Zone dampers

[asihi]

I have a question that I was hoping to get some help with. I live in a 4 bedroom Ranch that's approximately 3000sf and is 14 years old.
We are remodeling our basment and are upgrading our HVAC system.
The basement is going to be used extensively so we want it to be as comfortable as possible.
The HVAC tech recommends installing a new 125,000 furnace and 4 1/2 ton AC unit for the main floor of the building. For the basement, he wants to add a 75,000 btu unit and a 2 ton AC unit.
I was talking to a friend of mine (not in the HVAC trade) that said this may be a little bit of overkill.
He mentioned something about zone dampers, where each floor would have its own control to operate a single furnace and AC unit independently.
I know very little about this and was wondering on what your thoughts would be. Would zone dampers work? Thanks in advance for your help.

[beenthere]

Get estimates from other companies. You need a load calc done.
Unless you in an area with temps at -30 in the winter. And have a lot of windows, your current guy is grossly over sizing.
Plus, they don't make a 4.5 ton A/C.

If you over size, you could end up with high heating and cooling bills, and in teh summer with humidity that is too high and causes mode.

[accutrol]

beenthere is right, you should have a load calc done on your home. Each and every home is different.
Zoning is a wonderful process. Since you are upgrading and hopefully the entire basement is unfinished, you have the perfect opportunity to zone your home. By utilizing a single system, I would recommend a 5 ton unit for your home. There are 2 ways you can zone the basement. #1- install zone dampers in every run in the existing duct system, with a zone control and thermostats on the first floor and the basement. Make sure that a bypass damper is also installed between the supply and return ductwork to relieve excess air pressure in the duct system, which could cause major problems.
#2 - take out the existing ductwork, install new ductwork for the first floor and new seperate ductwork for the basement. Each duct would have it's own single damper with the same zone control and thermostats. Again the bypass damper is crucial.
I have zoned several homes, and they all work very efficiently. And I have installed both configurations of dampers.

[sneezer]

Just so I have it clearly, you are suggesting multiple zones rather than just two dividing upstairs from the basement, correct?

[dash]

I'd go with zoning and a two stage furnace and two stage A/C.

With two stages ,when onkly one zone has a call(need to heat/cool),it will run on low stage,so there's less air to bypass.

Could go with Carrier Infinity Zoning and not need a bypass at all.