Allied Air Enterprises 4AC16LT - Manual (Page 16)

506467-01 Issue 1008 Page 16
OPERATION
Outdoor unit and indoor blower cycle on demand from the
room thermostat. When the thermostat blower switch is
moved to the ON position, the indoor blower operates
continuously.
System Diagnostic Module
4 AC16LT units contain a diagnostic module for trouble-
shooting air conditioning system failures. By monitoring
and analyzing data from the compressor and thermostat
demand, the module can accurately detect the cause of
electrical and system related failure without any sensors.
If a system problem occurs, a flashing LED indicator
communicates the failure code.
LED Description
POWER LED (Green) indicates voltage is present at the
power connection of the module.
ALERT LED (Yellow) communicates an abnormal system
condition through a unique flash code. The ALERT LED
will flash a number of times consecutively, pause, and
then repeat the process. The number of consecutive
flashes correlates to a particular abnormal condition.
TRIP LED (Red) indicates there is a demand signal from
the thermostat but no current to the compressor is de-
tected by the module. The TRIP LED typically indicates
the compressor protector is open or may indicate missing
supply power to the compressor.
Interpreting the Diagnostic LEDs
When an abnormal system condition occurs, the diagnostic
module displays the appropriate ALERT and/or TRIP LED.
The yellow ALERT LED will flash a number of times
consecutively, pause, and then repeat the process. To
identify a flash code number, count the number of consecu-
tive flashes. Refer to Table 9 on page 17 and Table 10 on
page 18 for information on the flash codes.
Every time the module powers up, the last ALERT LED
flash code that occurred prior to shutdown is displayed for
60 seconds. The module will continue to display the
previous flash code until the condition returns to normal or
24VAC is removed from the module. TRIP and ALERT
LEDs flashing at the same time means control circuit
voltage is too low for operation.
24VAC Power Wiring
The diagnostic module requires a constant nominal 24VAC
power supply. The wiring to the module’s R and C terminals
must be directly from the indoor unit or thermostat.
Thermostat Demand Wiring
The diagnostic module requires a thermostat demand
signal to operate properly. The thermostat demand signal
input, labeled Y on the module, should always be con-
nected to the compressor contactor coil so that when the
coil is energized, the demand signal input is 24VAC. When
the coil is not energized, the demand signal input should be
less than 0.5VAC.
Miswired Module Codes
Depending on the system configuration, some ALERT
flash codes may not be active. The presence of safety
switches affects how the system alerts are displayed by
the module.
Miswiring the diagnostic module will cause false LED
codes. Table 11 on page 19 describes LED operation
when the module is miswired and what troubleshooting
action is required to correct the problem.