pianotuna wrote:
MOV fall on their sword to protect the devices down stream.
MOV manufacturers are quite blunt about it. MOVs do not do protection when failing. Worse, they create a serious human safety issue. However if a protector is grossly undersized (does no effective protection) and it fails, then naive consumers recommend it and buy more.
An effective MOV protector remains functional even after direct lightning strikes.
But that is not the anomaly that RV protectors are designed to protect from. The word surge describes so many completely different and unrelated anomalies. For example, does it protect from a tidal surge? Obviously not. Does it protect from low DC voltages inside a computer's motherboard? Obviously it does not protect from that surge. Does it protect from a brownout? Well a Progressive does. Those completely different devices, called surge protector and located inside a house, do not.
In each case, an anomaly must be defined long before discussing some box called a surge protector. Since no surge protector protects from a surge on the stock market.
A Progressive protects from anomalies so often found in campgrounds including a brownout, reverse polarity, missing safety ground (which is not an earth ground), or floating neutral. All these are a threat mostly to motorized appliances or humans. Other anomalies (frequency variation, harmonics, missing earth ground, EMI/EMC, bad power factor, blackout, RFI, etc) are completely ignored.
Protection from transients (ie lightning) means the protector must be as close to earth ground as possible. Only the 'moutned to the pole' protectors are effective for that anomaly. And since that anomaly is quite rare (maybe once every ten years), then many RV protectors ignore that less frequent threat.
Effective protection from transients (due to lightning, utility switching, linemen errors, tree rodents, and wind) means MOVs do not fail. And must make a low impedance connection to earth ground. If mounted inside the RV, then a low impedance connection does not exist.
Discussion of each protector must first defined each and the many different anomalies that are relevant. Described are the anomalies of most concern in campgrounds. Those are unrelated to other anomalies (ie surges) that are a concern in homes.
