[Archived]

The
suction and discharge valves on open drive compressors serve two functions. The
first function is to open or close the charging port. The second function is to
open or close the refrigerant line. When the valve is back seated, turned all
the way counter clockwise the refrigerant line is open and the charging port is
closed. In order to see the system pressures, connect the gauges and turn the
valves clockwise until you see the pressures on the gauges. At this point, the
charging port and the refrigerant line are both open. If the compressor is to
be removed from the system, turn the valves clockwise until it stops. At this
point the refrigerant line is closed and the compressor may be removed with the
refrigerant maintained in the system. Note that you will still have refrigerant
pressure in the compressor that must be recovered or bled off.

Note
that the functions of both the discharge and suction valves are identical. The
discharge valve will always be the smaller of the two. Some systems have
pressure controls installed on the compressor side of the valves. Some systems
will have the pressure controls on the refrigerant line side. If your pressure
controls are on the refrigerant line side of the valve, no safety pressure
controls will prevent compressor operation if the valves are closed.

Refrigerant
may only be charged into the suction side of the system.

[Greg]

John,

Unless it has changed, somewhere in one of the Prevost manuals I read they stated you could introduce liquid refrigerant into the receiver. Being a confirmed chicken however I agree with adding refrigerant on the suction side, and for the home mechanics be certain you are introducing gas and not liquid.

[Archived]

I agree with charging at the receiver if the system has no
refrigerant and the compressor is not running. This would allow you to quickly
put perhaps half the charge into the system prior to starting the compressor.
Once the compressor is started the pressure in the receiver will almost exactly
match the compressor discharge pressure of 125 PSI or more. At this point the
pressure in the refrigerant drum will only be around 60 to 70 PSI depending on
ambient.

As Jon indicated, unless you do this on a regular basis, charging
into the suction line with refrigerant vapor is the only way to go.

[Charles]

Nope, don’t do it on a regular basis and don’t want to. I understand to introduce vapor only into the suction line the canister remains vertical. Thanks for the info, I think I’ve got it.