YORK YK — LCSSS - OPEN SCR

The display reads LCSSS - OPEN SCR; the manual's fault table also lists the wording LCSSS - Open SCR. It is a safety shutdown message shown by the control center when the Style B Liquid Cooled Solid State Starter (LCSSS) shuts the chiller down.

This is a safety shutdown from the Style B Liquid Cooled Solid State Starter (LCSSS): the starter logic/trigger board has detected an open SCR (Silicon Controlled Rectifier) in phase A, B, or C. Voltage across each SCR is monitored through an opto-coupler; the check becomes active after the first 40 seconds of starter operation, and the fault is annunciated when the signal stays low for 5 consecutive seconds. The open condition must exist continuously for 5 s to annunciate the fault, and this check is disabled when the chiller is shut down.

The manual explains that this exact wording is displayed when the fault data returned from the starter does not identify the phase in which the fault occurred — the case on starters whose Logic/Trigger Board carries an earlier eprom version; the fault data reaching the control center is a function of the eprom (U16) in that board. A newer eprom version in the Logic/Trigger Board returns fault data that identifies the phase, so the control center then displays a message naming the defective phase.

• Gate drivers not operating.
• Starting current value incorrect.
• Motor overloaded on start — the manual notes this has been a problem on screw compressors.
• Motor not connected.
• SCR gate open.
• Open input fuse.
• In certain applications, local power line conditions could interfere with the open SCR detection technique.

1. Verify operation of the gate drivers.
2. Verify that the starting current value is correct.
3. Ensure that the motor is not overloaded on start; the manual notes this has been a problem on screw compressors.
4. Verify that the motor is connected.
5. Verify that the gate of the SCR is not open.
6. Check for an open input fuse.

• Detection window: the check becomes active after the first 40 seconds of starter operation.
• Annunciation threshold: the open condition must exist continuously for 5 s (the monitored signal low for 5 consecutive seconds).
• This check is disabled when the chiller is shut down.
• To help eliminate nuisance trips, this shutdown can be disabled from the OptiView™ control center — refer to the service form for your style of chiller.
• Interference from local power line conditions requires a qualified service technician to disable this check.

The chiller can be started after the condition has been corrected and the chiller is in a stopped state. After the coastdown period, restart via Compressor Switch Stop/Reset then Start if the shutdown is no longer active.