Danfoss VLT FC 103 Programming Manual page 155

Parameter Description
3.19.5 25-4* Staging Settings
Parameters determining conditions for staging/destaging
the compressors.
25-42 Staging Threshold
3 3
Range:
90% [0 –
*
100%]
25-43 Destaging Threshold
Range:
50% [0 –
*
100%]
154
VLT
Function:
When adding a fixed speed compressor, in order
to prevent an overshoot of pressure, the variable
speed compressor ramps down to a lower speed.
When the variable speed compressor reaches the
"Staging Speed" the fixed speed compressor is
staged on. The Staging Threshold is used to
calculate the speed of the variable speed
compressor when the "cut-in point" of the fixed
speed compressor occurs. The calculation of the
Staging Threshold is the ratio of 4-11 Motor Speed
Low Limit [RPM] or 4-12 Motor Speed Low Limit
[Hz] to 4-13 Motor Speed High Limit [RPM] or
4-14 Motor Speed High Limit [Hz] expressed in
percent.
Staging Threshold must range from
η
LOW
η STAGE % = × 100 %
η
HIGH
to 100%, where n is Motor Speed Low Limit
LOW
and n is Motor Speed High Limit.
HIGH
Illustration 3.65
Function:
When removing a fixed speed compressor, in
order to prevent an undershoot of pressure, the
variable speed compressor ramps up to a higher
speed. When the variable speed compressor
reaches the "Destaging Speed" the fixed speed
compressor is destaged. The Destaging Threshold
is used to calculate the speed of the variable
speed compressor when the destaging of the
fixed speed compressor occurs. The calculation of
the Destaging Threshold is the ratio of 4-11 Motor
Speed Low Limit [RPM] or 4-12 Motor Speed Low
Limit [Hz] to 4-13 Motor Speed High Limit [RPM] or
4-14 Motor Speed High Limit [Hz] expressed in
percent.
Destaging Threshold must range from
η
LOW
η STAGE % = × 100 %
η
HIGH
to 100%, where n is Motor Speed Low Limit
LOW
and n is Motor Speed High Limit.
HIGH
MG16H102 - VLT
®
Refrigeration Drive Programming Guide
25-43 Destaging Threshold
Range:
25-44 Staging Speed [RPM]
Option:
0 N/A Readout of the below calculated value for Staging
Speed. When adding a fixed speed compressor, in
order to prevent an overshoot of pressure, the
variable speed compressor ramps down to a lower
speed. When the variable speed compressor reaches
the "Staging Speed" the fixed speed compressor is
staged on. Staging Speed calculation is based on
25-42 Staging Threshold and 4-13 Motor Speed High
Limit [RPM].
Staging Speed is calculated with the following
formula:
η
where n
is the value of Staging Threshold.
25-45 Staging Speed [Hz]
Option:
0 N/A Readout of the below calculated value for Staging
Speed When adding a fixed speed compressor, in
order to prevent an overshoot of pressure, the
variable speed compressor ramps down to a lower
speed. When the variable speed compressor reaches
the "Staging Speed" the fixed speed compressor is
staged on. Staging Speed calculation is based on
25-42 Staging Threshold and 4-14 Motor Speed High
Limit [Hz].
Staging Speed is calculated with the following
formula:
η
High Limit and n
Threshold.
25-46 Destaging Speed [RPM]
Option:
0 N/A Readout of the below calculated value for Destaging
Speed. When removing a fixed speed compressor, in
order to prevent an undershoot of pressure, the
variable speed compressor ramps up to a higher
speed. When the variable speed compressor reaches
the "Destaging Speed" the fixed speed compressor is
destaged. Destaging Speed is calculated based on
®
is a registered Danfoss trademark
Function:
Motor speed
high limit
Destaging
speed
Fixed speed
pump
Motor speed
low limit
0 1 3 5
Illustration 3.66
Function:
η
STAGE %
STAGE = η HIGH
100
is Motor Speed High Limit and n
HIGH
Function:
η
STAGE %
where n
STAGE = η HIGH
100
is the value of Staging
STAGE100%
Function:
Variable speed
pump
Seconds
STAGE100%
is Motor Speed
HIGH