One of the very first steps when it comes to diagnosing your home air conditioner, refrigerator, or even your vehicle’s air conditioner is understanding the temperature and the current pressure that your system is operating at. Having these facts along with the saturation point, the subcool, and the superheat numbers for the refrigerant you are working on are essential when it comes to really understanding what is going wrong with your system.
After a visual inspection the very next step for the most seasoned technicians is pulling out their gauges and checking the pressure and temperature. It just becomes second nature after enough calls. I have heard stories of rookie techs calling some of the pros on their team for help on a system that they’re stuck on. It doesn’t matter what the situation is. It doesn’t matter if you’re in Miami or in Fargo. It will never fail that one of the first questions the pros ask the rookie is what is your subcool and what is your superheat? Having and understanding these numbers is key to figuring out what to do next.
But, these numbers won’t do you any good if you don’t know what refrigerant you are dealing with and what the refrigerant’s boiling point is at each pressure level. This article aims at providing you with just that information.
R-600a Applications
Isobutane is being seen more and more across the world. This holds especially true as various countries begin to phase out the ever common HFC refrigerants such as R-404A and R-134a. There will come a time where HFCs area thing of the past and we need to be ready for it. Today we are seeing isobutane based systems in home refrigerators/freezers, vending machines, ice machines, stand alone supermarket refrigerators/freezers, and many more expanding options. While they are quite popular in Europe and in Asia it is only a matter of time before they start showing up in United States. If you haven’t run into one of these systems yet then it’s only a matter of time.
For more information on R-600a please look at our R-600a Refrigerant Fact Sheet.
R-600a PT Chart
Let’s take a look at the pressure table for R-600a isobutane.
| °F | °C | psi | kpa |
| -40 | -40 | 4.16 | 28.7 |
| -36 | -38 | 4.6 | 31.75 |
| -33 | -36 | 5.08 | 35.05 |
| -29 | -34 | 5.6 | 38.62 |
| -26 | -32 | 6.16 | 42.47 |
| -22 | -30 | 6.76 | 46.62 |
| -18 | -28 | 7.41 | 51.09 |
| -15 | -26 | 8.11 | 55.9 |
| -11 | -24 | 8.85 | 61.05 |
| -8 | -22 | 9.66 | 66.57 |
| -4 | -20 | 10.51 | 72.48 |
| 0 | -18 | 11.43 | 78.79 |
| 3 | -16 | 12.4 | 85.52 |
| 7 | -14 | 13.45 | 92.7 |
| 10 | -12 | 14.55 | 100.33 |
| 14 | -10 | 15.73 | 108.45 |
| 18 | -8 | 16.98 | 117.07 |
| 21 | -6 | 18.31 | 126.21 |
| 25 | -4 | 19.71 | 135.89 |
| 28 | -2 | 21.19 | 146.13 |
| 32 | 0 | 22.77 | 156.96 |
| 36 | 2 | 24.42 | 168.39 |
| 39 | 4 | 26.17 | 180.45 |
| 43 | 6 | 28.02 | 193.16 |
| 46 | 8 | 29.96 | 206.54 |
| 50 | 10 | 32 | 220.61 |
| 54 | 12 | 34.14 | 235.41 |
| 57 | 14 | 36.4 | 250.94 |
| 61 | 16 | 38.76 | 267.24 |
| 64 | 18 | 41.24 | 284.32 |
| 68 | 20 | 43.83 | 302.22 |
| 72 | 22 | 46.55 | 320.95 |
| 75 | 24 | 49.39 | 340.54 |
| 79 | 26 | 52.36 | 361.02 |
| 82 | 28 | 55.46 | 382.4 |
| 86 | 30 | 58.7 | 404.72 |
| 90 | 32 | 62.08 | 428 |
| 93 | 34 | 65.6 | 452.26 |
| 97 | 36 | 69.26 | 477.53 |
| 100 | 38 | 73.08 | 503.84 |
| 104 | 40 | 77.05 | 531.21 |
| 108 | 42 | 81.17 | 559.66 |
| 111 | 44 | 85.46 | 589.23 |
| 115 | 46 | 89.92 | 619.95 |
| 118 | 48 | 94.54 | 651.82 |
| 122 | 50 | 99.34 | 684.9 |
| 126 | 52 | 104.31 | 719.19 |
| 129 | 54 | 109.47 | 754.74 |
| 133 | 56 | 114.81 | 791.56 |
Conclusion
There you have it folks. I hope this article was helpful and if you find that something is inaccurate here in my chart please do not hesitate to reach out to me. I have sourced this the best I could but there is always going to be conflicting data. I’ve seen it multiple times on various refrigerants. I’ll search for a refrigerant’s pressure chart and get various results all showing different pounds per square inch temperatures.