Effect Of Ageing On Lamps - ABB i-bus KNX Product Manual

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ABB i-bus KNX
Planning and application
4.5

Effect of ageing on lamps

Every fluorescent lamp ages in service. The lighting power of the fluorescent lamps degrades, i.e. a lower
brightness is produced at the same control value. This can even mean that the setpoint originally required
can no longer be achieved with maximum control. For this reason, the lighting is to be dimensioned, so
that the required setpoint brightness can be achieved until the luminaires are routinely exchanged.
In principle, the ageing luminaires have no effect on the control circuit. If a lower brightness level is
achieved due to ageing of the luminaires with the same control, the DLR/A, e.g. via a DLR/A lighting
group, will continue to increase the level of artificial lighting until the setpoint brightness is achieved.
However, it must be considered that the characteristic of the luminaires change with ageing. The
characteristic has been determined during the calibration procedure and is the basis for the control
algorithm. In this way, it is possible that light control discrepancies result.
The following approach results
The recorded characteristic of the artificial lighting is calculated with the control value. Assuming that the
lamp generated 30 % less light, the value of the characteristic would be 1.33 times larger than the real
value.
The DLR/A then assumes that the level of daylight is lower than it actually is. There appears to be less
daylight available and compensation is necessary.
With a compensation factor of 30 (for the control algorithm 0.3), an approximate reduction of the setpoint
value by 10 % would be achieved. The DLR/A would control to a level, which is too dark by 10 %.
In concrete terms that would mean that a light control originally set by the DLR/A to 500 lx will now only
provide a brightness value of 450 lx. Furthermore, the tolerances apply as described in the chapter
Technical data DLR/A
Note
The burn-in time, where the light may not be dimmed, must be complied with to ensure that the most
stable possible luminaire performance is assured. During the burn-in time, which usually lasts between
50 and 100 hours, the luminaires must be operated at 100 % brightness.
The burn-in time of a luminaire can be obtained from the manufacturer.
160 2CDC507128D0202 | DLR/A 4.8.1.1
4.8.1.1, page 12, of the DALI Light Controller.