What makes efficiency?
The equipment manufacturers all have different lines of equipment that have different efficiencies. The least efficient being 13 SEER and the most efficient being over 20.
My question is "What changes are made to improve efficiency in a design?"
I see that the more efficient Trane systems have a much larger condenser, so the size of the coil might be part of the answer.
What makes an efficient design?
Giant outdoor coil. Giant indoor coil. Compressor. 2 stage/ or 2 compressors. Smaller HP condenser fan motor, or a VS condensre fan motor. Line set size requirement.
Requirement of a VS blower.
What 'beenthere' stated, along with some added opinions.
Beenthere: "2 stage/ or 2 compressors. Smaller HP condenser fan motor, or a VS condenser fan motor, and a 'Requirement' of a VS air handler blower."
It appears the design-engineers' idea is to do more with larger coils while using smaller more efficient motors.
However, it appears that the laws of physics cannot be violated or avoided.
Back in the mid-1970's when I got into HVAC Tech work some of the compressors had higher Btu/hr ratings than the Rating of the matched condenser & evaporator coil.
Under higher load conditions those compressor's would pull a lower pressure & temperature; a much colder evaporator.
When the higher loads, any combination of latent & sensible heat, boils off the liquid refrigerant in the E-Coil faster than the compressor can handle it, the pressure & temperature rises.
If my memory is accurate, some 2-ton condenser's has +26,000 & 27,000-BTUH compressors. They could handle a big heatload increase in the rate of evaporation boil off & keep the pressure & temperature within reasonable dehumidification perimeters.
Of course, that higher pressure increases, to some degree, the volumetric capacity of the smaller capacity compressor, however, the pressure/temperature of the E-Coil could be above the dew-point of the air going through it.
Well, when you get all the new engineering 'beenthere' mentioned, the new equipment does a fantastic job.
Add to the above by 'beenthere,' a digital adjustable half degree increments differential up to 3 or 4 degrees from the t-stat setpoint, which would reduce the number of cycles & the SEER Rating will once again improve. EER is another story... - udarrell