YORK YK — LCSSS - Power fault

The panel shows LCSSS - Power fault; the service manual's fault table prints the same message as LCSSS - POWER FAULT. The message comes from the liquid cooled solid state starter (LCSSS) and is treated as a cycling shutdown: the manuals describe an automatic restart after coastdown rather than a manual restart procedure.

The LCSSS logic/trigger board monitors the compressor motor current in each phase and has detected that the current in one or more phases has decreased to less than 10% of the FLA. The messages list entry describes the low-current condition as lasting a minimum of one line cycle; the service manual's description of the same check specifies any one phase of motor current dropping below a threshold of 10% FLA for three line cycles.

The check is not live at every moment. It is inhibited during the first 4 s of system run and until the motor current is greater than 25% of the job FLA; the service manual spells the arming condition out as all three phases of motor current having exceeded 25% of FLA for one second, after the first four seconds of the chiller start. The check is also disabled just before the chiller is placed into coastdown, to prevent nuisance shutdowns.

• Many times this is a normal fault related to a storm or lightning.
• The output CTs are not reading current correctly.

1. Verify that the output CTs are reading current correctly — this is the check the manual lists under possible problems for this shutdown.

• Trip threshold: compressor motor current below 10% of FLA in one or more phases.
• Trip duration: a minimum of one line cycle (messages list); the service manual gives three line cycles.
• Inhibit and arming: inhibited during the first 4 s of system run and until the motor current is greater than 25% of the job FLA; the service manual describes this as all three phases exceeding 25% of FLA for one second.
• Disable: the check is disabled just before the chiller is placed into coastdown, to prevent nuisance shutdowns.

Restart is automatic. The chiller automatically restarts upon completion of system coastdown. The service manual words the action as a cycling shutdown: automatic restart after coastdown if the shutdown is no longer active and the compressor switch is still in the run position. No separate reset step is described for this message.