I'm about to get my central AC replaced and was hoping to get some
opinions on sizing. I currently have a 4-ton unit that feeds 13, 6"
round ducts (appx 1300CFM capacity). My house is very well insulated.
I recently recieved 3 estimates from authorized Trane dealers who
recommened the XL16i and XL15i models. My dilemma lies in determining
the correct size of the XL16 if I were to select it. All contractors
indicated that the 4-ton unit is a little large and that the existing
ductwork dosent support the CFM required for a 4-ton unit. None the
less, 2 of the 3 recommended 4-ton units. One of the 3 recommended a
3.5 ton XL15 or a 3.1 ton XL16 (likely because the 4 ton is not
eligable for the tax credit). I agree that a somewhat smaller unit (<4
tons) is appropriate because of the existing ductwork and the fact that
my existing system could use to run a little longer. Turns out that
the XL15 is available in .5 ton increments, while the XL16 is only
available in 1 ton increments. I'm inclined to go with the XL16i,
knowing that it will switch between 3 tons and 2 tons (70%) as
required, however I'm afraid that if it is slightly undersized it will
be spending most of it's time at 3 ton (losing the real 2-stage
advantage). If I go with the 4-ton, I have the same concern - that it
will may never run at the 4-ton level.
I suspect that the correct sizing is 3.5 tons given my discussions with
One more piece of info - all units will be matched to the appropriate
variable speed air handler.
Any comments or recommendations?
Thanks in advance,