I have a 3 ton air-conditioned that's 13 years old and I live in Florida,
it is a 10 sear split unit with a
electric heater in the airhandler mounted on the ceiling in the garage.
My question is this unit has cooled and heated the house well, is there any
reason for a new
heating /cooling load reading to be done before replacement of a new 12 sear
I realize that the brand name of the unit is not as important as the quality
It would not be a bad idea to have it recalculated. I think I would have
it done if you are not sure it was done before, however it is not likely to
have changed, UNLESS you have added insulation or made other changes.
The Manual J calculations are very precise, but ultimately it comes down to
a very unprecise choice of 3 tons versus 4 tons. It is always a big, rough
On the other hand, you may feel the old size cooled well, but you may not
be properly critical. I would spend, say, $100 if I knew I was getting a
I would demand that it be calculated. While Richard is correct that there
are only incremental sizes available, there is a 3 1/2 Ton unit in-between.
Your unit does more than control air temperature, thus the term air
conditioner vs. air cooler/heater. Any good company will change the unit
ONLY after running the calculation since your comfort and satisfaction with
the new unit should be a top priority.
If a load calculation showed that the unit was oversized which could be the
case with a unit that has cooled well, downsizing would have benefits. A
smaller unit would run longer pulling more humidity and costing less to
operate because of fewer starts. The higher efficiency units (above 12 seer)
are dual speed or variable speed compressors to provide for a almost
constant running of the unit. Where electricity rates are high the most
efficient unit while costing more to install, save more than enough in
energy to pay back the difference in a few seasons dependent mostly on the
rate per Kw. With a heat pump your savings could be even more dependent on
your heating requirements. Your local electric provider may be a source of
lots of information on the best options for your area. It is always a good
idea to confirm that equipment is properly sized and even more important
when increasing efficiency.
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