3.4. Compressor control - reciprocating compressors
3.4.1 Start sequence
There is no particular starting up sequence for reciprocating compressors. However, some
alarms are delayed at start-up.
Alarm surveillance
During start the following alarms are delayed:
Low oil pressure 60 sec.
High oil pressure 20 sec.
Low suction gas superheat 20 sec.
High suction gas superheat 300 sec.
Low/high oil temperature 300 sec.
Low discharge gas superheat 300 sec.
Low/high intermediate dis-
charge temperature
300 sec.
See also section 6.5. Timers.
The following descriptions of the various functions must be compared with the wiring dia-
grams where the activating connections are included.
3.4.2 Oil return
The solenoid valve for oil return from the oil separator/oil reservoir to the compressor will be
open when the compressor starts and an ON signal is issued to one digital input (or for two-
stage compressors two digital inputs).
For one-stage compressors, only the digital input for high pressure oil return is used. In this
case, the input must be ON before the digital output oil return is set.
For two-stage compressors where both the LP and HP part may have their own oil separator,
the digital inputs intermediate pressure oil return and high pressure oil return are used. In
this case, both inputs must be ON before setting the digital output for oil return.
The opening of the solenoid valve(s) for oil return can be combined with an adjustable time
delay. At compressor start the output(s) for oil return is/are not opened until the time set in
the Oil return timer has expired. The time delay function will be disconnected if the timer Oil
return is set for 0 seconds or when the digital inputs for intermediate and high pressure oil
return are OFF.
The time delay Oil return is set in the timer picture Setup/Timers/Timer setup.
3.4.3 Start unloading system for TCMO 28 compressor
TCMO 28 reciprocating compressors have a unique unloading system which ensures low start-
ing torque and a correct balance between high and low pressure cylinders during part load.
When the compressor is stopped during start-up and at loading stages below or at 50%, a hot
gas bypass valve “B” is activated to ensure this. See information sheet for outputs in the wir-
ing diagrams.
3.4.4 Additional steps on SMC compressors
From SMC 104 to SMC 108 the first capacity step is divided in two so that the compressor
starts on one cylinder. The other cylinder is used to connect changes in capacity stages. SMC
112 and 116 starts on two cylinders and the other two are used to connect changes in capaci-
ty steps. See the wiring diagrams.
Compressor control and surveillance
Engineering manual - Unisab III 1.10
001930 en 2014.09
117/319
To Next Page
Loading...
Need help?
General
