright wrong) practice in the residential HVAC industry. I would not move forward without a load calculation. When you are given a written copy of a load calculation, post it here if you can. The 005 is the better matching fan coil size for the upstairs system. Same physical size as the 003, so space isn't an issue. I am also quite certain 15 kW of strip heat for the upstairs system is excessive as well. Sounds crazy for an upstairs heat pump system conditioning ~1200 sqft. I have 15 kW of back-up strip heat for my 4 ton heat pump system, which more than adequately conditions my entire house (~3000 sqft total) in MD. You've been quoted quality equipment at a fair price, I would only caution you to verify that the equipment is properly sized to your home's load. This results in the most efficient, reliable, and comfortable operation. Just as important as finding a qualified and competent company to do the work and provide exceptional service following the installation. This post was edited by ryanhughes on Sat, Sep 7, 13 at 19:32

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