We seem to have a number of occurrences of major voltage reduction, over extended periods.

An example was a period of at least 10 hours where line voltage measured at 187V, against the standard delivery of 220V.

The aircon systems (single phase) in my home couldn't even muster enough muscle to turn the evap fan properly, let alone the compressor.

I am looking for a cost-effective, simple way to shut down a heat-pump, or aircon system, when line voltage goes below an acceptable threshold & then either auto-set when it returns to the acceptable value, or have to be manually reset.

Thanks so much for your input.