MOVs normally fail in thermal runaway and low resistance. All surge
suppressors (US) should be listed under UL1449. UL1449 requires
overheating MOVs be disconnected by a thermal disconnect.

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.


Carefully follow the manufacturer’s instructions. Keeping connecting wires
short is very important.

Well, it takes te impulse a little more than a nano-second to travel a foot.
If the response time of the MOV is measured in micro or even mili seconds,
the length of the wiring just doesn't make any difference.


Everything I saw at the Intermatic site indicated that their service panel
suppressors were MOV based.

I didn’t see anything at lightningprotectioncor.com on why their
suppressors would be superior.

Equipment most likely to be damaged has connection to both power and
signal (phone, cable).

Amen!

If a strong surge produces a 1000A current to earth, and the resistance to
earth is a very good 10 ohms, the voltage at the service ‘ground’ will
rise to 10,000V above ‘absolute ground’. The way to protect equipment is
to keep the ground reference for power and phone and cable at the same
potential.

Yep!

That requires a *short* ‘ground’ wire from phone and cable entry protectors
to the ‘ground’ at the power service.

That's why all utility wires are supposed to come into the house at the same
general location so that the grounds can be bonded together. The "cable
folks" often don't bother. Ditto for the "dish" folks.



With adequate ratings, using service panel suppressors, and plug-in
suppressors on “sensitive” electronics with power and signal connections,
you can protect against almost all lightning (not including a direct
strike to the house - very uncommon).

Well, you can get "local" break out boxes that will protect AC plugs and 1
or 2 coax and/or 1 or 2 phone lines. If the grounds are bonded well at
the electric service grounds I suspect that your local suppressor may have a
shorter than expected life.

If using a plug-in suppressor, all wiring (power, phone, cable, ...) going
to a set of protected equipment must go through the suppressor.

AMEN!
--
bud--


** Posted from http://www.teranews.com **