What is the age of these HP condensers? Have you called your installing dealer? Could be a variety of reasons. Wire size may be undersized. May need hard start kits on both units. I would call your installing dealer and discuss over the phone. I assume both units are heating and cooling satisfactorily. IMO

I have seen a presentation with data collected for the Greenspeed Infinity heat pump. It's quite impressive to say the least. It includes the electrical bill and consumption for a home that has had it installed for 1-winter as follows. Size of the system was not mentioned oddly enough. I would assume it is a 2-ton system. Aug. 25, 2010 to May 11, 2011, 269-days, 8,370kWh @ 8.34cents/kWh = $698 w/Tx - TOTAL, heating, lights, hot water etc included. This was for a 950sq ft (very small!) bungalow built in 1969 with 2-occupants. It is located north of Montreal where heating is required for 70% of the year. Our winters are COLD! Below 0 degrees F is not uncommon. We have over 400-hrs/yr of below 0 degrees F temperatures in our region and even more so where this home is located, according to regional BIN data. According to Carrier, the balance point for a 3-ton Greenspeed (this sounds small to me) installed in a 3000sq ft cottage is about 5 degrees F. For the Canadian winter climate Greenspeed is rated at 44% more efficient than the Mitsubishi Zuba. In cooling mode it's rated at 27% more efficient than the Zuba. Rating (on this slide) was by ecoENERGY, which is a Canadian federal government agency. The data collected in the presentation got quite interesting when the cost of oil heating was compared with geothermal, 2-stage Infinity and Infinity Greenspeed. Greenspeed was 5% less efficient than geothermal, but 12% more efficient than the Infinity 2-stage and 79% more efficient than an oil furnace (efficiency not mentioned). When compared to an all electric system, Greenspeed was 8% less efficient than geothermal but 20% more efficient than the 2-speed Infinity heat pump and 66% more efficient than an electric furnace with no HP. These last 2-senarios (oil & electric furnaces) were represented in dollars only. The 25-slide presentation contained 23-slides of graphs charts & tables. It was prepared by Carrier Canada and was in French only, however 1-slide comparing the Infinity Greenspeed to the Mitsubishi Zuba with all technical data was referenced to the American Heating and Refrigeration Institute (AHRI) so that there should be credibility in the numbers. Hope this helps... SR

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

It would be a real shame to call in another contractor since your present one has become heavly dependent on your business. Yes,you should believe what the service man told you about your neighbors older unit humming in an area where it can't be heard. They redesighned them so the customer knows if the power go's off or breaker trips. If I were in your position where the hum bothered me,I would remove the transformer and remount it with rubber insulation between the mounting base and condenser case. If the noise is coming from the transformer and you press on it the noise will change.