Unable to get A/C Compressor at Pressure..?

Question

This is a deep freezer compressor. The specs on the compressor say that they want R134a@95psi on the low side, but with standard auto R134a cans I am only able to get about 70psi, which does not chill enough. I am assuming this is because the standard auto cans are only 70psi? Also, what is the best way to get the compressor to 95psi?

Any help would be greatly appreciated! Thanks!!

Thanks for the response. Actually when I obtained it, it had a leak, which I fixed. I pulled a vacuum on it and then charged it, so I would really question if air contamination could be a problem, but I wouldnt mind some experts to give me some insight on this... :-)

Answer 1

Hello Tim:

Refrigerant has different pressures at different temperatures. Does your spec. sheet tell you what the high side should be? 95psig is rather high...at 95psig, the temperature of the refrigerant would be around 85 degrees. add 12 degrees of super heat, and the evaporator temperature would be nearly 97.

If you want your freezer to reach temp, the suction (low side) pressure will need to be around 9psig, not 95.

Did it tell you how much physical refrigerant is needed; e.g. "charge with 12 oz R134a?"

If the lines are contaminated with atmosphere, the pressure will be much higher (refer to Boyle's law). To test, let the pressure equalize in the high/low sides, then take a temperature. Find a pressure/temp chart for 134a, then see if you are close. If you have contaminates, it will be out of range quite a bit.

R134a is the same chemical composition, even if it comes from small 8oz automotive can, or a 30# refrigerator repair technician's canister.

Answer 2

at operating temp the suction pressure would roughly be 4-8 psi. Just weigh in the new charge and it should be fine.No need to guess. Remember to only charge as a liquid in the discharge side. Then once charged, turn it on and wait.

Answer 3

hey man ive used those on autos and had similar probs u might wanna try using an evac machine and then recharge