Unit installation

53
8. When a compressor must be switched on the algorithm takes from the available compressors the less used
one (not blocked by alarm or timer). This is not applicable if the set up parameter M24 says no compressor
hours equalisation.
9. When a compressor must be switched off the system takes the more used one. This is not applicable if the
set up parameter M24 says no compressor hours equalisation.
10. Maximum number of compressor is set to 8.
Compressor Switch on procedure
RECIPROCATING compressor (M14 = 1)
• Check the minimum time before different compressor insertion (M23) is elapsed.
• Switch on circuit less used fan or first fan depending on setup parameter M38.
• Wait 20 seconds.
• Switch on compressor and liquid solenoid or Liquid Injection ports.
• Enable PI control of discharge pressure. At the beginning the output of the controller is locked to 25% in
stepless
control or at unloading capacity in step control.
Compressor switch on and off limitation
The table explains the system limitation to change status of compressors.
Those changes are required by the control algorithm, and are obtained through software procedures; but
compressors are not always available for these changes.
A cause of compressor not availability is an alarm situation or the minimum time on or off that not elapsed.
In other situations the control algorithm needs to switch off a compressor and the compressor is blocked on:
there is a minimum time between two stops' parameter in set up; this time should be elapsed before stopping the
compressor.
Initial
compressor
status
End
compressor
status
Procedure to be
used to change
status
Min time before enabling procedure
OFF ON Switch on
Minimum time off (M40) from last stop. Is the
minimum time the compressor should stay off before
being started again
OFF ON with
unloader
Switch on
Minimum time off (M40) from last stop. Is the
minimum time the compressor should stay off before
being started again
ON OFF Pump down
Minimum time on (M41) from last start. Is the
minimum time the compressor should stay on before
being stopped.
ON with
unloader
OFF Pump down
Minimum time on (M41) from last start. Is the
minimum time the compressor should stay on before
being stopped.
ON ON with
unloader
- No limitation
ON with
unloader
ON - No limitation
Effective
power
(given by
chiller) In %
of chiller
power
100 50 75 Required power
(output of PI controller)
25
Step1
Step2
Step3
Step4
25
50
75
100