Refrigeration Compression Ratio
Absolute compression ratio from suction and discharge pressures, with a high-ratio flag.
Example
You enter
- Suction pressure (psig) 70
- Discharge pressure (psig) 260
- Atmospheric pressure (psia) 14.696
You get
- Absolute pressures 84.696
- Discharge (psia) 274.696
- Compression ratio 3.2433
Checked against published worked examples from: ASHRAE Handbook Refrigeration (by name).
Details, formula, and sources
ScopeAbsolute compression ratio from suction and discharge gauge pressures (with altitude correction) and a high-ratio flag for single-stage limits (ASHRAE).
Formula or tableCompression ratio = absolute discharge / absolute suction = (discharge_psig + atmospheric) / (suction_psig + atmospheric); high-ratio flag above about 10:1.
Source and editionRefrigeration compression ratio = absolute discharge pressure / absolute suction pressure - per the ASHRAE Handbook Refrigeration compressor-performance fundamentals, by name; first-principles.
Free accessFirst-principles absolute-pressure ratio. Use the site atmospheric pressure at altitude, not 14.7, for accuracy. The compressor manufacturer's operating envelope governs.
What governsEstimate. AHJ and licensed mechanical contractor govern. ACCA Manual J / D / S supersede rules of thumb.
API field namessuction_psig, discharge_psig, atmospheric_psia, suction_psia, discharge_psia, compression_ratio
- Atmospheric pressure 14.696 psia at sea level default; user-adjustable for altitudesite barometric pressure