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Pete C.

HeyBub wrote:

wrote:
On Apr 17, 3:50 pm, "HeyBub" wrote:
Robert11 wrote:
Hello,

Having a new service box installed in a residence.

Electrician has never used these before, so thought I'd ask here.

Was thinking of purchasing, and having him install, an Intermatic
Whole House Surge Suppressor
Model 4870 in the new box. Have had several large lightning storms
in the past, and one nearby strike fried the control board on our
furnace ! The Intermatic unit isn't all that expensive, about $80
or so.
Any of you folks ever used this model ?

Worth doing ? Thoughts on ?

BTW: If they do ever take a big hit, do they (usually) fail open or
closed ?

e.g., would the MOV's be shorting the hot to neutral/ground after a
big hit, such that the unit would have to be removed prior to
re-initiating service ?

Intermatic surge protectors do not use MOVs - they are electronic.

What is this claim based on? If they don't use MOV's what exactly
do they use? Also, this would seem to imply that MOV's are not
considered electronic components, but I believe by any reasonable
definition, they are electronic components.

You're right, of course. MOV are classified as "electronic" components. But
metallic-oxide-varistors work like reverse fuses: they short their terminals
together. And, like fuses, they (usually) only work once with no indication
(other than sometimes smoke) that they won't work again.

MOVs will continue to work indefinitely if their rated clamping current
isn't exceeded, so they will readily clamp on the modest surges seen
every day. The mega surges from a really close lightning strike or a
tree branch dropping the primaries into the secondaries is what will
cause the MOV to self destruct and usually trip the circuit breaker in
the process thereby sacrificing itself to save the stuff downstream of
it.