YORK YMC2 — VSD - PHASE A MOTOR DCCT

The panel shows VSD - PHASE A MOTOR DCCT. The manuals print the message in this exact wording and capitalisation, with no other variants, and it is one of the unit's safety shutdown messages.

This is the VSD's check that current is genuinely flowing to the motor once a start is commanded; the fault table sums it up as a failed check of the motor phase A DCCT cable and current. At the beginning of the run command the VSD measures the motor current in each phase. The reading at that instant should be very low, and it is kept as the zero current value for the rest of the run time. The VSD then monitors the current for the next 1.5 seconds to make sure a minimum amount of current is flowing to the motor. If a minimum of 25 amps peak is not detected by the end of that window, the shutdown is generated. Because the test waits for that first rise of current, it also tells the control whether the cable at the motor DCCT is connected.

• The shutdown exists to determine if the cable at the motor DCCT is connected — a cable that is not connected is the condition it is designed to detect.
• The shutdown is generated 1.5 seconds after the motor run command if the motor current does not exceed 25 A.

1. Check that the cable at the motor DCCT is connected — this is the condition the shutdown is designed to determine.

• 25 amps peak — the minimum motor current that must be detected within the monitoring window; below it, the shutdown is generated.
• 1.5 seconds — the monitoring window that follows the motor run command.

The shutdown stands until the condition clears. When the condition clears, the chiller can be started after the clear faults button is pressed. That is the only recovery step the manuals give for this message.