On the display
The panel shows MBC - HIGH DC/DC TEMPERATURE. This is the only form of the text the manual prints for this model. It is listed in the fault tables both as a Cycling Shutdown and as a Safety Shutdown, so one display text covers two trip levels of the MBC DC/DC Converter board.
What it means
The message reports an overtemperature at the MBC DC/DC Converter board. The manual carries it at two levels: a cycling level, described as an overtemperature of the MBC DC/DC converter board, and a safety level, described as an overtemperature of the MBC DC/DC converter. When the safety level trips, the MBC ESD Fault contacts open. The MBC stays in Levitation mode with the motor shaft levitated until the VSD rotation signal is less than 10 Hz; only then does the MBC de-levitate the rotor.
Why it appears
- Cycling level — the MBC DC/DC Converter board temperature rises above 167ºF (75ºC). The OptiView control software identifies the condition from temperature data sent through the serial comms.
- Safety level — the MBC DC/DC Converter board temperature rises above 203ºF (95ºC) and stays there for 2 seconds continuous.
Setpoints and thresholds
- Cycling level trip: 167ºF (75ºC) at the MBC DC/DC Converter board.
- Cycling level release: 18ºF (10ºC) below the trip value.
- Safety level trip: above 203ºF (95ºC) for 2 seconds continuous.
- Safety level release: 5.4ºF (3ºC) below the trip value.
- De-levitation point: VSD rotation signal less than 10 Hz.
Reset and restart
The cycling shutdown is released once the DC/DC converter temperature has fallen 18ºF (10ºC) below the trip value. The safety shutdown is released when the DC/DC converter temperature drops 5.4ºF (3ºC) below the trip value; on that condition the manual states: The chiller can be started when the condition is released and the OptiView panel CLEAR FAULTS button is pressed.
Questions engineers ask
What does MBC - HIGH DC/DC TEMPERATURE mean on a YORK YMC2?
It reports an overtemperature at the MBC DC/DC Converter board. The manual lists the message both as a Cycling Shutdown and as a Safety Shutdown, so the same text can appear at a cycling level and at a safety level.
At what temperature does the YMC2 trip on MBC - HIGH DC/DC TEMPERATURE?
The cycling level trips when the MBC DC/DC Converter board temperature passes 167ºF (75ºC). The safety level trips when that temperature stays above 203ºF (95ºC) for 2 seconds continuous.
How do I clear MBC - HIGH DC/DC TEMPERATURE on a YMC2?
The cycling level is released when the DC/DC converter temperature falls 18ºF (10ºC) below the trip value. The safety level is released when the temperature falls 5.4ºF (3ºC) below the trip value, after which the chiller can be started once the CLEAR FAULTS button on the OptiView panel is pressed.
Why is the motor shaft still levitated after this safety shutdown?
The MBC keeps the motor shaft levitated in Levitation mode until the VSD rotation signal is less than 10 Hz, and it de-levitates the rotor at that point. The MBC ESD Fault contacts open when the safety level is set.
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