When an MOV protector fails catastrophically, then it was
grossly undersized. It operated in a region not defined by
its manufacturer - in violation of the part's intent. But if
a power strip protector is undersized, then the homeowner will
know of the surge. That promotes more sales of undersized
protectors that really don't provide the protection and, as
Rob Mills demonstrates, can even create a house fire.

The effective protector earths a surge; and the homeowner
never knows it happened.

Protectors that provides effective protection are located
close to earth ground AND are properly sized. This is called
a 'whole house' protector. Where it is located? Not on a
pile of papers on a desk, or behind the furniture, on a rug,
or within dust balls. Just more reasons why plug-in
protectors (that cost so much money) are so ineffective.

Rob Mills wrote:
Don't have a whole house protector but think it's a good idea. I
do use those strip surge protectors on just about everything.
One time I had two in series and we caught a powerline overload
and the first protector basically exploded, burned the carpet
it was sitting on but a police scanner, shortwave radio and tel
answering machine connected to it survived. The second surge
protector which had a computer and printer hooked to it went
untouched.
These were standard "metal cased" MOV (metal oxide varistor) 5
outlet surge protectors. I'm convinced we would have had a
house fire if the surge protectors had been encased in a
plastic rather than metal. RM ~