Johnson Controls SABROE Unisab III Control Engineering Manual page 312

Version no. Description
The Liquid slugging function known from screw compressors is now made
available for reciprocating compressors too. When the discharge temperature
drops 5°K in 5 seconds, an alarm is given, and when the temperature drops
10°K in 5 seconds, a shutdown is given. When a capacity step is engaged, the
liquid slugging alarm and shutdown are disabled for 60 seconds to avoid false
alarms. This is because the discharge temperature will drop because of the in-
creased capacity when a capacity step is engaged.
For HPO and HPC heat pumps (R717), the default oil temperature limits are
raised, i.e. low alarm to 45°K and low shutdown to 40°K.
For all reciprocating compressors, timer 15 Oil temperature low is made ad-
justable [0 - 300] seconds, with unchanged default value (300 sec.) If the Oil
temperature low timer is set to 0 seconds, then the shutdown/alarm monitor-
ing is always active.
For all reciprocating compressors, settings for the following oil return timers
have been adjusted: Oil return, Oil return open, Oil return close and Oil return
delay.
An error when using Unisab III for Ex use has been corrected. The Evolution
communication was disabled (reset to no) if control Mode was changed which
resulted in the connection between Unisab III and a PLC/Ex keyboard being
lost. This error is not found in version 1101.
A problem which sometimes made the heating element digital output flicker
has been corrected. The problem with flickering (DO20 quickly switching be-
tween on/off) could arise when the Profibus Extended protocol was used and
compressor start or stop by Profibus was used and command was set con-
stantly. The PLC code should only set a start or stop command as a pulse with
an approximate length of 1 sec. This was however not stated in the Profibus
Extended manual. The Unisab III code is now made more PLC/Profibus compli-
ant:
• After a compressor start command, 5500h have been executed, and the
compressor is started, Unisab will ignore a start command.
• After a compressor stop command, 0055h have been executed, and the
compressor is stopped, Unisab will ignore a stop command.
A data value was missing in the CSV file sent to the Smartphone App. The Low
shutdown for Oil Separator temperature has now been added.
For SAB 157HR, the plug valve logic for low main oil pressure has been cor-
rected. Main oil pressure logic now unloads the plug valve when the main oil
injection port SM1 is active.
The sequencing has been modified so the Compressor State does not shift to
"Running Overload" when the plug valve is unloaded. The "Low main oil pres-
sure" alarm delay has been changed from 600 seconds to 180 seconds.
Engineering manual - Unisab III 1.10
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Troubleshooting
001930 en 2014.09