Question:
South Florida
2970 sq ft (600 sq ft is upstairs)
2-story
vaulted ceilings downstairs
2.5 ton cools upstairs, plus guest bedroom downstairs
need new a/c for downstairs
Two different Trane contractors have offered opinions
Trane 15i 3.5 ton
Trane 19i 4 ton (not available in 3.5 ton)
These units will have rebates available effective 3-1-06
Answer:
A manual J heat-gain heat-loss is an absolute requirement!
With Vaulted ceilings adjust supplies and Returns so the air is allowed
to stratify in the vaulted area as this saves a lot of conditioning.
Do NOT oversize the unit in a high or moderately high humidity climate
or most of the high SEER ratings will be lost!.
South Florida, summer outdoor design Key West 90-F dry bulb, 78-F wet
bulb around a 58% relative humidity
Miami 90-F dry bulb, 77-F wet bulb around a 54% relative humidity.
Tampa, 91-F dry bulb, 77-F wet bulb around a 53% relative humidity.
It is much more difficult to get 19 SEER than 15 SEER, the initial cost
should also be much less for the 15 SEER
You might only get around 15 SEER with the 19 SEER Condenser.
I am NOT there, but in general do what you can to reduce the heat-gain
and go with what the manual J calls for.
