For the sake of argument and discussion, let’s use a perfectly matched, balanced, and calibrated R-410a home a/c system as an example.
Why do folks say it’s more efficient for said home a/c system to run continuously for 2 hours and then off for 5 minutes instead of cycling on/off much more often to achieve the same interior cooling setting on the thermostat? (I understand how home a/c system work, but I’d like to know why some say longer run times = greater efficiency.)
I’ve heard this claim time and again, but I’d like to know the science behind it. I live in Texas where a/c units run for hours during the day from June through September.
In: Engineering
If you look on the data plate of your outside unit (the condensor) you’ll see a rating for LRA and FLA. Locked Rotor Amps (LRA) is the current draw that would occur if the rotor shaft were instantaneously held stationary within a running motor (a stuck compressor). For a couple seconds, this amperage is present as the compressor motor overcomes the static pressure in the system. LRA is typically five to seven times the motor full load amps (FLA) which is the nominal amperage when the unit is up and running at proper pressures. So if your unit has a 5 amp FLA, it will have as much as a 35 LRA. Although that LRA state is very brief, it’s sucking power like crazy for those first couple of seconds. Multiply that by 5 times an hour and you have a hot, tired, inefficient system.
Latest Answers