Air flow, Variable speed, and manual dampers

[Max22]

I am currently evaluating 2 A/C contractors to install a new system and optimize it as best we can. Each has a different approach so I would really appreciate an objective take on a couple of things.
I live 5 miles from the coast in west central Florida. The house is about 2000 sq. ft. and 2 story. The 2nd story has always been much warmer but I always just attributed it to the fact that hot air rises.
The 1st contractor proposes a Trane 4 ton XR15 heat pump with a variable speed air handler, 15.0 seer. He says he will install manual dampers that will assist in getting more air upstairs.
The 2nd one proposes a Carrier 4 ton heat pump, 15 seer but without variable speed. When he looked at the job he said the 1st thing to correct is insufficient air flow since we only currently have enough space in the returns for 1000 CFM. He considers this crucial. He believes with sufficient air flow and proper balancing of the system the additional gains achieved with the variable speed are not worth the extra $$, unless we just have extra to spend, which we don't.
1st contractor says he will add air returns if possible and offers another option of taking the air from the garage instead.
Any thoughts on any of this are greatly appreciated.

[DanW13]

IMO you'd be better off with having dampers installed on all your supply runs and then have the contractor balance all the rooms so you have proper airflow to all the rooms. As for the one contractor wanting to take air form your garage space should know better, never never take fresh air or any other air from the garage space !! The contractor who suggest this should not even be considered IMO!!! Sounds like you need to have some duct work done to accommodate the 4 tons they are telling you your home needs, both on the supply and return.

[dash]

Warm air rises and cool air falls.

The heat gain/loss for upstairs and down will vary thru the seasons,manual dampers will need adjustng ,by the season/day.


Two systems or zoning is the best solution,for two stories.

Variable speed is what you need,along with the best controls,to dehumiddify indoor air ,here in steamy Florida.

Never take air from the garage!

[WhoIsThat?]

I'd get at least 4 more bids, then rank by contractor credibility [#1 gets 0.0] and whether the bid prices cluster together.

And if your median ZIPcode income is high
http://zipskinny.com/
they will probably push high-end units.

[sktn77a]

Unfortunately, when the BTU load upstairs and downstairs are significantly different and you only have a single system, you're going to need to send more cooling air upstairs in the summer and more heating air downstairs in the winter. You can do this with manual dampers or with an automatic zoning system.