and OCT faults will not be cleared. The code will continue to be flashed.
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 or heating demand exists, the appropriate fault code is displayed. Verify the disconnect is closed and 230v wiring is connected to the unit.
Compressor Voltage Sensing
The control board input terminals labeled VS and L2 (see Fig. 54) 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 may be a wiring error. The control will flash the appropriate fault code.
If the control senses the compressor voltage after start-up and is then absent for 10 consecutive seconds while cooling or heating 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 23. After 15 minutes, with a call for low or high stage cooling or heating, the 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.
No 230V at Compressor Contactor
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.
Troubleshooting 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.
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 DC signal to 24v AC. 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 User Interface (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 the expected result is not achieved, remove the solenoid plug from the compressor and with the unit running and the User Interface or thermostat calling for high stage, test the voltage output at the plug with a DC voltmeter. The read- ing 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.
Temperature Thermistors
Thermistors are electronic devices which sense temperature. As the temperature increases, the resistance decreases. Thermistors are used to sense outdoor air (OAT) and coil temperature (OCT). Refer to Fig. 55 for resistance values versus temperature.
THERMISTOR CURVE
| 90 |
(KOHMS) | 80 |
70 |
| 60 |
RESISTANCE | 50 |
20 |
| 40 |
| 30 |
| 10 |
| 0 |
0 | 20 | 40 | 60 | 80 | 100 | 120 |
(-17.77) | (-6.67) | (4.44) | (15.56) | (26.67) | (37.78) | (48.89) |
| | TEMPERATURE °F (°C) | | |
A08054
Fig. 55 – Resistance Values Versus Temperature
If the outdoor air or coil thermistor should fail, the control will flash the appropriate fault code. (See Table 23.)
IMPORTANT: The outdoor air thermistor and coil thermistor should be factory mounted in the final locations. Check to ensure thermistors are mounted properly per Fig. 56 and Fig. 58.
Thermistor Sensor Comparison
The control continuously monitors and compares the outdoor air temperature sensor and outdoor coil temperature sensor to ensure proper operating conditions. The comparison is:
S In cooling if the outdoor air sensor indicates ≥ 10_F
(≥ 5.6_C) warmer than the coil sensor (or) the outdoor air sensor indicates ≥ 20_F (≥ 11_C) cooler than the coil sensor, the sensors are out of range.
SIn heating if the outdoor air sensor indicates ≥ 35_F (≥ 19.4_C) warmer than the coil sensor (or) the outdoor air sensor indicates ≥ 10_F (≥ 5.6_C) cooler than the coil sensor, the sensors are out of range.
If the sensors are out of range, the control will flash the appropriate fault code as shown in Table 23.
