Danfoss VLT FC 103 Programming Manual page 154

Parameter Description
25-25 -Zone Delay
Range: Function:
delayed by the length of time
programmed. If the pressure increases to
within the NZ before the timer has elapsed,
the timer is reset and no destaging occurs.
25-26 ++Zone Delay
Range: Function:
60 [0 – Staging a fixed speed compressor creates a
sec. 300 momentary pressure peak in the system, which
*
sec. ] 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
60æs factory setting is appropriate in most
applications. In highly dynamic system a shorter
time may be desirable.
25-27 --Zone Delay
Range: Function:
30 [0 – Destaging a fixed speed compressor creates a
sec. 300 momentary pressure drop in the system, which
*
sec. ] 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 30æs
factory setting is appropriate in most
applications. In highly dynamic system a shorter
time may be desirable.
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.
25-31 Stage Function
Option: Function:
[0] Disabled
*
[1] Enabled If the Stage Function is set to [0] Disabled,
25-32 Stage Function Time, will not be activated.
®
VLT Refrigeration Drive Programming Guide
25-32 Stage Function Time
Range:
15
sec.
25-33 Destage Function
Option:
[0]
[1]
25-34 Destage Function Time
Range:
15
sec.
®
MG16H102 - VLT is a registered Danfoss trademark
Function:
[0 – The Stage Function Time is programmed to
300 avoid frequent staging of the fixed speed
*
sec.] compressors. The Stage Function Time starts if it
is [1] Enabled by 25-31 Stage Function, and when
the variable speed compressor is running at
Motor Speed High Limit, 4-13 Motor Speed High
Limit [RPM] or 4-14 Motor Speed High Limit [Hz]
(or at 4-11 Motor Speed Low Limit [RPM] or
4-12 Motor Speed Low Limit [Hz] if 7-30 Process
PID Normal/Inverse Control is programmed to
Inverse), with at least one fixed speed
compressor in the stop position. When the
programmed value of the timer expires, a fixed
speed compressor is staged.
Function:
Disabled
*
Enabled The Destage Function ensures that the lowest
numbers of compressors are running to save
energy. If the Destage Function is set to [0]
Disabled, 25-34 Destage Function Time will not be
activated.
Function:
[0 – The Destage Function Timer is programmable to
300 avoid frequent staging/destaging of the fixed
*
sec. ] speed compressors. The Destage Function Time
starts when the adjustable speed compressor is
running at 4-11 Motor Speed Low Limit [RPM] or
4-12 Motor Speed Low Limit [Hz] (or 4-13 Motor
Speed High Limit [RPM] or 4-14 Motor Speed High
Limit [Hz] if is programmed to Inverse), with one
or more fixed speed compressors in operation
and system requirements satisfied. In this
situation, the adjustable speed compressor
contributes little to the system. When the
programmed value of the timer expires, a stage
is removed.
F VLT pump
F
min
Illustration 3.64
Pump
switch-o
De-stage
timer period
153
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