Danfoss ADAP-KOOL Drive Programming Manual page 204

3 Parameter Description
25-23 Fixed Speed Neutral Zone [unit]
Range:
10%* [1 - 100%]
3
25-24 +Zone Delay
Range:
120 sec.* [0-3000 sec.]
25-25 -Zone Delay
Range:
60 sec.* [0-3000 sec.]
25-26 ++Zone Delay
Range:
60 sec.* [0 – 300 sec. ]
25-27 --Zone Delay
Range:
30 sec.* [0 – 300 sec. ]
3.19.4 25-3* Staging Functions
Parameters for setting the Staging and Destaging functions used to avoid frequent staging and destaging of fixed speed compressors.
204
the override function for pressure drops. When the fine tuning is complete, the -Zone should be set
to the desired value. An initial value of 3˚C is suggested.
Function:
When the cascade control system is running normally and the frequency converter issues a trip
alarm, it is important to maintain the system head. The Cascade Controller does this by continuing
to stage/destage the fixed speed compressor on and off. Due to the fact that keeping the head at
the setpoint would require frequent staging and destaging when only a fixed speed compressor is
running, a wider Fixed Speed Bandwidth (FSBW) is used instead of SBW. It is possible to stop the
fixed speed compressors, in case of an alarm situation, by pressing the LCP OFF or HAND ON keys
or if the signal programmed for Start on digital input goes low.
In case the issued alarm is a trip-lock alarm then the Cascade Controller must stop the system
immediately by cutting out all the fixed speed compressors. This is basically the same as Emergency
Stop (Coast/Coast inverse Command) for the Cascade Controller.
Function:
Immediate staging of a fixed speed compressor is not desirable when a momentary pressure in-
crease in the system exceeds the neutral zone (NZ). Staging is delayed by the length of time
programmed. If the pressure drops to within the NZ before the timer has elapsed, the timer is reset
and no staging occurs.
Function:
Immediate destaging of a fixed speed compressor is not desirable when a momentary pressure drop
in the system exceeds the neutral zone (NZ). Destaging is delayed by the length of time program-
med. If the pressure increases to within the NZ before the timer has elapsed, the timer is reset and
no destaging occurs.
Function:
Staging a fixed speed compressor creates a momentary pressure peak in the system, which might
exceed the sum of the neutral zone and the +zone. It is not desirable to destage a compressor in
response to a staging pressure peak. The ++Zone Delay can be programmed to prevent staging
until the system pressure has stabilized and normal control established. Set the timer to a value that
allows the system to stabilize after staging. On the other hand the +Zone delay might be too long
to react on a high pressure peak why the ++ zone delay always should be shorter than + zone
delay. The 60s factory setting is appropriate in most applications. In highly dynamic system a shorter
time may be desirable.
Function:
Destaging a fixed speed compressor creates a momentary pressure drop in the system, which might
exceed the sum of the neutral zone and the -zone. It is not desirable to stage a compressor in
response to a destaging pressure drop. The --Zone Delay can be programmed to prevent staging
until the system pressure has stabilized and normal control established. Set the timer to a value that
allows the system to stabilize after destaging. On the other hand the +Zone delay might be too long
to react on a high pressure peak why the -- zone delay always should be shorter than - zone delay.
The 30s factory setting is appropriate in most applications. In highly dynamic system a shorter time
may be desirable.
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ADAP-KOOL Drive Programming Guide