8.6 Carlyle Electronic Module
The LonCEM or Carlyle Electronic Module
(CEM) should be used as noted in section 6
with the following exception. The motor and
common termination on the module must be
jumpered with a standard 5K resistor. This
allows the module to maintain all of its func-
tionality with the exception of motor cooling
and motor over temperature control. The motor
cooling valve will still be required. It should be
piped into the economizer service valve to
inject liquid should the discharge become too
hot.
8.7 Motor Selection
Please refer to the Carlyle performance
data for the brake horsepower required for
your application. The performance data dis-
plays compressor capacity with a return gas
temperature of 65°F (18°C) for all conditions
in both the economized and non-economized
tables. It does not give the actual evaporator
refrigeration effect. The liquid temperature at
the evaporator expansion valve is equal to
the saturated condensing temperature for
the non-economized data and the saturated
interstage temperature plus 10°F (5.6°C) for
the economized data. Please refer to the
latest Carlyle Compressor CarWin selection
software for more detailed compressor capaci-
ty information.
The 33, 39, 44, 48 and 54 cfm compressors all
require 1750 rpm 4 pole motors @ 60 Hz
(1450 rpm @ 50 Hz) while the 65, 78 and 88
cfm compressors use 3500 rpm 2 pole motors
@ 60 Hz (2900 rpm @ 50 Hz). The motor must
be a C-Face motor in order to mount with the
C-Flange.
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Although screw compressors have lower frictional
torque requirements than normal reciprocating com-
pressors, the screw compressor can have high start-
ing torque levels. This is especially true when the
suction pressure is high. A reciprocating compressor
will open and close its reed valves according to pres-
sure in the compression chamber versus the suction
side (down stroke) or discharge side (up stroke). With
a screw compressor, the suction gas will be fully
compressed regardless of the suction and discharge
pressures relative to the compression pocket. This is
because there are no discharge reeds to open the
pocket to discharge when the pressure in the com-
pression pocket exceeds the discharge pressure.
Carlyle recommends the use of a high start torque
C-Face motor to ensure starting of the compressor.
The motor starting torque should supply a
minimum 170% of motor full load torque.
Higher
torque values may be necessary, especially for low
temperature R-404A/R-507 applications. Also, select
a motor which can handle the pulldown required for
the application, especially for low temperature appli-
cations. The motor should be able to handle the
break horsepower required for a minimum of 20°F
(11.1°C) saturated suction temperature,
above
design saturated suction temperature at design satu-
rated condensing temperature.
36