Carrier 38AU - Manual (Page 28)

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Comfort Alert Diagnostic Module
The Comfort Alert Diagnostic Module (CADM) monitors and
analyzes data from the Copeland Scroll ® three-phase compres-
sor and the thermostat demand. The CADM also provides a
3-minute anti-recycle time delay to compressor cycling.
The CADM detects causes for electrical and system related
failures without any sensors. Flashing LEDs communicate the
Alert codes to guide service technicians in accurately and
quickly troubleshooting the system and determining root cause
for the failure.
Inputs to the CADM include 24-vac power, thermostat Y1,
compressor contactor coil (common side) and compressor
power leads (from the compressor contactor).
Control of the compressor contactor coil is through a
normally-closed (power on the module) contact between
terminals P and C.
Communications of status and alert conditions is through three
LEDs located on the top edge of the module housing (see
Fig. 26): POWER (green), ALERT (yellow), and TRIP (red).
The POWER LED indicates the presence of control power to
the CADM.
Fig. 26 — CADM Housing/LED Locations
The ALERT LED indicates an abnormal condition exists in the
system through a flash code. The ALERT LED will blink a
number of times consecutively, pause and the repeat the
process. The number of blinks, defined in Table 13, correlates
to a particular abnormal condition; troubleshooting tips are
provided for each Alert code. Reset of the ALERT may be
automatic or manual. If the fault condition causing the Alert is
self-corrected, the Alert code will be removed and the CADM
will automatically reset and allow the system to restart
normally. Manual reset requires that main power to the 38AU
unit be recycled after the cause for the Alert condition has been
detected and corrected.
The TRIP LED indicates either a time-delay period is currently
active (RED LED is blinking) or the module has locked out the
compressor (RED LED is on steady). A lockout condition will
occur when the CADM detects a thermostat demand at input Y
but there is no power at the compressor line terminals T1 or T2
or T3. This lockout can occur due to a safety switch (LPS or
HPS) opening and de-energizing the compressor contactor, the
compressor-motor internal overload opens, or other internal
power interruption has occurred. Reset of the TRIP LED
requires that unit main power be recycled after the loss of
power to the compressor condition has been detected and
corrected.
Simultaneous Blinking of YELLOW and RED LEDs indicates
control power input to the CADM is low. Check control circuit
transformer and wiring.
Troubleshooting the CADM Wiring – Flashing LEDs also
indicate wiring problems to the CADM. See Table 14 for
discussion of additional LED flash codes and troubleshooting
instructions.
Input Terminal Voltage
Control
Power
R 24-V
Control
Common
C 24-V
Cooling Y 24-V
Contactor
Coil
P 24-V
Line A T1 Line
Line B T2 Line
Line C T3 Line
POWER
(GRN)
ALERT
(YEL)
TRIP
(RED)