I've been in the fire service for 27 years now and I can't tell you the
number of surge suppressors of the type that are typically installed on
a 1/2" or 3/4' knockout hole*http://tinyurl.com/2cpxn7a *that created
the structure fire that we were responding to. On a couple of
occasions, I've seen them violently shoot green flames out of them in
every direction as they burned themselves to a cinder.
My power company installs the meter base style suppressor which places
it outside of the structure the majority of the time. I'm sure that's
probably what you're also looking at.
Jon Pearl - W4ABC
## The Joslyn brand surge protector's are used by the 10's of thousands by
telco's across NA.
They are mounted below, or close by a main panel. Conduit between main panel
The protector's we used at work, were all in steel enclosures, and those
things were latched
shut tighter than a drum. Each of the two [ 3 movs used for 3 phase] huge
movs are wired
between hot and neutral [ ditto with 3 -phase]. Each mov had a 20A slow blow
fuse in front of it.
[600V rated... big cartridge fuses.. like the .375" to .5" x 2" long variety]
Output of each fuse feeds a neon. Output of neon wired to same neutral. A
4pdt relay..with a 120 vac coil
is also used... one per mov. 120 vac coil wired between output of fuse and
## OK, with everything normal, all the neons are lit green. If one or more
MOV's shorts out, the mating fuse
that feeds it blows open asap, and MOV is now out of the circuit. Associated
neon also goes dark. Mating
120 vac dpdt relay also drops out..... bringing in an alarm to the alarm
center/NOC etc. All the relay's of course,
in normal operation, are always operated 24/7..... except when a mov fuse blows
## I never saw one of those joslyn protector's ever catch fire in 34 yrs I
was there. [ no equipment failures from
lightning, transients/spikes/surges either]. As long as they are fused
I don't see how the mov could burst into flames. Even if it did, none of it
would get past the steel box. Those box's
were sealed very good, with a pair of real heavy duty latchs. They were not
like a regular steel electrical box either.
These things were water proof, fire rated nema box's. The seal design was
the best yet. If they were the slightest fire hazard,
the insurance co would have been reading us the riot act. [ factory mutual in
the US is the main insurance co for most of the telco's
in the usa + canada.] In some parts of Florida, etc, home insurance co's will
insist that whole house protector's are employed.
Insurance co's were getting tired of paying out claims in lightning prone
## I have seen some of the whole house protector's..sold at home depot etc..
that use way smaller mov's.... and contain
no internal fuses... but use a spare 40-60A breaker position on the main
panel. The box's they use look flaky to me. They also
use plane romex, etc, from main panel to plastic box... and no conduit.
Later... Jim VE7RF
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