On Apr 18, 3:00 pm, "John Gilmer" wrote:
That means that you regular old circuit breaker in you main panel will
"protect" the MOV from thermal runaway. Trouble is that once the CB trips
you lose protection until to notice the open breaker.

One would think that "someone" would make a MOV equiped device with a
self-resetting thermal breaker as part of the design. ALL of them seem to
have either fuxes or the MOV self-destructs in a way that doesn't set the
device on fire or create a short.

If the MOV got that 'hot' as to open a thermal fuse, it was grossly
undersized – operating in complete violation of its manufacturer.
Grossly undersizing is common with plug-in protectors since profit
margins are more important than effective protection. MOVs much shunt
(clamp, divert, connect) surges to earth AND remain *functional*.
Those promoting plug-in protectors forget to mention that a protector
must not fail by blowing the thermal fuse.

Any MOV that gets so hot as to trip a thermal fuse was violating MOV
manufacturer specs and providing no effective protection. The only
acceptable MOV failure means no excessive heat - no MOV vaporization.
But such failures get the naive to recommend more protectors -
increase sales. Again, which is more important – profits or
protection?

Scary pictures demonstrate problem with grossly undersized
protectors that still have UL 1449 approval. Not only do we instead
install one properly sized 'whole house' protector. We also do not
want protectors located on a rug or adjacent to a pile of desktop
papers. The scary pictures demonstrate a 'too common' problem with
plug-in protectors that Bud promotes for:
http://www.hanford.gov/rl/?page=556&parent=554
http://www.westwhitelandfire.com/Art...Protectors.pdf
http://www.ddxg.net/old/surge_protectors.htm
http://www.zerosurge.com/HTML/movs.html
http://tinyurl.com/3x73ol http://www3.cw56.com/news/articles/local/BO63312/