Thanks for your input. I would estimate the living area for the main floor and finished basement to be around 2,900 sq ft. We are replacing a 3 ton 10 seer AC. I think the furnace is 70,000 btu. I met with another company yesterday, and I liked this company the best. I still would like some advice though. We are leaning towards the following option, which he recommended: Carrier 58CVA090-16 Infinity series variable speed furnace Carrier 25HMB636 Infinity series 3 ton/16 seer two speed heat pump The total installed price quoted is $8,855. More than we wanted to spend but Carrier's extended labor warranty for years 2-10 is rolled into this price. Is the extended labor warranty recommended? On another company quote it was listed separately at $650 and I don't know if that is something we should try to negotiate out of.

Those prices seem a little high but it depends on your area and I really can't answer that. Get quotes from another company to compare. Don't let a "lifetime" compressor warranty make that system sound better than any others. That compressor is the same type used in most systems- (copeland scroll). Since the average system lasts 12-15 years, what good does it do to put a new compressor in a worn out old system? Does the warranty cover labor and materials which can run hundreds of dollars anyway? It's a nice selling point for them though. Why not a lifetime warranty on the components that go bad first, like the indoor coil and motors?

So yesterday buddy comes over to look over things with the a/c system and I think we've got things nailed down properly now. The superheat for the given ambient temperature and heat loading from the indoor coil was way off (5F) vs. the 14-15F that it was supposed to be so he had to remove some of the refrigerant (I was quite surprised how little he had to remove to get the superheat up) and we even went as far as measuring the furnace's CFM flow rating using a differential manometer. I'm pushing roughly 1000CFM across a 2 ton coil so which is a tad bit on the high side but my colleauge says it's a margin of safety for the a/c to not freeze over as we have relatively little humidity in the air would means that on the cooler days we wouldn't be heat loading the coil enough which could lead to freeze up. I personally would like to try running my furnace on the lowest speed to get the 855 CFM but I'm not sure how that will affect the superheat. Presumably I would imagine that if a system is charged properly using the superheat method for fixed orifice systems that blower speed shouldn't dramatically impact the superheat values to the point where they're completely out of whack. I would guess that superheat would rise but isn't that sort of a given? I mean hotter days for example would increase loading so therefore superheat should rise no? For the record the pressure reading on the manometer with the furnace on medium low with a 3M 1500 series filter installed has a -0.44 in wg static pressure difference. With no filter the static pressure diff changes to -0.55. Humidity was still somewhat of an issue yesterday night when it was raining but it was quite cool outside. I had to drop the tstat to 21C to force start the a/c on but after just 20 minutes the house was nice and dry and less stuffy. Just for the sake of my understanding does TXV technically do any better or worse job of temperature/humidity control over a fixed orifice system IF both systems were installed properly and charged to near perfection? I have a friend that is looking to install a/c and his contractor insists on having TXV and says that fixed orifice is evil and should never be used. I find that rather extreme to make a claim like that. I've tried to do my own research online and although it's a given that TXV is the way to go I think it has a lot to do with the fact that it will better protect the compressor from liquid flooding + it's more forgiving for techs that do an incorrect charge on the system - critical charge isn't nearly as important on a TXV system vs. fixed orifice. Thanks,

I just purchased a trane xl 20 I 4 ton heatpump . With the xv 80 furnace with the trane matching coil and a trane 803 thermostat. With out door sensor. It is designed to run as a duel fuel system. I think the company installing this unit did not have enough experiance in a duel fuel system. They have been back several times and still are having a hard time, The heat pump was working fine as the temperature dropped to below 32 the unit was not turning over to the oil heat. Also the outdoor temperature on the thermostat was showing 80 degrees. They just left and they reprogrammed the thermostat and did a few things that have got the themostat to read the correct outdoor temperature. I hope now it will work. What temperature should the trane heat pump cut off and the oil furnace come on?????? How do I know if this system is installed correctly? They have come back 6 to 7 times. For this and that. I have lost some what faith in the company. Should I find a company to come and check there work. This is a dual stage sophisticated system by trane. I did get a great deal but have paid a price in the level of headache. Any suggestions would greatly be suggested. Thanks.