117JOHNSON CONTROLS
FORM NO.: 6U6K-B01E-NB-EN
COMPRESSOR SEQUENCING
The cumulative run time of each system is stored to help
equalize average run hours between systems with 2 refrigerant
systems or in modular applications.
The systems will be prioritized in sequence based on different
system congurations (inverter system or xed speed system)
and run hours. In initial startup, the inverter compressor will
always be the rst compressor to load.
Each compressor in a tandem fixed speed system will be
assigned an arbitrary priority number 1, 2. The non-running
compressor within a system with the lowest priority number
will always be the next compressor to start. The running
compressor with priority number 1 will always be the next
to shut off. Whenever a compressor is shut off, the priority
numbers of all compressors will be decreased by 1 with wrap-
around. This control scheme assures the same compressor does
not repeatedly cycle on and off.
The priorities while loading compressors are listed as follows:
1.Idle inverter compressor;
2.Running inverter system with load lower than 60% of full
system load;
3.Idle compressor in tandem fixed speed system with one
compressor running;
4.Idle compressor in tandem fixed speed system with no
compressor running;
5.Inverter system below full load.
The micro will select the compressor with least run hours if
there’re more than one compressors being able to load. This
will only occur in modular applications.
TABLE 38 - SAMPLE CAPACITY CONTROL FOR 4 COMPRESSORS (6 STEPS)
STEP
SYSTEM 1 SYSTEM 2
INVERTER FIXED SPEED FIXED SPEED FIXED SPEED
0 OFF OFF OFF OFF
1 ON ↑ OFF OFF OFF
2 ON ON OFF OFF
3 ON ↑ ON OFF OFF
4 ON ON ON OFF
5 ON ON ON ON
6 ON ↑ ON ON ON
Notes
1.The inverter system will load to a stable platform (50Hz) in Step 1.
2.Step 2 is skipped when there’s no xed speed compressor in inverter system (80 & 100 kW units).
3.The running frequency of inverter system will increase in Step 3 and Step 6.
4.The compressor with less run hours in SYS2 will load in Step 4.
SECTION 9 – UNIT OPERATION
Cooke Industries - Phone: +64 9 579 2185 Email: sales@cookeindustries.co.nz Web: www.cookeindustries.co.nz
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