Carrier 24ANA 230V Line Power Disconnect Detection, Compressor Voltage Sensing

24ANA

The control is shipped with the brownout active. The change in status is remembered until toggled to a new status. A power down/power up sequence will not reset the status. It may be necessary to do the toggle twice to cycle to the desired state of the defeat.

230V Line (Power Disconnect) Detection

If there is no 230v at the compressor contactor(s) when the indoor unit is powered and cooling demand exists, the appropriate error code is displayed (see Table 6). Verify that the disconnect is closed and 230v wiring is connected to the unit.

Compressor Voltage Sensing

The control board input terminals labeled VS, VR and L2 on 24ANA7 models and VS and L2 on 24ANA1 models (see Fig. 6) are used to detect compressor voltage status, and alert the user of potential problems. The control continuously monitors the high voltage on the run capacitor of the compressor motor. Voltage should be present any time the compressor contactor is energized, and voltage should not be present when the contactor is de-energized.

Contactor Shorted Detection

If there is compressor voltage sensed when there is no demand for compressor operation, the contactor may be stuck closed or there is a wiring error. The control will flash the appropriate fault code.

24ANA7 Models, Compressor Thermal Cutout

The control senses the compressor voltage at VR and VS. When starting or running, a phase difference of the voltages on the inputs will indicate the thermal protector is closed. If the phase difference is 5 degrees or less for 10 seconds, the internal protector is open. The control de-energizes the appropriate compressor contactor for 15 minutes, but continues to operate the outdoor fan. The control Status LED will flash the appropriate code shown in Table 6. After

15minutes, with a call for low- or high-stage cooling, the appropriate compressor contactor is energized. If the thermal protector has not re-set, the outdoor fan is turned off. If the call for cooling or heating continues, the control will energize the compressor contactor every 15 minutes. If the thermal protector closes, (at the next 15 minute interval check), the unit will resume operation.

If the thermal cutout trips for three consecutive cycles, then unit operation is locked out for 4 hours and the appropriate fault code is displayed.

24ANA1 Models, Compressor Thermal Cutout

If the control senses the compressor voltage after start-up, and is then absent for 10 consecutive seconds while cooling demand exists, the thermal protector is open. The control de-energizes the compressor contactor for 15 minutes, but continues to operate the outdoor fan. The control Status LED will flash the appropriate code shown in Table 6. After 15 minutes, with a call for low- or high-stage cooling, the compressor contactor is energized. If the thermal protector has not re-set, the outdoor fan is turned off. If the call for cooling continues, the control will energize the compressor contactor every 15 minutes. If the thermal protector closes, (at the next 15 minute interval check), the unit will resume operation.

If the thermal cutout trips for three consecutive cycles, then unit operation is locked out for 4 hours and the appropriate fault code is displayed.

Low or High Contactor Open (24ANA7 models) / No 230V at Compressor (24ANA1 models)

If the compressor voltage is not sensed when the compressor should be starting, the appropriate contactor may be stuck open or there is a wiring error. The control will flash the appropriate fault code. Check the contactor and control box wiring.

24ANA7 Models Only, Compressor Start Detection

In low-stage, if the specified start voltage at VR terminal is not achieved, the start relay is de-energized after 1 second and the control will flash the appropriate fault code.

In high-stage, if the specified start voltage at VS terminal is not achieved, the start relay is de-energized after 1 second and the control will flash the appropriate fault code.

If the specified start voltage is not achieved for 3 consecutive low-stage starts, low-stage operation is locked out for 30 minutes. If the specified start voltage is not achieved for 3 consecutive high-stage starts, high-stage operation is locked out for 30 minutes. The control will flash the appropriate fault code.

Troubleshooting 24ANA7 units for proper switching between low- & high-stages

Check the suction and liquid pressures at the service valves. Suction pressure should be reduced by 5-10% when switching from low to high capacity. There should be a 10-20% increase in liquid pressure when switching from low to high capacity. Compressor current should increase 100-250% when switching from low to high-stage.

Troubleshooting 24ANA1 units for proper switching between low- & high-stages

Check the suction pressures at the service valves. Suction pressure should be reduced by 3-10% when switching from low to high capacity.

NOTE: The liquid pressures are very similar between low- and high-stage operation, so liquid pressure should not be used for troubleshooting.

Compressor current should increase 20-45% when switching from low- to high-stage. The compressor solenoid when energized in high-stage, should measure 24vac.

When the compressor is operating in low-stage the 24v DC compressor solenoid coil is de-energized. When the compressor is operating in high-stage, the 24v DC solenoid coil is energized. The solenoid plug harness that is connected to the compressor has an internal rectifier that converts the 24v AC signal to 24v DC.

DO NOT INSTALL A PLUG WITHOUT AN INTERNAL RECTIFIER.

Unloader Test Procedure

The unloader is the compressor internal mechanism, controlled by the DC solenoid, that modulates between high- and low-stage. If it is suspected that the unloader is not working, the following methods may be used to verify operation.

1.Operate the system and measure compressor amperage. Cycle the unloader on and off at 30 second plus intervals at the UI (from low- to high-stage and back to low-stage). Wait 5 seconds after staging to high before taking a reading. The compressor amperage should go up or down at least 20 percent.

2.If step one does not give the expected results, remove the solenoid plug from the compressor and with the unit run- ning and the UI calling for high-stage, test the voltage out- put at the plug with a DC voltmeter. The reading should be 24 volts DC.

3.If the correct DC voltage is at the control circuit molded plug, measure the compressor unloader coil resistance. The resistance should be 32 to 60 ohms depending on com- pressor temperature. If the coil resistance is infinite, much lower than 32 ohms, or is grounded, the compressor must be replaced.

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