7
© 2012 Emerson Climate Technologies, Inc.
Printed in the U.S.A.
AE4-1287 R7
Application Engineering
BULLETIN
module will only inject liquid when required. When the
temperature decreases to an acceptable level, the
module will stop injecting.
3D Copeland Discus Digital™ with Demand Cooling
Demand Cooling can be used with 3D Discus
™
digital compressors without adding extra unloader
control circuitry. The Demand Cooling temperature
sensing probe must be installed to replace the
temperature sensing probe that is provided with the
Digital Compressor Controller (IDCM). The T1 to
T2 connection on the Digital Compressor Controller
should be jumpered with a 5 kOhm 1 Watt resistor.
This allows the Demand Cooling module to protect
against high discharge temperatures and inject liquid
when needed.
Performance Adjustment Factors
Since compressor discharge temperature depends
strongly on the return gas temperature, the amount
of injection and its effect on evaporator capacity and
mass flow will vary somewhat with return gas
temperature. The approximate effects of return gas
temperature on evaporator capacity and mass fl ow are
tabulated in Tables 3A and 3B for HCFC-22. These
factors should be applied to the 65ºF return gas capacity
and mass fl ow values in the published performance
data sheets.
Performance values for HFC-407A, HFC-407C and
HFC-407F are not provided in this bulletin. For actual
performance values refer to the "Online Product
Information" at www.emersonclimate.com. As a
general rule of thumb, Emerson Climate Technologies
recommends assuming that HFC-407A, HFC-407C and
HFC-407F produce about 10% to 15% less evaporator
capacity than R-22 for low temperature applications.
Demand Cooling Specifi cations
Demand Cooling is designed to operate and
protect the compressor within the evaporating and
condensing envelope identifi ed in Figure 2. Operating
setpoints and control actions are listed in Table 1.
Attached is the Demand Cooling Diagnostic
Troubleshooting Guide (Form No. 92-91)
See also:
Demand Cooling Installation Instruction Guides
Emerson Climate Technologies Publication Nos.
90-130 for 2D/3D Compressors
90-131 for 4D Compressors
90-133 for 6D Compressors
Figure 1 – Demand Cooling System
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