mike_home and others,
We are in hot, humid FL. Load calculation was done prior to us building several years ago. This model calls for a 3-ton. Neighbors with this model have 3-ton condenser, but they let us up it to 3-1/2 ton because we thought we were adding the lanai as usable space (not just the occasional dog house). By the way inside the garage the whatever it is called is a 4-ton currently.

We got different estimates and most everyone said to go with the 3-ton unit (because the replacement doesn't come in 1/2-ton sizes). The guy we are going with said this: he says go with the 4-ton. He said he has been getting lots of complaints lately because the weather has been close to 100. People's a/c units are not doing too well because it is so overly hot. The guy we are going with said that the unit we selected is a two stage (or 2 speed, if you will). It will run most of the time on the lower speed as a 2.? ton unit. But when it is really hot, it will run as a 4-ton unit. He said if we were going with a one stage (1 speed) a/c, then 3-ton would be okay. What do you think?

Let's review what you stated:

The original load calculation for the house was 3 tons, but the builder allowed you to pay to oversize it. Builders are happy to take money for upgrades whether it makes sense or not. That extra room you were going to add would not have made a significant impact on the load calculation.

All the neighbors with the same model have a 3 ton unit. Do you ever hear them complain their AC can't keep the house at 75 degrees on the hot summer days?

You other estimates have specified a 3 ton. They can easily sell you a bigger condenser and make more money, but they are choosing not to do this.

You live in Florida which suffers from high humidity. This is the primary reason you should not be over sizing the condenser. You want the indoor humidity to be 40-45%. If you over size you will never achieve this level.

The statement that really bothers me is that he is telling you that if you buy a single stage then you should get a 3 ton size. His logic about the 2-stage sizing is wrong in my opinion.

The primary reason for spending money on a 2-stage AC is for improved comfort. If you get the 4 ton you are wasting your money. You might as well buy a 3 ton single stage.

If you really want this questioned answered then have a load calculation done. A reputable contractor should do this as part of his quote.

This goes for everyone; do your own load-calc; have others help you.

http://www.loadcalc.net/

After you have the calc done right, click on the SIZING link & see what U can do with it. We can help U with that...

After working on my hvac system and reading hvac fourms, I discovered that Trane is only sold by big hvac dealers. One gets the best deals from smaller hvac dealers. ICP, Goodman, and ever Carrier are available from them. They all have Copeland compressors.

What is the definition of a big dealer? If Trane does require an HVAC dealer to be some minimum size (I don't understand why they would do this), then look for an American Standard dealer which sells the same equipment as Trane.

When one looks at the yellow pages, the Trane dealer is the largest in town. Check out this for price and tonnage. You will be shocked on the markup. http://www.acdirect.com/ac-package-unit-learning-center-ac-sizing-calculator. They also are in S. Florida.

for above poster...your remarks are getting off topic and not considered good forum etiquette. If you want to discuss brands, quality, pricing, then start your own thread rather than hijacking another.

TD

He asked a question and I answered it.

three ton. the last thing you need in a hot humid climate
is an oversized hvac system.
going up in tons means ducts are undersized.

oversizing means less run time, less dehumidification
& high indoor relative humidity. plus added equip
costs upfront & higher operating costs long term.

I'm very comfortable with my 15 SEER heat pump.
single stage condensing unit, variable speed
air handler. handles RH with no issues except
for seasons with low cooling loads, then RH creeps
from 52% to 54-56%. I have a whole house dehumidifier
that I hardly ever use...because I have little need for
it because I've tightened the house leakage, put ducts
inside conditioned space & sized both hvac system
& ducts for the system I designed.

two stage IMO is cya for hvac co's who don't want
to be called out to your house on the 10 days a year
temps pass the norm.
put in a system that can dehumidify, and keep it simple.
again IMO.

best of luck

Good advice above!