Trane CVGF-SVU02B-E4 Operation And Maintenance Manual page 72

High Lift Unloading Solenoid
The normally open contact of a CH530 control relay powers the normally closed high lift unloading valve
solenoid with the following logic:
LLID Relay High Lift Unloading
State Valve Solenoid
De-energized De-energized
Energized Energized
The high lift unloading valve
opens if the compressor is
running and the IGV position is
at or below the Trigger IGV% line
– 5%. The high lift unloading
valve closes when the IGV
position reaches the Trigger
IGV% + 5% or the compressor
shuts down.
Note that this 5% is of the full
IGV travel range of 100%. Also
note that operation of the high
lift unloading valve is
independent of the high lift
unloading limit mode as stated
below.
High Lift Unloading Limit Mode
For a Gear Drive chiller, the
minimum IGV position is 60% of
the Trigger IGV%. When the IGV
movement is being limited to the
60% of the Trigger IGV% point,
the high lift unloading limit
submode is displayed.
72
Machine Protection and
Adaptive
High Lift
Unloading Valve
Closed
Open
Compressor Start Up
At compressor startup, the
chiller is initialized as to not be
in high lift unloading. The rules
to enter high lift unloading mode
are as stated above. Also at
startup, sufficient time should be
allowed so that an accurate
Trigger IGV% may be calculated.
Here non-saturated conditions
exist right away resulting in
unstable temperature
measurements.
Manual Capacity Control
This is the Compressor Control
Signal mode override in
DynaView ™ . Here high lift
unloading solenoid valve
operation, 60% of the Trigger
IGV% and displaying of the high
lift unloading limit submode is
obeyed.
Function
No condenser gas bypass
Bypass condenser gas
Chiller Shutdown
The high lift unloading valve is
normally closed (de-energized).
There is no check performed to
ensure the valve is closed without
using TechView ™ .
CVGF-SVU02B-E4