Protection Features

The C-Bus Digital Dimmers incorporate multiple protection features to ensure safe, reliable operation. The conditions monitored by these features are made available for monitoring via C-Bus Measurement Application and/or the C-Bus Error Reporting Application, as well as via the front panel indicators.

Thermal Protection

Over-Temperature Wind-Back

If the load on the dimmer is too high for the environmental and loading conditions, and a dimmer channel temperature rises above 80 °C, the dimmer channel will automatically reduce its brightness to lower the operating temperature below 80 °C. Whilst the brightness is reduced, the condition will be indicated as an Over Temperature Wind-Back error condition, both via the front panel indicator for the affected channel (For details refer Channel Indicator) and via the C-Bus Error Reporting Application.

Once the Over Temperature Wind-Back condition is active, if the dimmer channel temperature returns below 80 °C, the operation will return to normal and the Over Temperature Wind-Back error condition will be cleared.

Note that where dimmer channels share a common heatsink, an overload on one channel may affect one or more adjacent channels.

Over-Temperature Shutdown

In the Over Temperature Wind-Back condition, if the dimmer channel temperature continues to rise and reaches 100 °C, the dimmer channel will shut down to protect the unit, and the Over Temperature Shutdown error condition will be indicated.

Once the over temperature shutdown error condition is triggered, the channel has to be turned off and on again from C-Bus or the front panel, to clear the error and try to restart.

Thermal Fuses

The Unit Power Supply, as well as each Dimming Bank (for 5508D1D and 5504D2D) or Dimmer Channel (5504DHD only) has a thermal fuse which is required for safety certification. These fuses have a trip temperature well in excess of any temperature that would occur in normal circumstances and will only trip in the event of a serious malfunction or other external source of heat. If these fuses trip, the unit will need to be replaced.

Overcurrent Protection

Each dimmer channel monitors for overcurrent conditions on a cycle by cycle basis. If the current flowing in the load is too high, the channel will switch off within a fraction of a millisecond, to protect the dimmer channel.

For the 5508D1D and 5504D2D, this limit is approximately 10 A, whereas for the 5504DHD the limit is approximately 40 A. This means that the 5504DHD High Power Dimmer is more tolerant of loads with high inrush such as LED Strip Drivers.

During startup, short term overcurrent conditions can be normal, (example, the cold-filament inrush with an incandescent lamp, or the initial inrush of a dimmable LED strip driver). The dimmer firmware allows for this and automatically performs a certain number of restarts, however if the overcurrent condition persists for too long, the channel will shut down and indicate an Overcurrent condition, both via the front panel indicator for the affected channel (For details refer Channel Indicator) and via the C-Bus Error Reporting Application. If an overcurrent condition is triggered, the channel has to be turned off and on again from C-Bus or the front panel, to clear the error and try to restart.

Incompatible Load

If the dimmer channel identifies that the connected load is incompatible with the selected mode or load profile, the channel will turn off and indicate Incompatible Load Error via the channel indicator. This can often be corrected by configuring a custom load profile with a lower maximum conduction time (for details refer Load Profiles).

Mode Error

In TE mode, if inductive spikes are observed while dimming (suggesting a presence of an inductive load), the channel will shut down and indicate mode error. If this occurs, channels with inductive loads must be changed to LE mode. If this error condition occurs on channels with other load types, it may be due to excessive inductance in the external supply connection, such as an isolation transformer, or ripple filter.

NOTE: When operating a channel in LE mode with an electronic (capacitive) load, the losses are significantly increased, meaning that the rating is significantly lower. Refer to the rating table in Compatible Loads.