In , on 07/21/03
at 11:36 AM, (Foo Man Choo SE) said:

[ ... ]

Assuming I have my earth grounding checked out and get a whole house
protection system installed, can I get rid of the local MOV-based
surge suppressors which, presumably, didn't do me any good to begin
with. (I have some 3000 joule rated ones bought at Lowe's for about
$40.)

$40.00 is the point where surge suppressors become effective.

Or, is there some benefit to keeping these connected? What
about the theory that they might help in increasing the life of
circuit board components by eliminating the hundreds of small surges
occurring throughout the day which may be taking their toll on
electronic components?

It's a matter of degree. The equipment's own power supply should be
able to deal with "small" transients, but at some point the unit will
be overwhelmed. This is also true for the MOV. An enormous number of
small transients can be safely handled, at least a few large
transients, but only one really big one. I realize this is not very
precise, but the details depend on the suppressor's design and your
brand of transient.

Also, most of these surge suppressors offer some sort of lifetime
equipment damage warranty. Wonder if anyone has actually won a claim
from them? I've heard that this is mostly a scam since it would be
next to impossible to verify. For example, how can you really prove
that the damaged equipment was really plugged into the suppressor at
the time of damage? If it was easy, it would also be easy to fake it
and blame the surge suppressor to get the equipment replaced free of
cost. One of the requirements on the one from Lowe's is that the
surge suppressor also be damaged along with the equipment it is
"protecting".

I also wonder about these claims, but I have no first or second hand
experience with these issues.

Now, it's interesting that two of my power adaptors
(for laptops) were zapped out of service but the Radio Shack surge
suppressors were still working (at least the light was still on).
Could be that the MOV's were made ineffective but power was still
being let through.

Remember that the MOV ususlly fails "open" (meaning that, while it
looks OK, it is not a functioning protective device). It is not
practical to test MOV's in the field. (Don't take this analogy too far,
but it's somewhat like testing a match.) That light in the Radio Shack
units simply tells you that power is available, not that there is any
protection.

I've seen some units that have a fuse for the MOV. While this might
offer a small amount of protection for the MOV, the point is that once
the MOV's fuse blows, your equipment is not protected. In effect the
"suppressor" us using your equipment to protect it's MOV.

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