In an older system it will be hard to determine what a new unit will do to
improve the cooling. Assuming that the freon pressure is correct, the filter
is new and clean and that the ducts and registers are clean, you can measure
the duty cycle to see how long the unit needs to run to bring the home from
temperature A to temperature B and also track the average running time per
day. Based on the units EER rating or by measuring the amperage draw of the
unit, you could then calculate your savings by using the ratings from a new
scroll compressor type of unit. This assumes that the new unit will run just
as long as the old one, which, if the old unit is pumping out cold air
properly, will probably be about the same.
If your unit is running well, I wouldn't replace before it dies. In the
meantime, you may get some improvement by making sure that the ducts are
properly attached to the registers and the return duct is properly attached
to the air handler. You don't want to be pulling hot humid air from the
attic into the system through any leaks in the return ducts.
: I recently moved into a home with an older central air conditioning
: unit here is Texas. I'm concerned about the operating costs of
: this older unit so I'd like to put something in place to measure and
: track the performance of the unit over time. However, I'm not sure
: what to measure and what metrics to calculate. Seems that duty cycle
: and supply/return duct temperature differences could be useful but I'd
: like to figure out how to get something like percent efficiency that I
: can track over time. Your help is appreciated!
: Sent via Deja.com