YORK YMC2 — MBC - NO LEVITATION

The OptiView panel shows MBC - NO LEVITATION. Both service manuals for the YMC2 print the message identically and list it among the Safety Shutdown messages, so there are no other display variants.

OptiView software has commanded MBC Levitation Mode ON, but the MBC is not confirming that levitation actually took place. The two manuals describe the missing confirmation differently: one states the meaning as Levitation commanded but the Rotation Allowed input is not high, while the YMC2 Mod B manual states that the MBC is not reporting Levitated within 15 seconds.

• OptiView software is commanding MBC Levitation Mode ON while the Rotation Allowed digital input from the MBC contacts is not reading high.
• The MBC is not reporting Levitated within 15 seconds after the Levitation Mode ON command.
• Per the first description, the fault is inhibited if no VSD DC Bus Voltage is present and during the first 15 seconds after the Levitation Mode ON command is sent.
• Per the YMC2 Mod B manual, the fault is prohibited when the MBC Alive input is not high, indicating the MBC unavailable.

• 15 seconds: the fault is inhibited during the first 15 seconds after the Levitation Mode ON command is sent; in the YMC2 Mod B manual, the MBC must report Levitated within 15 seconds.
• The fault can only be set when a VSD DC Bus Voltage is present, since it is inhibited when none is present.

The release path is identical in both manuals. Released when the chiller is stopped. The chiller can be started when the condition is released and the OptiView panel CLEAR FAULTS button is pressed. In short, the fault is only released once the chiller is stopped, and the CLEAR FAULTS button on the OptiView panel must be pressed before the chiller can be started again.