On the display
The panel shows MBC - HIGH BEARING Z1 TEMPERATURE. The manuals print the message in this single form, and it is one of the YMC2's Safety Shutdown messages: it appears when the MBC has tripped the unit on bearing temperature. The Z1 in the message text refers to the bearing this shutdown monitors — the impeller-end axial magnetic bearing.
What it means
The impeller-end axial magnetic bearing has run hot: the MBC measured a temperature greater than 266ºF (130ºC) on it. When the shutdown sets, the MBC Fault contacts open — the control center documentation prints them as the MBC ESD Fault contacts. At the same time, the MBC remains in Levitation mode with the motor shaft levitated, and it stays that way until the VSD rotation signal indicates less than 10 Hz.
Why it appears
- The MBC detects a temperature greater than 266ºF (130ºC) on the impeller-end axial magnetic bearing. This overtemperature detection is the one cause the manuals assign to the message.
What to check
- Confirm that the shutdown has released: the release depends on the temperature alone, and it happens when the bearing temperature is less than 266ºF (130ºC).
- Note that the MBC holds the motor shaft levitated in Levitation mode while the message is active, and remains there until the VSD rotation signal indicates less than 10 Hz.
Setpoints and thresholds
- Trip point: the shutdown sets when the MBC detects a temperature greater than 266ºF (130ºC) on the impeller-end axial magnetic bearing.
- Release point: the shutdown is released when the temperature is less than 266ºF (130ºC).
- Levitation hold: the MBC remains in Levitation mode until the VSD rotation signal indicates less than 10 Hz.
Reset and restart
Release is automatic: This shutdown is released when temperature is less than 266ºF (130ºC).
The release depends on the temperature alone, not on any panel action. Once the condition is released, The chiller can be started when the condition is released and the OptiView panel CLEAR FAULTS button is pressed.
The way back is therefore: let the bearing temperature fall below 266ºF (130ºC), press the CLEAR FAULTS button on the OptiView panel, then start the chiller.
Questions engineers ask
What temperature trips MBC - HIGH BEARING Z1 TEMPERATURE on a YORK YMC2?
The MBC sets this Safety Shutdown when it detects a temperature greater than 266ºF (130ºC) on the impeller-end axial magnetic bearing. The shutdown releases again once the temperature is less than 266ºF (130ºC).
How do I clear the message and restart the chiller?
Wait until the bearing temperature is below 266ºF (130ºC) so the condition releases, then press the CLEAR FAULTS button on the OptiView panel. The chiller can be started once the condition is released and that button has been pressed.
Does the shaft lose levitation when this shutdown trips?
No. The MBC remains in Levitation mode with the motor shaft levitated until the VSD rotation signal indicates less than 10 Hz.
Which bearing does Z1 refer to?
The message concerns the impeller-end axial magnetic bearing, whose temperature the MBC monitors against the 266ºF (130ºC) trip value.
Messages next to this one
Source
Written from the manufacturer's manuals for the YORK YMC2; every number and designation on this page is checked against them before publication. The row of the manual this message comes from:
All YORK YMC2 messages: fault codes · YORK YMC2 documentation · YORK manuals