Thank you in advance for reading my post. I am new to the site and need some advice as I am in the middle of replacing my heating and cooling system. I live in the Boston area and have a relatively small 2-story house (1,300 sq feet) plus a basement.
My current system is a Carrier 10 SEER 3 ton R-22 condensor and an Armstrong 80K BTU oil fired furnace (in basement). I am looking to switch over to gas. My conractor did a manual J-sizing of the house and is recommending a 2 ton American Standard Allegiance 16 SEER two stage air conditioner and a American Standard 3 ton 60,000 BTU 96.7% Ultra High Efficiency 2-stage furnace.
I have a couple of concerns I was hoping to get some advice on:
(1) The equipment seems much smaller than what I had. I know that my equipment may have been oversized but what risks do I run if the new equipment is undersized? I don't have a seperate unit it the attic like most new houses do to cool the second floor and I use to have a 10+ degree temperature differential between the first floor and second floor during the summer. I had someone come out and look at the system and I was told that my duct work was "unbalanced". The HVAC technician closed some vents on the first floor and that seemed to greatly help in cooling down the second floor. American Standard makes a 2.5 ton condensor as well but it is single stage compressor and only 15 SEER. I wanted to consider intalling this one to make sure the house would proprerly cool down on the second floor (as you may be able to tell I am afraid of moving down a whole ton based on my prior experience above).
(2) I also heard that the system should be properly matched (condensor, coil and furnance). Does that mean if I have a 2 or 2.5 ton condensor that the coil and furnance both need to be the same tonnage? The current proposed configuration would have a 2 ton condensor but a 3 ton furance.
(3) I would like to move up to a 80K BTU 95% American Standard 2-stage furnace as we are going to add a register in the basement to assist in heating it. The furnace produces 49.5K BTU's on the first stage which I would think would make it run on the first stage more often if it is slightly oversized which I would think would be good. What drawback is there if any if I slightly "oversize" the furnance according the J-Sizing?
I know I posted alot of information here but I need some assistance. Any help would be greatly appreciated.