3.5. Compressor control - user functions
3.5.1 External starting permission - immediate stop
The input must be connected for the compressor to run in Manual, Auto or Remote. If this in-
put is opened during operation the compressor stops immediately.
When the input is open Stopped appears in the bottom line of the display.
3.5.2 External starting permission - normal stop
This input and External starting permission - immediate stop must be connected before the
compressor is going to start in Auto or Remote but it can be started in Manual mode.
If the input has not been connected, the display will show Stopped in the bottom line. If the
input is opened during operation, the compressor capacity will be decreased to minimum and
the compressor will stop on its Delay before stop timer.
In case the input Capacity down blocked is connected, the compressor will not reduce capacity
once the input External starting permission - normal stop is opened.
3.5.3 Capacity down blocked
This function is enabled in Setup/configuration/Plant/Cap down blocked.
When the compressor is in maximum capacity in Auto or Remote it can be locked in this state
by closing a digital input. See wiring diagrams. The input overrules External starting permis-
sion - normal stop.
If the compressor runs in limited operation (a limiting function is active), it will however re-
duce its capacity. When the state of operation is back to normal, the compressor will return to
full load. See also 3.2. Limiting functions.
If the input is connected while the compressor is ready to start in Auto or Remote, the com-
pressor will be started by force irrespective of actual regulator settings.
In case the chiller and flow condenser function have both been configured, it will not be possi-
ble to use the capacity blocked function. See section 3.6. Compressor control - chiller func-
tions.
3.5.4 Power management system (PMS)
This function works in Manual, Auto or Remote operation. It is a kind of "an agreement to
start" system, consisting of one digital output PMS Request, which is set when the compressor
should start, and a digital input PMS feedback. This input must be set before the timer PMS
feedback expires in order for the compressor to start.
The shutdown PMS error is activated if the input PMS feedback has not been set before the
timer PMS feedback expires.
If the PMS feedback fixed is configured to No the feedback signal can be removed during op-
eration without stopping the compressor.
If the PMS feedback fixed is configured to Yes the feedback signal cannot be removed during
operation without stopping the compressor, having a PMS error shutdown.
3.5.5 Cold store function
This function is connected to the regulators for capacity regulation of the compressor. Usually,
the compressor is going to start in Auto or Remote/Multisab if the measured value is outside
the neutral zone and a capacity requirement exists.
Compressor control and surveillance
Engineering manual - Unisab III 1.10
001930 en 2014.09
123/319
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