Around 2009, I bought a 1800 sqft Cape built in 1954.  Been 
renovating it myself.  This is our first home, and previous to 
installing AC, I had never lived in a home with AC.  We live on the 
border of CT and NY....sort of a NYC suburb.
If you are not familiar with it there is a site called costhelper...gives 
general estimates on costs of different things.  
http://home.costhelper.com/central-a...ditioning.html
In the Fall of 2011 we had both the furnace replaced and an AC 
system installed. Our home had forced hot air, so the ductwork was 
already in place. We got 3 quotes....ranging from 10-12k.  We went 
with the high end. I picked theropride for the hardware. 
what was included.
1. new furnace
2. new 1.5 ton compressor and airhandler
3. switch to a 2 zone system with the fabrication of a new main 
trunk and a new return trunk.
each of the 3 above broke down the price to into thirds...so each 
was roughly quoted as 4k.
So, this is the deal.  After the job was done, I had some problems. I 
could not keep my second floor cool enough.  On super hot days 
over 95 or 100, the ac would run non stop an the second floor 
would continue to get hotter and hotter.  I had the Hvac company 
come and they said there was nothing they could do and had 
excuses....or said well Capes are like that.  On four occasions my 
coil in the air handler froze.  
Needles to say I was a little ripped. After two years of trying to get 
the HVAC company to work with me on a solution I gave up.  
So....now the good news.  I solved the problem myself, and without 
spending a dime.
My cape had returns in every room on the first floor but none on 
the second floor. When the HVAC company did the install....they 
actually disabled all the returns on the first floor and and made one 
large return in the living room of the first floor. No change was 
made to the second floor...still no returns up there.
So, the saving grace was that I converted to a two zone system.  I 
thought about the problem I was having and changed my cooling 
strategy.  
For two years I set both the upstairs and downstairs to 
the same temperature, and I had problems cooling the upstairs. 
Both zones would be running all the time and the top floor was 
hotter than hell.
What I do now is...I set the downstairs 2 degrees warmer than the 
upstairs. It is magic.  Both zones are cool and the downstairs zone 
never turns on and is actually cooler than the upstairs.  What is 
happening is all the cool are is forced to the upstairs, and because 
cool air sinks and the return is on the first floor..... it cools the 
downstairs as well.  My system no longer runs all the time, no 
longer freezes, and the whole house is cool.
Feel free to pm me if you want to talk about it more. I can send 
you my phone number and we can talk about some of the specifics.