Originally Posted by Vern
Neither of them, one of whom is a good friend, reported any adverse after-effect. Apparently no damage was done.
Because reverse polarity does not damage any appliances.
To have reverse polarity, wires must be fully reversed. Design that Progressive must use to detect reverse polarity can also report other anomalies (as described earlier). None involved or should be confused with a completely different anomaly - an open ground.
BTW, ground is another human safety layer and also not for protecting appliances.