MICROPROCESSOR CONTROLLER
The microprocessor control system is specifically designed for single and dual stage systems. The control system interfaces with a conventional type thermostat.
•Unit shall be complete with self-contained low- voltage control circuit
•Unit shall incorporate a lockout circuit which provides reset capability at the space thermostat or base unit, should any of the following standard safety devices trip and shut off compressor.
-Loss-of-charge/Low-pressure switch
-High-pressure switch
-Condensate Overflow protection switch
•Unit shall operate with conventional thermostat designs and have a low voltage terminal strip for easy hook-up.
•Unit control board shall have on-board diagnostics and fault code display.
•Standard controls shall include anti-short cycle and low voltage protection
•Control board shall monitor each compressor and refrigerant safety switch independently.
•Control board shall have random start feature
•Control board shall retain last 5 fault codes in non volatile memory which will not be lost in the event of a power loss.
OPERATION
For cooling the room t-stat energizes the low-voltage circuit between “R” & “Y1”.
The call is passed to the unit microprocessor control, which then determines whether the requested operation is available and, if so, which components to energize.
CONTINUOUS BLOWER
By setting the room t-stat fan switch set to “ON”, the supply air blower will operate continuously. With the room t-stat fan switch set to “AUTO”, the blower is energized whenever a cooling operation is requested. The blower is energized after any specified delay associated with the operation.
When energized, the indoor blower has a minimum run time of 30 seconds. Additionally, the indoor blower has a delay of 10 seconds between operations.
When the room t-stat calls for cooling, the low-voltage control circuit from “R” to “Y1”and “G” is completed. The compressor and fan motor are energized. After completing the specified fan on delay for cooling, the microprocessor control will energize the blower motor.
Once the room t-stat has been satisfied, it will de- energize “Y1”. If the compressor has satisfied its minimum run time, the compressor and fan de- energize. Otherwise, the unit operates the cooling system until the minimum run time for the compressor has been completed. After the compressor de- energizes, the blower is stopped following the elapse of the fan-off delay for cooling.
To be available, a compressor must not be locked-out due to a high-pressure switch; low- pressure switch; condensate overflow switch; and the anti-short cycle delay (ASCD) must have elapsed.
SAFETY SWITCHES
Each refrigerant system is monitored to ensure it does not operate outside of its intended operating parameters. Safety switches are handled as described below. All system errors override minimum run times for compressors.
High-Pressure Limit Switch
If a high-pressure limit switch opens, the microprocessor control de-energizes the compressor, initiates the ASCD, and stops the fan. If a call for cooling or heating is still present at the conclusion of the ASCD, the microprocessor control will re-energize the compressor and unit fan.
Should a high-pressure switch open three times within two hours of operation, the microprocessor control will permanently lock-out the compressor. The system must be manually reset by de-energizing the 24 volt power to unit, or turning the room t-stat to the “OFF” position then back to cooling position. The microprocessor control will flash a fault code indicating a high-pressure lock-out.
Low-Pressure Limit Switch
The low-pressure limit switch is not monitored during the initial 30 seconds of compressor operation. After the initial 30 seconds have passed, the microprocessor control will monitor the low-pressure switch for another 30 seconds. If the low-pressure switch fails to close after the 30 second monitoring phase, the microprocessor control will de-energize the compressor, initiate the ASCD, and stop the fan.
Once the low-pressure switch has been proven (closed during the 30-second monitoring period as
