Carrier 69NT40-561-300, Operation And Service Manual

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7–23 T-365
7.19 TROUBLESHOOTING P6-7 (DLV/DUV)
7.19.1 Digital Unloader Valve (DUV)
A failed digital unloader valve (DUV), which is normally closed,) or an internal seal failure of the compressor can
result in the unit running continually in the fully loaded mode causing it to undershoot its set point temperature.
Both of these can be checked out by running pre-trip test P6-7. When running P6-7, the controller is looking for the
differences in pressure and current draw between loaded mode and unloaded mode to make a judgment. If there
are no differences, then it will show fail.
To confirm which what has caused the test to fail, perform the following additional test.
1. Connect manifold gauge set to discharge and suction service valves.
2. Front seat the SSV and pump down the compressor.
3. Front seat the discharge Service Valve.
4. Disconnect DUV from the top of compressor and cap the compressor fitting with the fitting removed from the
service valve.
5. Using R134, pressurize the line to 50 psi (3.45 bar) at the suction service valve connection and check for
leaks at the DUV outlet fitting at the compressor.
6. Energize DUV by placing a magnet on the valve stem opening the valve. Pressure will drop.
If a magnet is not available, a jumper procedure can be used as follows:
1. Remove all 4 controller fuses (F1, F2, F3a, F3b).
2. Remove the KA6 wire from KA controller connector on the front of the controller.
3. Disconnect the X1 wire from the 24VAC side of transformer (black wire) and locate it away from the trans-
former.
4. Jumper between the black transformer wires to the KA6 wire removed from the connector.
5. Connect power to unit and turn circuit breaker on (DUV coil is now energized).
6. Pressure should drop.
7. Power circuit breaker off, reconnect wires and reinstall fuses.
If the valve opens and closes properly, the failure mode is with the compressor and it should be changed at the
earliest opportunity.
7.19.2 Digital Loader Valve and Unloader Valve (DLV/DUV)
The EDGE model also has a digital loader valve (DLV normally closed). A failed digital loader valve will result in the
unit’s inability to cool due to a reduction in refrigerant flow where a failed digital unloader valve / DUV (normally
closed) will result in the unit undershooting its set point due to its inability to unload the compressor.
Both of these valves can be checked out by running pre-trip test P6-7. If pre-trip test P6-7 fails then the following
checks need to be made to identify which of the valves has failed.
1. Connect manifold gauge set to Discharge and Suction service valves. Refer to Section 7.2 .
2. Using Code 41, Service function, Valve Override Control as follows:
a. Set the tIM (Override Time to ~5 minutes)
b. Set the PCnt: Detailed below
c. Display Code 03, Compressor Motor Current value
By monitoring the compressor amperage and pressure, the technician can determine which component has failed.
Set the PCnt (100%setting – DLV Capacity TEST)
If the compressor is able to load, the compressor amperage and the discharge pressure will rise and the suction
pressure will drop – DLV is okay. If discharge pressure does not rise, the DLV should be replaced.
The Digital Loader Valve Solenoid coil cycles: 0 to 0.6 amp DC (AC/DC current clamp)