High Discharge Temperature Control
If the discharge tempe rature increases abo ve 160 F (71.1 C) (PSIO Software Version 09 an d
higher) or 180 F (82 C) (PSIO Software Version 08 or lower), the guide vanes are proportionally
opened to increa se gas flow through t he compressor. If the leaving chilled water temperatur e is
then brought 5° F (2.8° C) bel ow the control set point t em pe rature, the controls will bring the
machine into the recycle mode.
Oil Sump Temperature Control
The oil sump temperature control is regulated by the PIC which uses the oil heater relay
when the machine is shut do wn.
As part of the pre-start checks executed by the controls, oil sump temp erature is compare d
against evaporator ref rigerant temperatur e. If the difference betwe en t hese 2 temperatures is
50 F (27.8 C) or less, the sta r t-u p will be delayed until the oil temperature is 50 F (27.8 C) or
more. Once this tempera ture is confirmed, the star t -up continues.

PSIO Software Version 08 and Lower

The oil heater relay is ene rgized whenever the chille r compressor is off, and t he oi l sump
temperature is less than 140 F (60 C) or sump temperat ur e is le ss than the cooler refrige rant
temperature plus 60° F (33. 3° C). The heater is then turn ed off when the oil sump temp er at ure
is: 1) more th an 160 F (71.1 C); or 2) the sump temperature is more than 145 F (62.8 C ) and
more than the c ooler refrigera nt temperature p lus 65° F (36. 1° C). The heat er is always off
during start-up or wh en t he compressor is runnin g.