Bell, The pressures are listed on the bottom of the page I posted a link to:
"Pressures on gauges...
The readings on gauges are in pressure psi. If you look at the inside of the gauge there is a pressure temprature chart printed on the gauges for r-12, r-22, r-502. High and low side. Newer gauges have different charts.
Lets look at a few examples.
R-12 on the gauge.
If the pressure on an r-12 system on the low side, while the unit is running is 35 psi.(the outer black colored chart) then look at the smaller circles for the R-12 circle. The needle pointing to 35 psi. also crosses the R-12 circle, look at the corresponding number on it to determine what temperature the coil is operating at. It will be about 38 degrees F'.
If your hi side on r-12 is at 160 psi. then look on the inner part of the gauge on the high side it will read about 120 degrees f.
Lets look at r-22 on the gauge.
If you have a low side of 68 psi. reading on your gauge then look at the inner chart for r-22 at 68 psi. it is about 38 degrees f.
If you have a high side reading at 220 psi. then on your chart the gauge will read about 110 degrees f.
The evaporator (cold coil) on any air conditioning system should never be below 32 degrees f. Why because the condensate (water) on the coil will freeze, freezing up the system.
Freezers and refrigerators keep the temperature of the evaporator (cold coil) below freezing to keep the freezer cold enough to freeze. The coil operates at about 0 degrees f. So with the coil being that cold the condensate will turn to ice which will clog up the coil with ice. This will shut down the cooling. Refrigeraters have a defrost timer that turns on the heaters and shuts off the compressor. The timer keeps the defrost on for about 30-40 minutes. The thawing ice will drain down to the water pan under the frig to evaporate.
If your system runs low on refrigerant it will freeze up because the lack of pressure means the evaporator (cold coil) will be under the 32 degree mark, thus freezing the water.
It seems weird that if you loose refrigerant you would think that the system would warm up but thats not how it works. Think about it.
FOR THE R-134 PRESSURE CHART CLICK HERE>
http://members.tripod.com/~jbabs714/chart.htm"
Found this too:
