Access the compressor unit you plan to drain the refrigerant from and connect the liquid and vapor lines of the manifold gauge to the corresponding ports on the AC compressor unit.
Connect the input line from the manifold gauge to the input line connection on the Robinair 25150.
Connect an output line from the output jack on the Robinair 25150 to the storage container that will be used.
Open the Robinair 25150's recovery cylinder liquid port.
Set the machine's purge valve to the "recover" setting.
Plug the Robinair into an electrical socket and then press the power button to the "On" position.
Open the 25150's input port slowly and allow the machine to run until the refrigerant is drained.
Close the liquid port and shut off the gauges on the manifold gauge. Also close the input port and flip the power switch off.
Flip the 21150's recover valve to the "purge" position and restart the machine. Run until the vacuum is achieved.