"Scott Dorsey" wrote in message

Arny Krueger wrote:
"GregS" wrote in message

The big RF coils also slow down the spikes so the
MOV's work better.

It's true that MOVs respond in about 100 nanoseconds,
but by most accounts thats a bit of overkill. A 200
nanosecond spike can't have much energy in it unless its
peak voltage is astronomical. In 200 nanoseconds, a
typical inductive kick from a power transformer (your
earlier example) hasn't built up very far...

Right, but the induced lightning is what is really scary,
and that is a very fast risetime pulse that really does
behave like RF.

Agreed.

Most of the solutions to dealing with
that have to do with making low-pass filters (like those
big chokes, or even a few wraps of the service entry
cable), in order to convince the spike either to take a
different path to ground or to smooth it out so that MOVs
and gas tubes can effectively clamp it.

Interestingly enough, GE (the origional MOV developers)
argue that MOV's have enough inherent capacitance to handle
*any* quick risetime signal.

You need to be thinking about RF, not about DC.

If you go back to the post that started this portion of the
discussion, we were talking about transients that are likely
to be generated inside the house, not lightening. Transients
from other standard electrical appliances, audio or
otherwise are the context.

We've also agreed that for openers, whole-house surge
supression should be installed wherever damage from external
surges sources like lightening is an issue.

While this subthread hasn't exactly covered the issue of
protecting structures from lightening that strikes them, (as
opposed to strikes on or near a power line) I think that
Scott you've posted some agreeable advice about that as
well.