Carrier 38AF Series Installation Manual page 17

17
Control Module (CM) Operation
When voltage is applied the power LED (DSI) will continuously flash 1/4 second off. The module starts a 3-minute
compressor delay timer. This delay can be bypassed by pressing the override switch for at least 1/2 second. The
Status LED (DS3) must be flashing or the override switch will not function.
On a call for cooling, the control module checks for 24vac to be present at T1 for a period of 7 seconds. It also
checks that the 3-minute compressor delay has clasped or overridden and also checks the state of the HPS/COTP. If
on alarms are detected nor delays are active the module will energize the compressor contactor relay. A timer is
started to provide minimum 3½ minute compressor run period.
During compressor operation the module continuously checks the HPS/COTP state ( Status LED ( DS3)and K1 LED
(DS4) are "NO" steady). If the circuit poens (24 vac not present at T7) the module will immediately shut down the
compressor and display the alarm Alarm LED (DS2) "ON" steady ). Power must be cycled to restore normal control
operation.
The OPS state is ignored during the first 60 seconds of operation .After this time if the OPS is open (24 vac not
present at T9) the compressor will be shut down. Alarm LED (DS2) displays the state of the OPS. A double blink (2-
1/4 ) second blinks, I second 0ff) indicates the OPS is open . If the OPS opens during operation and remains open for
longer that 60 seconds the module will lockout unit operation and display the alarm. Power must be cycled to restore
normal control operation.
The LPS is monitored during a call for cooling . The LPS is ignored during the first 2 ½ minutes of operation . The
Alarm LED (DS2) displays the state of the LPS. A single blink (1/4 second on, 1 second off) indicates that the LPS is
open. If the LPS remains open after 2 ½ minutes or opens later during the call for cooling (24 vac not present at
T11) the module shuts down the compressor. The 3-minute compressor delay is started and the cycle repeats. If the
call for cooling remains and this LPS cycle is repeated 3 times the module will lock out and display the alarm. Power
must be cycled to restore normal control operation.
When the call for cooling is satisfied and the compressor has run for at least 3 ½ minutes the module shuts off the
compressor. The CM stats the 3-minute compressor delay timer.