COOLING OPERATION
First-Stage Cooling Operation
During first-stage cooling operation, the control will receive a thermostat signal at the Y1 terminal. The control will energize the M compressor output terminal. This signal energizes the coil on the compressor con- tactor causing the compressor to run.
Second Stage Cooling Operation
During second-stage cooling operation, the control will receive a ther- mostat signal from Y1 and Y2 inputs. The control will energize both the M and M2 compressor output terminals. The M signal energizes the compressor contactor causing the compressor to run. The M2 signal applies 24VAC to the rectifier plug for the compressor solenoid allowing the compressor to operate in second stage.
HIGH-PRESSURE SWITCH FAULT
The AC Unit is equipped with a high-pressure switch that is connected to the control at the HPS terminals. If the high-pressure switch opens for more than 40 milliseconds, the control will de-energize the compres- sor and store and display the appropriate fault code. If the pressure switch closes and a thermostat call for compressor operation is present, the control will apply the five-minute anti-short cycle delay timer and start the compressor when the timer expires. If a call for compressor operation is initiated while the high-pressure switch is open, the control will use the logic associated with a high-pressure switch opening during a call for compressor operation.
When the compressor is started following a high-pressure switch fault, the control will start a six-hour timer based on accumulated compressor run time. If the control senses another opening of the high-pressure switch before the timer expires, it will cause a soft lockout condition. The second opening of the high-pressure switch must be greater than 160 milliseconds for the lockout to occur. If the second opening is between 40 and 160 milliseconds, the control will de-energize the com- pressor but not cause a soft lockout condition. If the control does not sense a second high-pressure switch opening before the six-hour timer expires, the timer and counter will be reset.
LOW-PRESSURE SWITCH FAULT
The AC unit is equipped with a low-pressure switch which is connected to the control at the LPS terminals. If the low-pressure switch opens for more than five seconds, the control will cause a soft lockout condition and display the appropriate fault codes. If the control experiences multi- ple soft lockouts the control will enter a hard lockout as described in another section of this document. However, the control will ignore the low pressure switch input and not cause a soft lockout condition if it opens during the following conditions.
•First two minutes of compressor operation.
•While TEST input pins are shorted while any thermostat input Y1 or Y2 signal is being received.
OUTDOOR AMBIENT TEMPERATURE SENSOR
Ambient temperature sensor is used in communication applications only. It is used to display outdoor temperature to the home owner via the communicating thermostat.
•Has no effect on operation.
•Not required for operation, but a fault code will be displayed when sensor is not connected or if sensor is shorted.
