During the machine start -up, the PIC will energiz e t he oil pump and provide 15 s ec on ds of
prelubrication to t he be arings after the oil pre s s ur e is v er i fied and before the cont rols start the
compressor. During shutdown, the oil pump will run for 60 seconds after the compressor
actually shuts down fo r the purpose of post-lub r ic at ion. The oil pump can als o be en ergized for
testing purposes in cont rols test.
Ramp loading can slow the rate of guide vane opening t o minimize oil foaming at st art-up. If
the guide vanes open quickly, the s udden drop in s uction pressure c an cause any refrig erant in
the oil to flash. The resu lt ing oil foam cannot be pum ped efficiently; oil pres s ur e falls off, and
lubrication is poor. I f oi l pressure falls below 15 ps i ( 90 kPa) differential, the PIC will shut down
the compressor.
Oil reclaim is accomplished by returning the system oil through the check valve/orifice (Item
11). As oil builds up behind the second stage impelle r, it is drained by the chec k v alv e /orifice
back into the oil reserv oir . An oil/refrigerant mi x tu re is drawn up from the oper at ing level of the
cooler into the guide vane housing. This assists the oil return system at low load operating
conditions.
Click here for Figur e 5 — Hermetic Compressor Lu brication System (EX Compressor Shown)