Benefits of override mode for VSDs in buildings
Benefits of override mode for VSDs in buildings
Override mode is a function that helps engineers designing escape routes in the event of building fires. It also allows emergency services to easily trigger these essential functions to aid in the evacuation of residents or whilst fighting fires.
Large buildings and other public facilities need sophisticated heating, ventilation and air conditioning systems. It is critical for controlling the indoor microclimate not just in everyday use but in extreme situations including fire.
ABB HVAC drives bring enormous benefits to all types of buildings, yet many of these benefits are not widely recognized. The result is that end-users can be missing out on considerable cost and time savings, but most importantly, life and property safety. One example of a built-in feature of the ACH580 VSD is the provision of the safety override mode.
Override mode (sometimes called fireman’s override mode) is a feature enabling ABB HVAC drives products to respond in a particular way to fire/life-safety situations. The override mode in the ACH580 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. The feature increases safety for a building’s occupants. It can also minimise fire damage and restoration costs.
Override Mode
The override mode is usually triggered with a special key at the firefighter’s control station. Upon receipt of a signal from a contact within the building’s fire alarm system, the drive enters override mode and ignores all other irrelevant inputs. This includes analogue and digital inputs, serial communication signals, and commands from the drive’s keypad.
The drive may be programmed to ignore or reset faults to ensure a “run at all costs” operation. Override mode cannot be triggered by any other signal: once override mode is activated, the drive cannot exit this mode until the fire condition input signal is reset, or power removed from the drive.
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