PSIO Software Version 09 and Higher

The oil heater relay is ene rgized whenever the chi lle r compressor is off and the oil sump
temperature is less than 150 F (65.6 C) or the oil sump te mperature is less than the cooler
refrigerant tempera ture plus 70° F (39° C). The oil heater is turned off whe n the oil sump
temperature is eithe r 1) mo r e th an 160 F (71.1 C); or 2) the oil s um p t emperature is more tha n
155 F (68.3 C) and more than the cooler refrigerant temp erature plus 75° F (41. 6° C). The oil
heater is always off duri ng start-up or when the comp ressor is running.
When a power failure to th e P S IO m odu le has occurred for more t han 3 hours (i.e., initial
start-up), the oil sump is heated to 100° F (56° C) abo ve the evaporator refrigerant temp erature
or 190 F (88 C), whichever is lowe r. Once this temperat ure is reached, the oil pump will be
energized for 1 to 2 minute s or unt il the oil sump temperatu r e c ool s to below 145 F (63 C). The
normal heating algori thm is now followed once ra m p loa ding has been completed .
After a 3-hour power fail ure, the oil temperatur e m us t rise to the higher oil tem per a ture. The
controls will delay the start of the compressor unt il this temperature is met .
Oil Cooler
The oil must be cooled whe n th e compressor is running. Th is is accomplished throu gh a
small, plate-type he at exchanger located be hin d the oil pump. The heat exch anger uses liquid
condenser refrigerant as the cooling liquid. A refrigerant t hermal expansion valve (TXV)
regulates refrigeran t flow to control oil tempe rature entering the bear ings. There is always a flo w