3.5 Application Example - Pack Controller
3.5.1 BASIC Cascade/Pack Controller
130BC400.10
Illustration 3.30
The BASIC Cascade/Pack Controller is used for up to three
compressors to control up to two on/off compressors
together with one variable speed compressor. The capacity
control is typically based on suction pressure feedback, but
it could also be e.g. a cold room temperature.
Fixed Lead Compressor
The BASIC Pack Controller allows the frequency converter
to control up to 3 compressors using the frequency
converter's two built-in relays. The variable compressor
(lead) is connected directly to the frequency converter, the
other 2 compressors are controlled by the two built-in
relays.
NOTE
Only one fixed speed compressor can be controlled with
the built-in relays. To control two fixed compressors, an
extra relay is needed via the MCB 105 Relay Option.
Bandwidth Management
In pack control systems, to avoid frequent switching of
fixed speed compressors, the desired system load is kept
within a bandwidth rather than at a constant level. The
Staging Bandwidth provides the required bandwidth for
operation. When a large and quick change in system load
occurs, the Override Bandwidth overrides the Staging
Bandwidth to prevent immediate response to a short
duration load change. An Override Bandwidth Timer can
How to Install
Operating Instructions VLT
®
CDS302 and CDS303
34
MG34M302 - VLT
®
is a registered Danfoss trademark/Commercial Compressor
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