PPI Zenex Plus, User Manual, Page: 17 / 27

15
Zenex Plus User Manual
The zone at and above the boundary SP ( ) is referred as Heat Pre-dominant zone and that below the boundary SP ) (
is referred as Cool Pre-dominant zone. The controller automatically switches between the two zones depending upon the
Temperature SP. If the Temperature SP is below boundary SP, Cool Pre-dominant zone is active and the compressor is kept
ON. If the Temperature SP is at or above boundary SP, Heat Pre-dominant zone is active and the compressor is kept OFF. This
strategy eliminates the need for the user to manually switch the compressor ON or OFF.
I Control Zones “Dual”; separate tuning can be performed in the Cool and Heat Pre-dominant zones for f the parameter is set to
accurate control in each zone. The controller maintains separate sets of Proportional Band, Integral Time & Derivative Time
constants for each zone that are automatically selected and used by the controller depending upon the active zone.
However, if the parameter Control Zones is set to “Single”; the controller uses a single set of Proportional Band, Integral Time
& Derivative Time constants for both zones.
Figure 5.2
70°C
0°C
45°C
30°C
50°C
Temp. Control SP in
Cool Pre-dominant Zone
Temp. Control SP in
Heat Pre-dominant Zone
Compressor Status
Boundary Set-point
ON
OFF
4. PV Based Strategy
In this strategy, the compressor is switched to cool down the air temperature. The controller switches the compressor ON
or OFF based on the comparison between the et emperature values. Refer Figure below. Measured & S T 5.3
The compressor is turned ON if the chamber air temperature value is above the Temperature SP by an amount set by the
parameter 'Compressor Set-point'. That is;
Compressor Switch - ON Level = (Temperature SP) + (Compressor Set-point)
Figure 5.3
Measured Temperature
Temperature SP
Compressor Switch-ON Level
Compressor Switch-OFF Level
Compressor Switch-ON Level = 20.0 + 1.0 = 21.0°C
Temperature SP = 20.0°C
Compressor Set-point = 1.0°C
Compressor Hysteresis = 1.2°C
Compressor Switch-OFF Level = 21.0 - 1.2 = 19.8°C
Compressor Status
OFF
ON
20.0
19.8
21.0
°C