Bryant 577D----A Sequence of Operation, Unit Operation Hazard, 577D-- --A

open or shorted at any time after initial validation, Status Code 53 will be displayed at amber STATUS LED.

Check for faults in wiring connecting sensor to OAT terminals. Using an Ohm meter, check resistance of thermistor for a short or open condition.

If thermistor is shorted or open, replace it to return the system to normal operation. If fault is in the wiring connections, correcting the fault will clear the code and return the system to normal operation.

NOTE: If fault condition is an open thermistor or a wiring problem that appears to be an open thermistor and the power to the unit is cycled off, the fault code will be cleared on the next power-up but the fault will remain and system operation will not be as expected.

This is because on power-up, the unit control cannot discern the difference between an open sensor or if a sensor is not installed.

Sequence of Operation

The 577D--A packaged unit is designed for installation with a communicating UI. This unit will not respond to commands provided by a common thermostat except under certain emergency situations described in Step 1—Start-Up and Troubleshooting.

The UI uses temperature, humidity and other data supplied from indoor and outdoor system components to control heating or cooling system for optimum comfort. The unit will be commanded by UI to supply airflow. The unit will operate the indoor blower at requested airflow for most modes.

INDOOR AIRFLOW ADJUSTMENTS

The nominal requested airflow for air conditioner operations will be 350 cfm per ton of nominal cooling capacity as defined by unit size. Actual airflow request will be adjusted from nominal using indoor and outdoor temperature and indoor humidity data to optimize the system operation for occupant comfort and system efficiency. Refer to UI literature for further system control details.

!CAUTION

UNIT OPERATION HAZARD

Failure to follow this caution may result in unit damage.

For cooling operation, the recommended airflow is 350 to 450 cfm for each 12,000 Btuh of rated cooling capacity. For heating operation, the airflow must produce a temperature rise that falls within the range stamped on the unit rating plate.

For gas heat operations, Table 3 shows the temperature rise in each gas heating mode. Refer to these tables to determine the desired heating airflow for the system being installed.

NOTE: Be sure that all supply-and return-air grilles are open, free from obstructions, and adjusted properly. Airflow can be changed using the UI. See UI installation instructions for more detail.

NOTE: Once the compressor has started and then has stopped, it should not be started again until 4 minutes have elapsed. The cooling cycle remains “on” until the room temperature drops to point that is slightly below the cooling control setting of the UI.

AIR CONDITIONER SEQUENCE OF OPERATION COOLING OPERATION

With a call for first stage cooling, the outdoor fan, and low stage compressor are energized. If low-stage cannot satisfy cooling demand, high-stage cooling is energized by the UI. After second stage is satisfied, the unit returns to low-stage operation until first stage is satisfied or until second stage is required again. When both first stage and second stage cooling are satisfied, the compressor will shut off.

NOTE: When two-stage unit is operating at low-stage, system vapor (suction) pressure will be higher than a standard single-stage system or high-stage operation.

NOTE: Outdoor fan motor will continue to operate for one minute after compressor shuts off, when outdoor ambient is greater than or equal to 100°F (38°C).

UTILITY INTERFACE WITH Evolution CONTROL

The utility curtailment relay should be connected to factory supplied pigtails (PINK, connected to R, VIOLET connected to Y2 on the control board) located in the low voltage splice box (See Fig. 16, 18 and 18). This input allows a power utility device to interrupt compressor operation during peak load periods. When the utility sends a signal to shut the system down, the UI will display “Curtailment Active”.

COMPRESSOR OPERATION

When the compressor is operating in low stage, the modulating ring is deactivated, allowing two internal bypass ports to close off 33% of the scroll compression area so the system operates at part load capacity. The 24-volt solenoid coil is de-energized in low-stage operation.

When the compressor is operating at high stage, the modulating ring is activated, sealing the bypass ports, which allows the compressor to operate at full load capacity. The 24-volt solenoid coil is energized in high stage operation.

CRANKCASE HEATER OPERATION (IF APPLICABLE)

The crankcase heater is energized during off cycle below 65_F (18_C) outdoor air temperature.

OUTDOOR FAN MOTOR OPERATION

The outdoor unit control energizes the outdoor fan any time the compressor is operating. The outdoor fan remains energized if a pressure switch or compressor overload should open. Outdoor fan motor will continue to operate for one minute after the compressor shuts off when the outdoor ambient is greater than or equal to 100_F (38°C).

TIME DELAYS-AIR CONDITIONER OPERATIONS The unit time delays include:

SFive minute time delay to start cooling operation when there is a call from the thermostat or user interface. To bypass this feature, momentarily short and release Forced Defrost pins.

SFive minute compressor recycle delay on return from a brown-out condition.

STwo minute time delay to return to standby operation from last valid communication (with Evolution only).

SOne minute time delay of outdoor fan at termination of cooling

mode when outdoor ambient is greater than or equal to 100_F (38°C).

SThere is no time delay between air conditioner staging from low to high and from high to low capacity; the compressor will change from low to high and from high to low capacity as demand dictates.

577D-- -- A

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