Post implementation review R134a replaced with HyChill Minus 30

I am considering replacing the R134a refrigerant in my car aircon system with a hydrocarbon refrigerant. The candidate is Hychill Minus 30 (HC-30).

Comparison of R134a and HyChill Minus 30 gave a limited comparison of R134a and HC-30 from the point of view of pressure temperature behavior as it impact practical implementation and measurement.

This article is a post implementation report, and baseline for future system evaluation.

The vehicle uses a TXV and variable displacement compressor, so low side pressure should be controlled by the variable displacement compressor, and evaporator superheat controlled by the TXV.

The system was evacuated and charged with 240g of HC-30, being 30% of the R134a charge as advised by Hychill, and leak tested.

Fig 5

After settling, on the driveway with no supplemental air flow, fan on full, OAT 22°, on a digital manifold set for R134a, the low side pressure was 255kPa, evaporator outlet 12.9°, displayed superheat 7.2°. At this pressure, R134a calibration reads 2.0° high, so evaporator superheat is corrected to 5.2° which is quite within expectation for a TXV controlled expansion.

It is worth noting that on a hot day, evaporator superheat was measured with the original R134a charge at 16° which if we assume the TXV was not defective, indicates probable gross lack of refrigerant. The loss of refrigerant may just be low rate loss through hoses and shaft seal over 15 years… and it may still be leaking very very slowly.

Fig 3

The high side read 1015kPa, 40.6° at the service valve, and indicated subcooling of 2.6° which needs correction for HC-30 to 2.0°. Superheat is lower that expected, possibly due to less air flow that one would expect in motion, but possibly indicating that the charge is on the low side. More observation needed.

On a drive test it is working normally.