Caesar Romano wrote:
If two surge protectors are connected in series, is the amount of
surge protection available at the down-stream protector approximately
equal to the sum of the two individual protections??

I haven't thought of it that way. I suppose it's possible, depending on
how a particular protector circuit functions.

I have a protector at my service entrance. When lightning struck my
house, I had perhaps $1000 worth of damage to electronics in various
rooms, but none to my my computer/telephone equipment, which was on a
plug-in protector. Because the surge didn't come in on the line, it
made a big difference to have that equipment plugged directly into a
protector. It's possible that my computer would have been wrecked if
the whole-house protector hadn't absorbed some of the energy.

I have twelve items plugged in at my computer desk. A surge protector
is plugged in at the wall. That feeds a lamp, the phone, and another
surge protector.

The second protector feeds my computer stuff and a third protector,
which feeds my audio/video stuff. If the a/v stuff were connected to a
cable or outdoor antenna, this might be unwise.

One reason to use three protectors is to be able to leave my computer
stuff and my audio stuff switched off, for added protection, while still
using my phone and lamp. The second protector could save my computer
stuff in the event that the first protector fails and lets something
through.