LED tape run length and driver sizing

Two things go wrong with LED tape more than anything else: undersized drivers and over-long runs. The driver sizing is arithmetic. Multiply watts per foot by the length, then add headroom. Twenty per cent is the usual minimum, because running a driver at its absolute rated limit shortens its life and leaves nothing for the inrush when the circuit energises.

Run length is a physical limit rather than a preference. Voltage drops along the tape itself, so the far end of a long run is dimmer than the near end, and beyond a certain length it becomes visible. Twenty-four volt tape typically tolerates roughly twice the run of twelve volt for the same drop, which is why most quality architectural tape is now twenty-four volt. The manufacturer publishes the real maximum for their product and it should always win over any rule of thumb.

If the run is too long, the fix is usually feeding it from both ends or splitting it into sections with their own home runs, rather than accepting the fade. And if the tape is dimmable, the driver must be dimmable too and must match the control protocol, whether that is 0-10V, forward phase, reverse phase or DALI. A dimmable tape on a non-dimming driver is a surprisingly common and entirely avoidable mistake.