If the current signal drops to -10% (2.4 mA), the chosen form of regulation will change (e.g.
suction pressure regulation, brine regulation, etc). If the signal exceeds -10% once more,
regulation will change back to capacity remote control. When Unisab III is configured to ca-
pacity set point, the start number changes to 0. The “old” starting number is stored and rein-
serted if Unisab III is configured differently from capacity set point control.
3.1.13 Climate compensation
This function can be used for both reciprocating and screw compressors without automatic Vi
regulation. The function is included in the picture Setup/Compr.Control and is further descri-
bed in chapter 6. Set-up.
The inlet temperature set point on the water side of plants which are regulated by brine tem-
perature or hot water temperature can be controlled by the outside temperature. This re-
quires a 4-20 mA temperature transducer, which is connected to the current inlet in Unisab III
as shown in the wiring diagrams in the back of this manual.
Use a standard temperature transducer with a suitable temperature range, e.g. -30 - +25°C
as shown in Fig. 14. Note that the points of discontinuity in the diagram will be determined by
the transducer measuring range as seen in examples 1 and 2 below.
T inlet
Sp 1 (-5°C)
Sp 2
(+25°C)
4 mA
(-30°C)
20 mA
(+25°)
T out
Fig. 14: Transducer measuring range
No further compensation will be made once the outside temperature is above the top point of
discontinuity and below the bottom point of discontinuity.
The factor by which the outside temperature should influence the inlet temperature positively
or negatively must be set in the Brine, Hot water or User regulator.
In the picture Setup/Compr. Control, select Control on = Process out (brine) or Hot water, or
(with User regulator) Ext. Cool/Ext.Heat as well as Climate compensation = “Yes” in the pic-
ture Setup/Compr. Control.
Example 1:
On a water cooling unit, the inlet temperature is to be corrected by the outside temperature.
• If the outside temperature is +30°C or more, the inlet temperature should be +4°C.
• If the outside temperature is +0°C or less, the inlet temperature should be +12°C.
In the menu Setup/Compr. Control, set Control on to Process out and Climate compensation
on Yes. Select an outside sensor with a range of 0 - +30°C.
Compressor control and surveillance
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Engineering manual - Unisab III 1.10
001930 en 2014.09
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