Hi I’m new in the business and trying to learn as much as I can and looking to get some help from you guys. I’m having a problem with my own A/C unit and can’t figure out what’s going on with it. Here is the situation:
I’m getting a very low Delta T, around 6 degrees difference… 73 degree return air and 67 on supply. I put my gauges on and got 20 psig on the low side and 157 on the high side. The indoor temp was 75. The outdoor temp was about 80 to 85. The suction line temp at the condenser was 77. I checked the air filter, evaporator coil and condenser coil to make sure there was no blockage. I then felt the evaporator coil and found that it was cold only about 40%. It has a fixed metering device/cap tube. Being the rookie that I am, I decided that the evaporator was starved and to add some refrigerant (yes I do have my CFC) about 2 pounds. I fully expected the gauge pressures to rise and the suction line temperate to drop and I was ultimately hoping to get a 10 degree superheat based on my A/C charging calculator.
After adding refrigerant the low side gauge rose to around 38 psig and the suction line temperature lowered only to 70 degrees. In my mind this equates to about 15 degrees saturation temperate and about 55 degree superheat. After realizing that adding refrigerant was not solving the problem, I put my tools away for the day and decided to think on it. Today I hooked up the gauges again and found that I’ve got 100 psig low side and 175 psig high side. The suction line temp was 70. I’m pretty confused about the change in pressure. I checked the evaporator coil and it’s still running only about 40% cool.
I appreciate any feedback.