I own a 2300 sq ft house in SE Pennsylvania and am in the process of finishing my basement (~700 sq ft) with the plans to heat/cool the basement with my central forced air HVAC system. I currently have a 13 year-old builders grade Lennox 3T A/C unit and 75K BTU single stage furnace. Recently, my coolant pipes and coils froze up on my central A/C unit due to low refrigerant caused by a coil leak. Given the leak (2 lbs added this year, 1 lb added last year), the rebates, and with finishing my basement, I thought it was time to get a new A/C unit and furnace while I'm at it.
I've had three contractors provide estimates so far and I have a few questions for this forum:
1) Two of the three contractors performed load calcs. One recommended a 91K BTU Lennox G61V furnace and another recommended a 71K BTU Lennox G61V furnace. If I am going to add 2-3 new supplies to my ~700 sq ft basement would a 71K two-stage unit suffice? Conversely, would the 91K unit be overkill (see question 2)?
2) The contractor who recommended the 91K furnace also recommended a 4T A/C. My 75K furnace and 3T units have worked perfectly to date, so why would I want to upgrade the A/C - especially if I'm adding supplies to the basement (which will probably remain shut in the summer)?
3) The contractor who did not do a load calc is recommending Whirlpool. I have never heard of a Whirlpool furnace or A/C and was wondering if anyone can address the quality and reputation of Whirlpool HVAC systems? It is by far the least expensive of the three quotes.
Thank you in advance!