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Subcritical Parameter
HPV Mode Setpoint
HPV Mode Hysteresis
HPV Subcool Setpoint
HPV RS-Temp
HPV PB-Temp (P)
HPV INC (I)
HPV DDER (D)
HPV Max Valve %
Table 6-2 - Subcritical Parameters
Outputs
Valve % Output
Table 6-3 - Outputs
6.1.2
HPV Transcritical Mode
(Normal)
In a booster Transcritical system, when the tempera-
ture exceeds a certain value, there is no longer an accurate
temperature to pressure relation. Because of this, the con-
trol temperature of T1 or T2 (defined by digital CTS), will
be the deciding factor of when the application will
switches modes from subcritical to transcritical. If the con-
trol temperature is above the HPV Mode setpoint, the
application will be in transcritical mode. Once the control
temperature is below the HPV Mode setpoint minus HPV
Mode Hysteresis, the system reverts to subcritical mode.
In transcritical mode, the application will stop main-
taining a subcool setpoint and start maintaining a setpoint
value from an equation to achieve a virtual subcooling
using only the pressure input as a control point. The con-
trol temperature (T1 or T2) will still be used to as a refer-
ence to calculate the setpoint equation. Below is an
24 • High Pressure CO2 Controller Installation and Operation Manual
Description
Setpoint for Subcritical and Transcritical mode
Control Temperature Hysteresis
Subcool Setpoint in Subcritical Mode
Subcritical proportional band offset
Subcritical proportional band
Integral sampling time
Derivative time
Maximum valve % opening
Description
Valve Percentage Output
estimation of what the setpoint will be for the given con-
trol temperature readings.
Default Value
31 DC
(87 DF)
3 DDC
(5 DDF)
2 DDC
(3 DDF)
0 DDC
16.7 DC
(30DF)
140 Sec
0 Sec
100%
Type
0-10VDC
Only or
LAN to
XEV20D
026-1731 Rev 0 01-DEC-2014
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