ABB ACH580 Drives: Override Mode
Many deaths that occur in building fires are not the result of the fire but are, instead, resultant from smoke inhalation or intoxication from carbon monoxide or nitrous oxide. Managing smoke in these situations via airflow control can potentially help keep people alive and even protect the building from extensive damage.
ABB ACH580 drives come with an override functionality that is often overlooked but is, in fact, a critical piece of why these ABB drives can be an excellent choice for your application. The override mode is a significant built-in feature of the variable frequency drive (VFD) ACH580. The ACH580 makes the HVAC and smoke control systems more flexible and more robust during adverse conditions because of the override mode.
What is override mode? This feature makes HVAC products respond properly in emergency fire or life-safety situations. In the ABB ACH580, override mode allows the drive to run a motor at an adjustable, predefined or PID controlled speed in any direction to assist a building smoke control system during evacuation and firefighting once a fire occurs. This increases safety of the building’s occupants and minimizes fire damage and restoration costs.
In an emergency situation, when the drive receives a signal (a contact closure) from the building's fire alarm system, the drive enters override mode and ignores all other irrelevant inputs whether they be analog or digital, and serial communication signals as well as commands from the drive’s keypad.
When ACH580 is in override mode:
• The display of the control panel will show a message that the override is active.
• It will not be possible to change any of the VFD’s parameters.
• The HAND, OFF and AUTO keys on the control panel will be disabled.
• The impact of faults depends on their priority.
• Configured interlocks, if not satisfied, stop the motor when override is activated.
When in override mode, the VFD is programmed to ignore most of its trips and warnings that would normally stop the drive, ensuring maximum availability during the emergency.