What would the effects be if an r-22 system were to be evacuated and filled with R134a?
What is the reason that this equipment can not handle this gas?

The boiling points of the 2 are completely different.(-15 for 134 and -41 for R-22). In order for the system to maintain the correct temps/pressure, the refrigerant must be compatible. 134 A operates at higher pressure/temps than R-22 and will not cool, as the pressure in the system is directly related to temperature.

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Originally Posted by rickdb1

The boiling points of the 2 are completely different.(-15 for 134 and -41 for R-22). In order for the system to maintain the correct temps/pressure, the refrigerant must be compatible. 134 A operates at higher pressure/temps than R-22 and will not cool, as the pressure in the system is directly related to temperature.

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Very good answer but the kicker for me is the polyester oil used with the 134a its not compatible with the mineral oil used with r-22 systems.. turns it into sludge..

ISCEON 59
R417A Advantages
• The only HFC based R-22 replacement that is compatible with both synthetic and mineral oils (MO,AB,POE).
• Proven compatibility with all standard equipment components and materials used in R-22 manufactured systems.
• Suitable for use in scroll, screw, rotary and reciprocating compressors.
• Closely matches R-22's operational pressures.
• Can be used in a wide range of traditional R-22 temperature applications, and beyond, while providing adequate oil return and system capacity.
• Avoids the need for unnecessary oil changes and only requires minor system adjustments or modifications.
• Zero ODP (ozone depletion potential) HFC refrigerant.
• Improved COP (coefficient of performance), NU-22 has a lower global warming impact compared to R22, as indicated by NU-22's TEWI (total equivalent warming impact) measurement.
• Non-toxic and non-flammable (ASHRAE classification A1).
• Compatible with all standard refrigerant oils, NU-22 can drastically reduce the level of waste oil handling and disposal normally associated with using refrigerants requiring an oil change.
Performance Specs:
Boiling point
-41.8°C (-43.2°F)
Critical temperature
90.5°C (194.9°F)
Critical pressure
559 psia
Density (saturated vapor)
@ boiling point temp.
0.2447 lb/cf
Density liquid @ 25°C (77°F)
72.85 lb/cf
Heat of vaporization
@ boiling point temp.
89.42 BTU/lb
Quality Specs:
Max. moisture
0.001%vol
Max. non-condensable
1.5%vol
High boiling impurities
0.01%vol
Safety Specs:
ASHRAE designation
R417A
ASHRAE safety classification
A1
Max recommended exposure limits
1000 ppm
Refrigerant - NU22 (R417A)
Part
• Compatible with all standard refrigerant oils.
• ASHRAE Designated.
• R22 like operating characteristics.
• Exceptionally Low TEWI.
10% Energy Reduction Over R22.
• Zero Ozone Depletion.
• No Expensive Retrofits.
• Can Be Topped Off Repeatedly.
• ASHRAE Rated A1.
Non Toxic - Non Flammable

Can an R-134A AC unit be installed with a drained, flushed, and evacuated EXISTING R-22 evaporator coil?