Nate Nagel wrote:
I'm ASSuming that I already know the answer to this, but I'll try anyway
- assume a usual little surge protector with three MOVs, H-N, H-G, N-G.
Will it provide protection to a device connected directly by hard wires
to the receptacle that it's plugged into? I'm guessing that it really
doesn't care as to "upstream" or "downstream" only that the level of
protection depends somewhat on the distance from the protector. Also if
a surge destroys it it obviously will not disconnect a device not
"downstream" of it.

Reason I ask is, due to the fun and games I've been having with
repairing appliances due to a big surge about a week and a half ago, I
thought that adding surge protection to my furnace and air filter would
be a good idea. Problem is, now that I dig into it, the furnace is
hardwired to the back of a box on the side of the furnace. There is a
switch and a duplex receptacle in that box. The switch controls the
furnace and one half of the recep; the other is always hot. A
humidifier is plugged into the switched side, a condensate pump into the
unswitched side. I figured the best I could do, without adding some
kind of hardwired surge protection, was to plug it into the unswitched
recep for the condensate pump and it would provide the same protection
as if it were inline, with the caveat that if a surge destroyed the MOVs
in the surge protector, it is possible that it might zap the furnace
before the breaker tripped. Am I correct?

Are there any common, commercially available point of use surge
protectors designed to be mounted in, say, a 1900 box screwed to the
side of a piece of equipment? I am thinking that one at the dishwasher
might be advisable as well, as its only protection appears to be one H-N
MOV and we already established that that wasn't sufficient in at least
one instance

thanks,

nate

The problem with using a downstream surge protector for an upstream item is
that the inductance in the wiring between the upstream connection point and
the surge protector may keep the spike from being suppressed. The inductance
works to help suppress the spike for anything downstream of the surge protector.

I know there isn't much inductance in that short a piece of wire, but for
fast spikes it is an important part of the suppression system.

Bill