Hermetic- Can be reciprocating, scroll and rotary compressor(s)
Semi-hermetic- Can be reciprocating, rotary or rotary screw, centrifugal
Open Drive- Can be reciprocating, centrifugal
Compression Ratio: How and why it is so important?
Our goal as mechanics is to achieve “the work” with the lowest compression ration
Compression ratio: Air Conditioning
Discharge pressure + 1 atmosphere (roughly 15 psi) 300+15=315
Suction pressure + 1 atmosphere 72+15=87
= Compression ratio =3.62 Comp Ratio
Compression ratio: Low Temp Refrigeration
Discharge pressure + 1 atmosphere 300+15=315
Suction pressure + 1 atmosphere 7+15=22
= Compression ratio =14.31 Comp ratio
Why is this important? It is a metric to use to see actual throughput of your work. If you are NOT using compression ratio’s as comparison of work, you should be. What other tools should you be using?
Always log your starting point:
Find the answer:
You have a low temp rack (R-22 with a C/I of 12psig and a C/O of 4 psig)
That rack is fitted with a 2-stage mechanical sub cooler and you are delivering 40 liquid temperature liquid to the 5-door frozen case. You have an expansion valve rated a 1 ton of capacitance, what is its corrected capacity?
Mechanical subcooling on a Package RTU?
Mechanical subcooling on a water-cooled chiller?
Mechanical subcooling on your home split system? HUH?