1. The problem statement, all variables and given/known data To plot a TS diagram given the relevant data here http://imgur.com/Q9RNL8P for an air conditioning unit. 2. Relevant equations R134a is being used in an air conditioning unit, steam tables for -5hf 0hf and -5sf 0sf written below in exrapolation. 3. The attempt at a solution I've extrapolated the -2.7 to find the base pressure that goes into the evaporator from point 4 here http://imgur.com/zl4eIGJ And finally this is my plot from what I understand http://imgur.com/XE4HVtt I can see that point one is superheated so wouldn't I take the lower pressure as the -2.7degrees. But the pressure at -2.7 degrees is 2.7006 bar and the pressure of 5.2 degrees is 2.554 bar How is the warmer temperature a lower pressure? Am I right in setting the bottom pressure line at the -2.7 degrees? Thanks for reading I would appreciate any help with this.