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VSG/VSSG • Installation, Operation and Maintenance Manual •Vilter/Emerson • 35391STG
Section 4 • Operation
Oil Temperature Control Valve (Oil
Mixing Valve) Operation
INITIAL POSITION
The temperature control valve is in the closed position
when initially installed.
With the temperature control valve de-energized, the
valve is set to its initial position. The temperature con-
trol valve will be in the closed position with the actuator
indicator displaying CLOSED.
When the temperature control valve is energized, the
valve will rotate to fully OPEN.
OPERATION
With the compressor not running, when electrically en-
ergized, the PLC will turn the temperature control valve
to fully open (100%).
When the compressor starts, the valve remains fully
open (100%) until the oil injection temperature rises
above the control setpoint. When the oil injection tem-
perature rises above the control setpoint, the oil temper-
ature control valve will begin to close. The hot oil from
the oil separator begins to divert to the oil cooler, mix-
ing the hot and cooled oil
fl
ow streams together down-
stream of the oil temperature control valve. The valve
can fully close (0%) diverting the entire oil
fl
ow stream
to the oil cooler.
As the oil injection temperature drops below the set-
point, the oil temperature control valve begins to open
so that the oil injection temperature does not become
too cold.
When the compressor stops, the valve returns to fully
open (100%).
Figure 4-6. Oil Temperature Control Valve (Oil Mixing Valve)
FAIL POSITION
• The temperature control valve remains in the last po-
sition when power is removed.
SCREEN DISPLAY
• The oil temperature control valve, identi
fi
ed as “OIL
MIX” on the main PLC display screen, shows a numer-
ical value with “%” as units. This is to be understood
as “% OPEN.” It is a direct indication of the position of
the ball valve.
100% OPEN
• Oil
fl
ow stream is entirely bypassing the oil cooler.
99% to 1% OPEN
• Oil
fl
ow stream is partially bypassing the oil cooler
and partially diverted to the oil cooler.
0% OPEN
• Oil
fl
ow stream is entirely diverted to the oil cooler.
MANUAL OVERRIDE
The actuator of the oil temperature control valve has a
handwheel that can be engaged to override the electri-
cally determined position of the ball valve.
1. Push handwheel down and rotate to engage inter-
nal slot with
fl
ats, see Figure 4-6.
NOTE
Actuator does not have mechanical stops. Do Not
rotate past open or close position. Use visual indicator
to position actuator.
2. Once engaged, push down handwheel a second
time to disengage gear train and rotate
CLOCKWISE
to
OPEN
or
COUNTER CLOCKWISE
to
CLOSE
.
3. To return actuator to normal operation,
fi
rst check
“% OPEN” on control panel. If value is 100%, return
actuator to OPEN position as shown on the visual
indicator. If value is 0%, return actuator to CLOSE
position as shown on the visual indicator.
Handwheel
Visual Indicator
Actuator
