alert threshold (18 psid [124 kPa]). Once runnin g, the auxiliary oil pump will remain on until the
compressor is turned off and will deenergize with the m ai n oil pump after the post- lu be time
period.
Shaft Seal Oil Control (Open Drive Machines Only)
All open drive machines r equ ire that the shaft seal be bat hed in oil at all times, especi ally
when the machin e is not running. This ensures th at refrigerant doe s not leak past t he seal. The
PIC control will energize the oil pump for one minute if t he oil pump has no t operated during the
past 12 hours.
It is important to note tha t if control power is to be turn ed off for longer than this per i od, the
refrigerant charge m us t be pumped over into the utili ty vessel. Because the oil he ater will also
be off during this time, stor i ng the refrigerant wi ll al so prevent refrigera nt migration into the oil.
Ramp Loading Control
The ramp loading cont rol slows down the rate at which the compressor l oads up. This contro l
can prevent the compre s s or fro m loading up during the sho rt period of time when the mach ine
is started, and the chille d water loop has to be broug ht down to normal design condi tions. This
helps reduce electrical demand charges by slowl y bringing the chilled water t o control point .
However, the total pow er dr aw during this period rema ins al most unchanged.