9: Mechanical zero
No
Yes
Mechanical zero must only be set to Yes if the compressor has a built-in spacer block and au-
tomatic Vi regulation. This way the travel of the capacity slide is automatically reduced by the
percentage (0-40%) entered in Manual zero. Thus corrected capacity is calculated and shown
correctly.
10: Manual zero
0 to 40%
For screw compressors without automatic zero point setting, it is possible to manually set a
"zero point" below which the compressor capacity slide is not allowed to fall during compres-
sor operation.
If the compressor has a built-in spacer block and automatic Vi regulation, Manual zero is used
to reduce the travel of the capacity slide by the entered percentage. Thus corrected capacity
is calculated and shown correctly. The value [0-40%] to be entered in Manual zero must be of
the following size:
Manual zero =
Max. movement of capacity slide
Length of spacer block x 100
See Table 48: Maximum movement of capacity slide.
For SAB 202, which has automatic zero point setting, the value 0% must be kept. See also 6:
Mechanical zero.
For SAB 120, 151, 193, 233, 283, 355 the configuration of Manual zero is now made auto-
matically when Rotatune is selected. See subsection 6.4.1. Drive6: Rotatune. The automatic
configuration of Manual zero may still be changed manually, but the setting will be overwrit-
ten after a restart.
11: Booster (screw compressors)
No
Yes
Yes means that the oil pump will run continuously during compressor operation. This allows
the capacity slide to be moved at low pressure conditions.
Note: SAB Mk3, SAB HR, SAB 202, VMY Mk3, SV/FV and GSV/SGC compressors are fitted
with differential pressure controlled oil pumps and do therefore not use this configuration
point.
12: Economiser (screw compressor)
No
Yes
Select this function if the compressor is connected to an economiser. Thus the economiser is
connected/disconnected according to compressor operation. The connection is important for
regulation of the compressor volume ratio.
13: Eco low cap (screw compressors)
0 to 100%
If the immediate slide position is higher than the set value, the economiser is connected. If
the slide position is the %-setting stated in the economiser Neutral zone below this value, the
economiser is disconnected.
Set-up
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Engineering manual - Unisab III 1.10
001930 en 2014.09
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