Question about Heating & Cooling
Hi, this depends on the outdoor air temperature and type of freon this unit has. The hotter it is outdoors, the higher the pressure will be as they use a pressure/temperature relationship. If the unit is R-22 and lets say it is 90* F. out side, the low side or suction side will be at around 68 to 72 p.s.i which would give you an evaporator temperature of 40* F. Head pressure would be at around 90* plus 27*= 245p.s.i. This is if the condenser fan is in good condition and the outdoor coil is clean. If you are using a set of manifold gauges you have the pressure/temperature scale right on it. If the unit has a TXV for metering, you would need to charge it using the subcooling method. On a Non-TXV you would use the superheat method. If you are using the new R-410a freon, the pressure are extremely high in these systems compared to the R-22 system, so make sure you look at the units data plate to read the type of freon. The color of the container is green for R-22 and a Pink for R-410a and the 410 a unit will display a pink warning sticker on the unit to tell you. The pressures on the R-410 would be at 90* F, low or suction side at that temp is around 125 p.s.i., and around 400 to 420 p.s.i. on the high side, much higher then the R-22. You would also need a manifold gauge set made just for the R-410a (AZ-20) as of the extreme pressures in the system. There is never a set pressure to go by as the outdoor temperature will raise and lower the pressure of freon very fast. If you are asking this question because you have a manifold set and are taking a reading, the unit has a charging method pasted right on it from the factory showing what pressure they want it to run at. Your gauges also can be used as a pressure temperature chart, or you can pick one up free of cost at a a/c parts house to keep with you. It will show you how to calculate the charge for your unit. If you are familar with pressures, this should be of a great help to you. I hope that I have helped you on getting the unit charged properly. Please keep me in mind when rating me, as I know you will be kind. Just drop by a wholesale a/c parts house, walk in and ask for a pressure temperature chart, and they will hand you a couple of them. They have very good information and no how on all of the most common freons in use today.
Best of luck
A/C, Heating, & Refrigeration Contractor
Posted on Jul 30, 2010
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Posted on Jan 02, 2017
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