Danfoss VLT FC 103 - 10.8 Fuses, Circuit Breakers, and Switches

3.19.5 25-4* Staging Settings
Parameters determining conditions for staging/destaging
the
compressors.
25-42 Staging Threshold
Range: Function:
90%* [0 –
100%]
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
STAGE %
=
η
LOW
η
HIGH
× 100 %
to 100%, where n
LOW
is Motor Speed Low Limit
and n
HIGH
is Motor Speed High Limit.
Illustration 3.65
25-43 Destaging Threshold
Range: Function:
50%* [0 –
100%]
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
STAGE %
=
η
LOW
η
HIGH
× 100 %
to 100%, where n
LOW
is
Motor Speed Low Limit
and n
HIGH
is Motor Speed High Limit.
25-43 Destaging Threshold
Range: Function:
130BA367.10
3
5
0
1
Seconds
Variable speed
pump
Fixed speed
pump
Motor speed
high limit
Destaging
speed
Motor speed
low limit
Illustration 3.66
25-44 Staging Speed [RPM]
Option: Function:
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
STAGE
= η
HIGH
η
STAGE %
100
where n
HIGH
is
Motor Speed High Limit and n
STAGE100%
is the value of Staging Threshold.
25-45 Staging Speed [Hz]
Option: Function:
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
STAGE
= η
HIGH
η
STAGE %
100
where n
HIGH
is
Motor Speed
High Limit and n
STAGE100%
is the value of Staging
Threshold.
25-46 Destaging Speed [RPM]
Option: Function:
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
Parameter Description
VLT
®
Refrigeration Drive Programming Guide
154 MG16H102 - VLT
®
is a registered Danfoss trademark
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