My 2052 square foot (first and second floor) colonial was built in 1986. I live in Bel Air which is about 20 miles north of Baltimore, Maryland. I moved here in 1993 and in 1996 converted from a heat pump to a natural gas furnace (Carrier 92% efficiency � 80,000 BTU) and a new AC unit (Carrier 2.5 ton unit 13 SEER). The Carrier gas furnace has two cracks in the primary heat exchanger so I am planning to replace the entire system before the fall heating season.

Attic insulation is R-30.

Cost per therm of gas: 0.49710000 cents

Cost of electricity: 8.857 cents/kWh through September 30, 2014 and then 8.616 through May 31, 2015

My goal is a trouble free system that keeps me cool in summer and warm in winter. I am not too concerned about saving money but I do not want to spend money foolishly. Since my system is already fairly energy efficient, I don�t think I can really count on much cost savings.

The only minor complaints I have about with the house is that the humidity in the basement is high (just smells musty � no mold or actual condensation) so I am running two dehumidifiers (one in laundry room and one in storage room).

Also the second floor has condensation on windows in the winter that causes mildew on the bedroom and bathroom windows (white painted wood on inside). I suspect that is from humidity from showers and baths. I am planning bathroom renovations that include bathroom exhaust fans to supplement the bathroom windows.

Also the second floor is sometimes warmer than the first floor in summer. I installed an attic fan that is on a thermostat and that has helped enormously. This has been a cool summer so I have not noticed it at all this year but there is still a temperature difference when it is really hot.

The basement is partially finished and the HVAC has two supply vents and one return - all in the ceiling bulkhead. Both contractors that have been here (I only have one estimate so far � I am waiting for an estimate from one and one more contractor is coming tomorrow) suggested running the fan all the time in the summer to mix the air and remove more humidity from the basement and also to mix the cooler air from the rest of the house to better cool the second floor. I am hoping running the fan is less costly that running the dehumidifiers.

Here are the two proposals from the first contactor:

Both proposals are for a Carrier 3 ton air conditioner and have a 10 year parts (including compressor)/5 year labor warranty from the installer, besides Carrier�s warranty which I think is only one year labor. Lifetime warranty on the heat exchanger � not sure if that is from Carrier or the installer.

Proposal #1:
AC 24ANB 636 16 SEER/13EER
Furnace 59TN6AO80V17-14 96% 2 stage ECM
Coil CNPUP3717ALA
Thermostat Infinity Touch (WiFi)

Net cost to me after various rebates and discounts: $7928

Proposal #2:
AC 24ANB636 16 SEER/13EER
Furnace 59TP5AO80E17-16 96% 2 stage
Coil ONPUP3717ALA
Thermostat TP-PAC

Net cost to me after various rebates and discounts: $7248

The price above includes installation of new refrigerant lines, install new condenser pad (current AC unit is too close to house and code now requires it further away), use existing condensate drain, reclamation of existing refrigerant (R-22 � new system uses R-410A), new line set, all permits, necessary gas piping to new equipment, Schedule 40 PVC vent piping for intake and exhaust of condensing style gas furnace to connect and test (I think that are using what is there and will just test it), removal of existing equipment and debris, required modification of existing air distribution box PLUS one return register in basement with grill near the floor.

The price also includes a drain pan and a wet switch - is this going to drive me crazy? I recall he said something about it being sensitive. I only had a leak once when something clogged and it wasn�t a ton of water � this switch will shut of AC if it senses water. I think I would prefer a leak to no AC.

Which of the above systems do you prefer and why?

I have an old Aprilaire Model 560 that can be replaced with a new Aprilaire Model 2200 at an additional cost of $395. Contractor #1 said replace it as they are no longer making it and parts might be hard to come by. Contractor #2 says keep it and was not concerned about parts.

Should I do the return in the basement at floor level?

Both proposals include keeping the old air filter that I have � a Spaceguard High Efficiency Air Cleaner 2200. Keep? Replace? Both contractor said keep. I have a maintenance contract but they charge me for the filters for this and pads for Aprilaire humidifier ($118 total when last changed � changed once a year).

Is the AC a two stage model? Contractor number two (waiting for proposal) said he did not think that was a good idea for my house.

According to contractor #1, Manual J says 3 ton not 2.5 ton AC as is currently there. He used 15 degrees for heating and 95 degrees for cooling as design temps. He also said Proposal #1 is better at dehumidification. He said he recommends Proposal #2 due to price differential ($680).

Contractor #1 is also looking into whether Carrier will pay anything for the job under heat exchanger settlement. There was a lawsuit about early failures.

Contractor #2 will be bidding American Standard equipment. How do they compare with Carrier? I might never move but I have been toying with the idea and Carrier has great name recognition although I did check and Consumer Reports likes American Standard just as well.

I think Contractor #2 might be planning to use the existing line set. Wise or unwise?

Thanks!