Can I Pull Refrigerant Into Compressor By Closing Low Side Service Valve?

I have put on gauges and turned unit on. I closed service valve on low pressure side and the pressure increased on low side but never went down to a vacuum.
asked 6 years ago in Climate Control by anonymous
2 Answers
Closing the low side valve and leaving the high side valve open while the unit is running would indeed give you this result. The reason being is that the pressures being read when a valve is closed, is the pressure upstream of the valve, towards the evaporator. In this scenario, the low side valve is closed and high side open, mass flow is zero, however pressures across high side and low side are equalizing, which is what you’re witnessing.
answered 5 years ago by AC Expert (660 points)
What AC Expert said is correct, but I think he missed the point of the question. Pulling a system into a vacuum is done with a vacuum pump and you wouldn't close either line to accomplish this, but just hook up the pump and pull it down to 500 microns or less. Once I hit 500 microns I let the pump run for 45 mins to pull a good vacuum.

If you are actually trying to pump the freon into the compressor which is what it sounds like Consider what each line is actually doing. Freon is being sucked through the suction line (bigger line) and then compressed and pushed through the liquid line (small line). So to pump the freon into the compressor, close your high side king valve, which is the liquid line or small line, and then push the contactor in. You should see your suction line guage start to move down. The suction line king valve usually take much longer to close, so when I do use it, I acutally close the suction line and then back it off so it can pull down that way once I hit 10 psi I can close it off completely and I'm done. Attach you recovery machine, recover the minor freon left in the system and then you are ready to work on the lineset or indoor coil.
answered 5 years ago by fixmyair (340 points)
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