A fuse that blows inside a protector only disconnects the
protector from AC mains. It leaves the appliance fully
connected. This was all but required by UL1449 2nd edition
when so many protectors failed catastrophically and spit
flames. Tests for two separate articles in 1980s PC Magazine
even noted the problem.

Today protectors are a less of a fire hazards due to UL1449
2nd edition. We had a UL1449 protector spit flames once. It
was on linoleum tile. The last place a protector (or the
mains circuit breakers) need be located is among combustible
material. We enclose circuit breakers for the same reason.
Breakers also never spit sparks, except .... When was the
last time your rug caught fire due to an extension cord. And
yet that fire also is now considered so dangerous that Arc
Fault breakers are required. Last place I want an undersize
protector (which means plug-in protector) is where a protector
failure can cause a fire.

In the meantime, a microsecond (and destructive) transient
has already damaged electronics while in-line fuses take
milliseconds to blow? There is no inline fuses on plug-in
protectors to disconnect the appliance. Furthermore fuses
don't protect from transients.

Fuses disconnect damaged electronics from the AC mains for
human safety - so the house does not burn down. That is also
the function of a fuse on surge protector circuits. Fuse
disconnects a vaporized or shorted protector; while appliance
remains fully connected and exposed to the transient. Fuse
only disconnects the MOV - not the appliance. (This MOV fuse
should not be confused with the larger 15 amp breaker.)

A plug-in protector puts no fuses in series with the load.
And those inductors? Application notes from MOV manufacturers
recommend those inductors only to protect the MOVs. Smaller
MOV then can withstand slightly more energy. Those inductors
are ... well again the numbers ... are insufficient inductance
as load protection. Furthermore, an electronic appliance
already has a superior line filter inside its power supply -
to meet FCC requirements. The inductor in a power strip
protector - if it even exists - is not for appliance
protection.

Previously cited was a damaged TV and stereo; and an
undamaged damaged computer. Assumed was that all had equal
internal protection. The TV need only meet the 600 volt
standard (posted previously). Computer power supplies must
withstand voltages in excess of 1000 volts - as even demanded
by Intel specs. So a transient large enough to overwhelm 600
volt protection inside a TV could not overwhelm the 1000 volt
protection in a computer power supply. Where does that
damage prove a computer protector with too few joules did
anything? It does not. And again, with or without the
plug-in protector, the computer was connected directly to AC
mains. More likely, the computer protected itself.

BTW, also mentioned was a grounded receptacle. No earth
ground exists at that wall receptacle. Wire impedance (and
other electrical concepts) means a receptacle has all but no
earth ground. Another critical expression was posted that
examples the concept - 'less than 10 foot' connection to earth
ground. Wire distance and other factors inside wall wires
conspire to make that receptacle safety ground not an earth
ground. No earth ground is why plug-in protectors are not
effective.

I can appreciate why you might think the plug-in protector
effective. But principles of junior high school science
apply. A fact must be proven both theoretically and
experimentally. Your example contradicts well proven theory.
And numbers for internal appliance protection explain why one
appliance may be damaged while the other not damaged. You
example does not demonstrate the plug-in protector did
anything effective.

From that FL (Hurricane Andrew) example, thousands of volts
on a 120 volt AC line will damage appliances whether off or
on. Switches (and fuses) are only rated for hundreds of
volts. Thousands of voltage would have passed through those
open switches (and fuses). Many appliances (ie computers and
remote controlled TVs) have power always applied. He had no
appliance damage - not even a clock - according to the sales
brochure. That protector was rated at 1200 joules. To be
equivalent, a plug-in protector would need be rated at 2400 to
3600 joules.

No that FL protector was operating well beyond what even
'whole house' protectors are designed to do. It was
blackened. That is all I remember about the protector. I
don't even remember if his Mains breaker tripped. But a
protector designed to withstand 300 'same sized transients'
did accomplish what the plug-in '2 transient' (undersized)
protector obviously could not. A protector rated for 150
times more 'same sized transients' could accomplish the
protection - albeit destructively. Those grossly undersized
plug-in protectors would have only protected themselves. To
meet UL1449, grossly undersized plug-in protectors must
quickly disconnect MOV protector circuits - abandoning the
appliance to protect itself.

In the meantime, protectors are for destructive transients
that occur in microseconds - transistor protection. Fuses and
circuit breakers are for milliseconds events and longer -
human protection. Transistor protection means the protector
is only as effective as its earth ground which is why one
'whole house' protector is so effective.

In the meantime, none of this would solve or address the
strange light flickering.

Choreboy wrote:
w_tom wrote:
The plug-in protector does nothing effective. A properly
sized protector should not vaporize or opens when shunting
typically destructive transients. If protector is vaporized,
then it provided ineffective protection.

As it vaporizes it should blow the fuse device.
...

It's the whole-house protector that is parallel to the load, like a
light bulb. a plug-in protector should put at least two inductors and
two fuse devices in series with the load.
...

Too little got through the protector to damage the TV.
...

AFAIK, I've never had a plug-in protector damaged. My neighbors wiped
one out because their phone ground isn't bonded to their power ground.

I installed my whole-house protector 20 years ago and don't remember the
specs. I suppose it clamps at something like 300 volts. It would do
nothing to a transient up to 300 volts from ground. The transformer
that powers digital equipment responds to the derivative of input
current. The fast rise time of a transient could send a big spike
through the transformer even if the transient is less than 300 volts. A
plug-in surge protector blocks transients with inductors.
...

I know it did not save my tv and my stereo. As they were plugged into
an ungrounded outlet and the antenna was rabbit ears and there was no
ground nearby, I know the electrical path was between the hot and the
neutral. Why would I want to replace all electrical components?

The cause was the breaking of a distant power line in an ice storm.
Therefore, the surge must have affected the input of the street
transformer and both sides of the output. Clearly, the plug-in
protector saved my computer equipment from the same fate as my TV
and stereo.
...

How often do plug-in protectors cause fires? UL seems to find
them safe.

Intermatic once provided a brochure describing an event in
their sales manager's house when Andrew went through Florida.
High voltage primary wire dropped on a wire into his house.
Intermatic 'whole house' protector was badly burned. But it
shunted the high voltage primary voltage until a utility fuse
finally cut off those thousands of volts. Nothing inside his
house was damaged. The house did not catch fire from
thousands of volts on 120 volt appliances.

How many joules do you think the protector absorbed? Did any of his
breakers kick? What equipment in his house was running? Did he have
any plug-in protectors? Was his whole-house protector still okay?