Harmonics are cumulative on the neutral bus bar, hence the total load is the result of the number of electronic devices (i.e. non-linear loads) running at the same time.
Our filters are installed on the neutral, hence we cannot solve a harmonics problem within a delta-wired circuit, however if that delta-wired branch-circuit is fed from a distribution panel with a harmonic filter, the equipment will still benefit from getting clean 60-Hz power.
Since these filters are a passive device, not subject to any wear and tear, the only critical issue is that it should be installed right. For all practical purposes these filters last forever unless the circuit takes a direct lightning hit or the building burns down.
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