Help with upgrading system

[southern_boy]

Hi all,
I have been checking out this forum for several weeks now seeking knowledge and have been amazed!

Seems I have been in the building industry for over 20 years and I have looked the other way when it come to HVAC and really never had an understanding of how many variables are involved . I have always had a company or individual I could trust until now.

My mother really wants to upgrade her old 10 seer equipment with some much more efficient units like 15 or more. This has turned into a headache as I have been trying to help her She has quotes from several companies but everyone has a different price/opinion. But I do know I want it to be right or in my mind it's not even worth doing! So, I am reaching out to you guys to help me feel in the blanks. Here are all the details on house and existing units.

2 story slab house 21 years old, One furnace in garage (utility room) and one in center of house in furnace room/closet currently 2 units on first floor 2 & 2 1/2 ton and 3 for the second floor 80 percent lp funaces/10 seer ac units. The 2 1/2 serves the kitchen, breakfast, hall, pantry, 1/2 bath, laundry, foyer (which is open to 2 story), and living room (which is open to the 2 story as well). The 2ton serves the master bedroom, M/bath, 2 secondary bedrooms, hall bath and hallway. The 3 ton serves an upstairs office, bathroom, bedroom, foyer, and living room. It also includes a huge bonus room over the garage (18' x 40"). The thing about the house is how chopped up it is as all the rooms upstairs have several knee walls in them that back up yo attic due to the 14/12 roof. She has been having a humidity problem in which I feel in due to air circulation (mildew and mold forming). First floor ceilings are 9' with a drop down ceiling for the ductwork for the 2 units on the first floor through the center of the house. I know its straight pipe not sealed in the cavity. 2 1/2 ton unit has only 2 returns foyer and living room (dropped out of ceiling through plenums in walls). 2 ton has 3 returns, one in master bedroom, one in secondary bedroom and one in hallway right outside closet.

Now, here are my issues.... There has been 3 different companies look at this upgrade. 2 looked at the current units, sized tons to the current ones and offered 15 seer units & priced Trane and Lennox Air handlers and heat pumps and said "we will make it right if it needs anything else. The third pushed goodman communicating hybrid systems 2, 3, 3 tons 16 seer and said up sizing was not a big deal with those systems.

Ok, after all this I need a beer, lol joking sorta... It did drive me to do the load calculations using HVAC calc. Here they are!

First Floor Zone 1 (Current 2 1/2 ton)
Sensible Gain 22,652
Latent Gain 4,231
Total Heat Gain 26,883
Total Heat Loss 43,483

Fist Floor Zone 2 (Current 2 ton)
Same order as above
14,661
2,132
16,793
22,884

Second Floor (Current 3 ton)
22,432
1,012
23,444 (really not sure why lower tham above zone 1)
27,251

Any help or advice would be grateful and much thanks in advance!

[southern_boy]

Seems I was a little tired when I posted this last night. Maybe this will help make sense of my questions!

All 3 companies looked at only the current units and sized everything to them. The lennox and trane companies sized everything existing exact and in a 15 seer. The goodman guy rounded up the current 2 1/2 to a 3 and sized the other 2 the same as the existing. He was also pushing hybrid communicating systems to help with the humidity but said goodman did not make 1/2 ton sizes in their high efficiency equipment

I was not sure I had faith in anyone so far and decided I should do the load calculations using HVAC calc. It seems like to me from report it really needs a 2.5 1st floor zone 1, 1.5 first floor zone 2 and a 2 ton upstairs? The upstairs is really big with the bonus room at 18' x 40' 1,358 sq' (which includes other small rooms attached to it as well) and the open foyer/living room coverage as well. Why do the numbers lead me to think I need a ton smaller of a unit upstairs?