Parker PSD04 - 6.9 Superheat control algorithm

Parker RAC Europe PSD04 | User manual ver. 3.6 | Code 144PSDI364
Page 24 of 74
6.8 Debugging mode
The debugger feature is enabled when Pr02 = 2: the valve will move from a Debug minimum position (parameter Prd1)
to a Debug maximum position (parameter Prd2) with the step rate defined by Debug step rate (parameter Prd0).
Internally, the actuated step rate value is clamped to the maximum step rate of the selected valve.
6.9 Superheat control algorithm
The purpose of this control is to maintain the Superheat (SH) at its set-point value, in order to maximise the efficiency
of the system and ensure that the compressor is protected by entrance of liquid. The SH is usually controlled by a PID.
Setting the Main control type (Pcty) selects the SH-algorithm to enable:
• Pcty = 6 : EVCO algorithm
After selecting the control algorithm, it is necessary to set the various regulation parameters:
• SH set-point (Pc01, Pp01)
• LoSH set-point (Pc02, Pp02)
• HiSH set-point (Pc03, Pp03)
• LOP temperature (Pc04, Pp04)
• MOP temperature (Pc05, Pp05)
• EVCO algorithm:
 PID proportional band (Pc13, Pp13)
 PID integral time (Pc14, Pp14)
 PID derivative time (Pc15, Pp15)
 Start-up delay (Pc20, Pp20)
 Start-up position (Pc21, Pp21)
 Fast action (Fast)
 Neutral zone high threshold (PNHi)
 Smart band zone threshold (Pcz)
 SH filter time constant (SHFi)
 Fast action threshold (FaTh)
SH parameters set selection (SetP) supports selection of one of two different sets of regulation parameters. Each set
includes SH set-point, PID parameters, and LoSH, HiSH, MOP and LOP alarm set points, start up opening position and
delay. Example uses are: using set1 parameters for a chiller, set2 for a heat pump.
SH parameters set selection (SetP) supports switching from one control parameter set to another simply and quickly.
It is possible to change the regulation parameter sets directly by modifying SH parameters set selection (SetP), if a
serial interface is present, or via correctly configured digital inputs on the standalone version. If one of the digital
inputs (DI1 or DI2 or DIHV) is configured as "Change SetP" (DI1 function (Ph11) or DI2 function (Ph21) or DIHV
function (Ph31) setting to 2), the parameter sets for the PID control are determined by the digital input status: set 1 is
selected if the input is low, set 2 is selected if the input is high. If no DI is configured for parameter set modification,
the data is taken directly from SH parameters set selection (SetP).
Position
100%
0%
t [s]
Step Rate = Prd0 step/s
Prd2%
P
r
d1%