6.1 Carlyle Electronic Module (CEM)
The Carlyle solid-state electronic module
(115v-1-50/60 or 240v-1-50/60) is used for
primary control of the compressor contactor,
oil and economizer line solenoids, and
unloader and Vi coils. It also provides com-
pressor thermal safety protection.
Two versions of this module have been used.
The original Carlyle Electronic Module (CEM)
and the LonCEM Module. Both versions are
covered in detail in Appendix A and Appendix
B of this manual.
6.2 Discharge Temperature Control
Discharge temperature control and high tem-
perature protection are supplied by the CEM.
There are some applications where the dis-
charge temperature becomes so hot that it is
necessary to inject liquid directly into the screw
rotors. This is accomplished through the use of
a constant temperature desuperheating valve.
Refer to section 3.7 for selection and applica-
tion of this valve.The desuperheating valve bulb
must be strapped to the discharge line (as
close to the service valve as possible) and
insulated. The valve will maintain a discharge
temperature of 190°F (88°C). A normally
closed solenoid with an inlet strainer is required
upstream of the expansion valve.
The liquid feed header must be sized for
the entire desuperheating and motor cool-
ing load. Failure to do so can lead to com-
pressor overheating during high ambient
operation.
Section 6 — Motor and Discharge Temperature Control
6.3 Motor Cooling Control
Motor cooling control and high temperature
protection are supplied by the LonCEM/CEM.
Carlyle 06T screw compressors utilize an econ-
omizer cooled motor. Screw compressor tech-
nology allows access to intermediate pressure
part way through the compression cycle. The
Carlyle screw compressor uses this intermedi-
ate pressure access to pull vapor through a
subcooler and over the compressor motor.
This process (called an economizer cycle) pro-
vides liquid subcooling and motor cooling
(reducing the need for liquid injection). Due to
both these processes being done at an inter-
mediate pressure versus suction pressure, sig-
nificant increases in energy efficiency are real-
ized.
A typical economizer arrangement is shown
below. The flow to the screw compressor
motor is governed by an expansion valve that
is set to maintain 10 to 20°F (6 to 11°C) super-
heat above intermediate pressure. A liquid line
solenoid is required in front of the expansion
valve and must be normally closed (this valve
must be off when all compressors are off and
on when any compressor is on).
29
2.50
(63.5)
0.50
(12.7)
NO BENDS WITHIN
1.50" OF HEAD
3" (7.62 mm)
REINFORCEMENT
SPRING
OUTLET
INLET
0.31
(7.9)
MIN.
1.37
(34.8)
0.94
(23.9)
HEX
0.31
(7.9)
MIN.
0.3775/0.3805 DIA.
(9.588/9.665)
TYP. (INLET & OUTLET)
EACH CONNECTION
1.33
(33.8)
1.69
(42.9)
DESUPERHEATING VALVE
1.78
(45.2)
3.89
(98.8)
(38.1)
TO EVAPORATOR
ECONOMIZER
MAIN LIQUID
VAPOR OUT
TO COMPRESSOR
ECONOMIZER PORT
For parallel applications, an intermediate
header is required to distribute economizer
gas to each compressor. A solenoid valve is
required in the feed line to each compressor.
This valve must be normally closed and off
when the compressor is off to eliminate inter-
mediate to suction pressure leak back during
any compressor off cycle. This solenoid can
be controlled by the CEM.
If an economizer is not used, motor cooling
control is still required. Two cooling valves
should be installed in parallel, feeding the econ-
omizer port to eliminate thermal shock. One
EF28BZ005 (1 ton) valve is wired to be on any
time the compressor is on and the LonCEM
controls one EF28BZ007 (1.5 ton) valve.
Motor barrel insulation is recommended on
compressors with suction temperatures below
-15°F (-26°C) to prevent frost build-up and
condensation on the compressor motor barrel.
FOR REFERENCE ONLY
INCHES
[MILLIMETERS (mm)]