Figure 2: Loaded Operation
Enters Compressor
Passes Through Body
Into Valve Plate
Compressed by Pistons
Exits Compressor
Nomenclature
The Copeland Discus digital compressor model
numbers are designated by a “D” or an “X” in the fourth
character, e.g. 3DS
D
R17ME-TFD, 4DA
D
F47KE-TSK or
4DJ
X
R28ME-TSK, 6DJ
X
R40ME-TSE. Discus digital
model numbers include additional information about the
compressor, consistent with the standard Discus model
nomenclature.
For more information on available Discus digital models
visit the website
Emerson.com
or contact your Emerson
representative.
Digital Performance
The nominal power consumption per nominal capacity
output varies. An example of the power required as a
percent of load is shown in
Figure 3
for a 3D Discus
digital compressor.
Operating Envelope
The operating envelopes for Discus digital compressors
are the same as the standard Discus compressor
envelopes. The head fan, return gas and oil cooler
requirements are the same as those for the standard
Discus compressors.
Control
Capacity modulation is achieved by energizing and de-
energizing the solenoid valve. When the solenoid valve
is de-energized, the compressor capacity is 100%.
When the solenoid valve is energized, the compressor
capacity is zero. Therefore, the capacity achieved is the
time average capacity, which is a variable from 10 –
100% on a 3D. Example: If you have a 20-second cycle
and the solenoid is de-energized for 16-seconds, and
then energized for 4-seconds, the resulting capacity will
be approximately 80%.
For 4D models one bank of the compressor remains
loaded 100% while the digital bank will modulate 0-
100% to provide the additional capacity. On a 6D with
blocked suction the blocked suction bank will unload
when demand capacity is less than 67% and load when
the demand capacity is higher than 67%. The digital
bank will continue to load and unload providing
continuous capacity across the 33-100% range.
Figure 2 Copeland Discus Digital Loaded View (shown on a Copeland 3D Discus compressor)
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