Motor/Oil Refri geration Cooling C ycle
The motor is cooled by liquid refrigerant taken fro m the bottom of the conden s er v es s el
(Figure 4). Flow of ref r ig erant is maintained by t he pressure different ial that exists due to
compressor operation . After the refrigera nt flows past an isolatio n v alv e , an in-line filter, and a
sight glass/moisture indicator, the flow is split between motor cooling and oil cooling systems.
Flow to the motor flows thr oug h an orifice and into the m ot or. On models with a solen oid
valve, the valve will ope n if additional motor c ool ing is required. Once pas t the orifice, the
refrigerant is direc te d over the motor by a spray noz z le .
The refrigerant coll ec t s in the bottom of the motor casi ng and then is drained ba ck into the
cooler through th e motor refrigerant drain line. An orif ice in this line ma intains a higher pr essure
in the motor shell than in th e cooler/oil sump. The motor is protected by a tempe rature sensor
imbedded in the stator win dings. On models with a so len oid valve, higher motor t emperatures
(above 125 F [51 C]) en ergize the soleno id to provide additio nal motor cooling. On all models, a
further increase in temperature past the mo tor override set point will ove rride the temp erature
capacity control to hol d, and if the motor tempera ture rises 10° F (5.5° C) ab ove this set point,
will close the inlet guide vanes. If the temperatu re rises above the safety lim i t, the compressor
will shut down.
On machines with EX compres s o rs, the oil is also coole d by liq uid refrigerant. Re fri gerant
that flows to the oil cooling system is regulated by a thermostatic expansion valve. There is