Troubleshooting guide
MAGNUM VERSION 8 MANUAL REVISION 3.1
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Compressor with a Variable Frequency Drive (VFD)
7.4.2.
This option is specified in MCS-Config by selecting the Analog Output for the VFD in the “Compr
Speed or Modulate Hot Gas AO” cell in the Circuit Base screen.
The Magnum will control the compressor speed in the same matter as the compressor slide. The same
Setpoints will be used. This allows a fixed staged compressor’s capacity to be varied. See section 13 for
Setpoints associated with variable capacity control logic.
Example of a system with 3 variable Step Compressors
7.4.3.
(Example below assumes compressor 1 is the current lead compressor.)
STAGE 1
Compressor 1’s startup procedure has begun. Once on, the capacity will be adjusted from the minimum to
the maximum. All other compressors will be off. The steps Wanted On / Actual On will be 1 / 1.
STAGE 2
Compressor 2’s startup procedure has begun. Once on, the system capacity will be changed to the
calculated % and compressor 1 will be unloaded until it matches the calculated system capacity. Both
compressors will be varied from the calculated to the maximum. All other compressors will be off. The
steps Wanted On / Actual On will be 2 / 2. If the system capacity has been reduced to 45%, or the
calculated % (whichever is larger) and less capacity is needed, a compressor will be turned off and the
system capacity will be set to the 90% or the maximum and the system will return to Stage 1.
STAGE 3
Compressor 3’s startup procedure has begun. Once on, the system capacity will be changed to the
calculated % and compressors 1 and 2 will be unloaded until they equal the required capacity. All
compressors will be varied from the calculated to 100%. The steps Wanted On / Actual On will be 3 / 3. If
the system capacity has been reduced to 60%, and less capacity is needed, a compressor will be turned
off and the system capacity will be set 90% and the system will return to Stage 2.
7.5. Compressor Types
The compressor type is selected from a drop down list in the Compressor Information panel on the MAG
V8 screen.
Reciprocating Compressor with Oil
Reciprocating Compressor without Oil
Screw Compressor with Oil
Scroll Compressor