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Posted by Bob Pietrangelo on June 23, 2007, 5:56 pm
> Several things occurred over the years.
>
> 1. Larger condenser's resulted in lowering the head pressure and raising
> the sub-cooling some. This allowed for less horsepower needed. An
> increase
> in sub-cooling gives better performance at the evaporator because of a
> better adiabatic exchange. [Less latent heat].
>
> 2. The advent of the scroll compressor has reduced the power requirements
> increasing the EER. The scroll has less moving parts and a scroll design
> that allowed less liquid / vapor refrigerant to flow over those parts.
> Less
> friction.
>
> 3. The return to TXV control has given the evaporators better performance
> [although many refrigeration tech's have always known that TXV's give
> better
> load / performance resulting in better superheat control. [Better
> superheat
> control gives the compressor less compression ratio's and less oil
> sludging
> from higher ratio's.] Also the use of "equalized port" gives better TXV
> performance, and the use of positive shut off valve [keeps the liquid in
> the
> condenser where it belongs on shut down.]
>
> 4. The increase of use for 2-speed compressors [staging is generally
> referred but not necessarily correct.] This allows for lower power draw
> during those days when air conditioning demand is relatively low.
>
> --
> Zyp
Zyp,
Great post! The only thing I question is the 2 stage compressors being a
true energy saver. I think they are more geared towards comfort issues than
anything else. They're savings over a 15-16 SEER singel stage system is
nominal during a cooling season, and their HSPF usually a little lower.
Your thoughts
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