Contamination Effects on the Performance of a Heat Pump Charged with R-407C and POE Lubricant

Abstract

The effects of contamination on the performance of a heat pump charged with R407c and POE were investigated. Testing consisted of three different phases of study. The first set of tests examined the long term reliability of a heat pump operating with an alternative refrigerant when the unit has mineral oil contamination present. One unit operated with R-22 and mineral oil, while the second used R-407c and POE with 11.9% mineral oil contamination. Data analysis showed that the R-407c unit operated at approximately 15 psi (103.4 kPa) higher pressure with compressor discharge temperatures which were approximately I O'F (5.6'C) lower than the R-22 unit. The capacity of each unit was approximately the same, yet the R-407c unit consumed more power during operation. The compressor from the R-407c unit showed normal wear for the length of time that the unit had been in operation. Although this was an encouraging result, the compressors had only completed approximately 20% of the cycles projected for the study. The next phase of the project involved performance testing of two additional heat pump units. Overall, the results showed that mineral oil contamination had minimal immediate effect on the performance of a heat pump. However, the power consumption during the high temperature heating and high temperature cooling tests increased by as much as 1822.5 Btuh (534 W) when mineral oil contamination of at least 5.6% was present in the first system, The final phase of the project examined the effects of water contamination on the reliability of a unit charged with R-407c and POE lubricant. One unit was left as dry as possible, while the second unit was contaminated with 1200 PPM of moisture. Laboratory tests showed little to no increase in moisture content as well as the three metals during the study. The total acid number in the water contaminated unit showed a general increase. This increase could have potentially lead to increased amounts of the trace metals as the acid attacked system components.