The master relay coil in this model is de-energized when conditions are normal.
Upon phase loss or phase unbalance (12% or more) the master relay will energize after the time delay has elapsed (standard 1 ½ seconds).
The master relay will not react to a total power interruption of any duration.
The PND model will automatically reset when fault has been corrected and balanced voltage is restored.
Model PND includes led indicators for normal (green) and phase loss (yellow) as a standard feature. It also includes DPDT output relay with 30 amp contact rating.
A total power loss will not affect the model PND since the master relay is normally de-energized. This characteristic helps eliminate the possibility of nuisance tripping during storms and other outages.
The PND model is recommended for applications involving a main breaker or bolted pressure switch which must be manually reset after an outage occurs.