PPI HumiTherm-c Series User Manual

36
This strategy eliminates the dependency on the user for switching off the compressor (for saving valuable electrical energy)
when not required. The Compressor Set-point for this parameter value is usually set to the maximum expected Ambient
Temperature. It is usually not required to switch-on compressor if the desired Temperature is significantly above the Ambient
Temperature and thus a considerable energy saving can be achieved by keeping the compressor OFF.
2. Dry Bulb PV Strategy
In this strategy, the controller provides three user settable parameters, viz. Compressor Set-point (CP.SP), Hysteresis
(CP.HY) & Time Delay (t.dLY) in PAGE 13 parameter list. The Compressor ON or OFF state is determined by comparing the
Dry Bulb PV with the Compressor Switch-on Level and the Compressor Switch-off Level. The Compressor Switch-on and
Switch-off levels are determined using Dry Bulb SP (db.SP), Compressor Set-point (CP.SP) and Hysteresis (CP.HY), as
below.
Switch-on Level = Dry Bulb SP (db.SP) + Compressor SP (CP.SP)
Switch-off Level = Switch-on Level - Hysteresis (CP.HY)
The Hysteresis introduces a dead-band between the Compressor Switch-on Level and Switch-off Level. The following Figure
8.3 illustrates the compressor ON-OFF operation.
Figure 8.3
Switch-on Level
(Dry Bulb SP + Compressor SP)
Dry Bulb SP
OFF
Hysteresis
ON ON
Switch-off Level
(Switch-on Level - Hysterisis)
Examples
1) For Dry Bulb SP = 20.0°C, Compressor SP = 1.0°C & Hysteresis = 1.2°C;
Switch-on Level = 20.0 + 1.0 = 21.0Dry Bulb SP + Compressor SP = °C
Switch-off Level = Switch-on Level - Hysteresis = 21.0 - 1.2 = 19.8°C.
2) For Dry Bulb SP = 20.0°C, Compressor SP = 1.0°C & Hysteresis = 0.8°C;
Switch-on Level = 20.0 + 1.0 = 21.0Dry Bulb SP + Compressor SP = °C
Switch-off Level = Switch-on Level - Hysteresis = 21.0 - 0.8 = 20.2°C.
User Manual
HumiTherm-c (Temp+RH)
Figure 8.1
Compressor ON
Dry Bulb Set-point (°C.SP)
Compressor Set-point (CP.SP)
Dry Bulb SP < Compressor SP
Compressor ON
Figure 8.2
Compressor OFF
Dry Bulb Set-point (°C.SP)
Compressor Set-point (CP.SP)
Dry Bulb SP ≥ Compressor SP
Compressor OFF

PPI HumiTherm-c Series Specifications

General

Brand	PPI
Model	HumiTherm-c Series
Category	Controller
Language	English