Date: Tue, 4 Jan 2011 03:02:53 -0800 (PST)
From: AI4WM Bill <firstname.lastname@example.org>
Subject: Re: [TowerTalk] Whole house surge suppressor's.
To: email@example.com, Jim Thomson <firstname.lastname@example.org>
Content-Type: text/plain; charset=iso-8859-1
I agree with your statement about most consumer grade surge protectors.? Many
cannot handle arc flash and the tremendous amount of energy from a strike.?
Then many that could are not installed to correctly dissipate what they should.
Where I live FPL supplies whole house protection at the meter for a small
monthly fee and they will pay for damage up to a given amount should their
After working in commercial radio and seeing the protection used as well as
what PP&L used when I lived in PA I cringe at much of the chinese junk being
sold as protection. Also as a former fire fighter I am very surprised we did
not and do not see more fires caused by the cheap junk out there.
## what baffles me is most of these plastic encased ' whole house
protector's' you see at home depot, etc, all say to use a spare 40-60A
2-pole breaker in your main panel ! The Joslyn commercial grade units all
a 20A-600 V rated cartridge fuse... one per hockey puck size mov..inside the
nema rated fireproof box. I don't see the requirement for a 40-60A breaker
for small size movs. That's just asking for trbl....no wonder they burst
into flames. They should be using an internal fuse in the protection box...and
not oversized breaker's.
## The standard deal for the commercial grade joslyn units is just two big
puck size movs.... and each mov is wired from each hot to neutral. The main
200A panel will have it's neutral and GRND bonded together... which by
code... is the ONLY place you can bond the neutral and grnd together... via an
internal cu strap. IF a sub panel is used... then the sub panel will NOT
have it's neutral and grnd internally bonded. Reason is... in any sub
pane, all fault current must travel from sub panel back to main 200A panel...
via the grnd wire... and NOT the neutral.
## By wiring each MOV in the joslyn arrestors from each hot to
neutral.......... what u really have when u re-draw it is..... you have 2 x
movs nose to tail across the 240 line... with the center tap junction of the 2
x mov's grnded. Then you are protected from transients from each hot leg to
neutral/grnd..and also across the 2 x hot legs.
Notice in the mouser catalog... these new small quarter /nickel size movs...
all have 3 x leads on them these days. The new style mov's have an internal
fuse built into them. The 3rd wire is what runs the led, etc..and tell's you
that the mov is good ..or not. The 3rd wire on these new style mov's is
slightly offset to one side. Reason is..so they can only be inserted into
the mating PC board one way.
If the whole house protector is of the right type..and wired correctly, you
probably don't require down stream mov's at all. The 3 x way protection that
you see in the arrl handbook uses 3 x movs H-N , H-G and N-G . Whether
all 3 x movs are required..or just the H-N is debatable. Whether 1 or 3 x
movs used, at least either install 1/3 correct size fuses so you don't
create a fire..... or better yet, use the new style movs with the built in
fuse. The mov's with the built in fuse have another advantage.... they
can't be overfused... or RE-fused. Internal fuse blows, the mov is no longer
in the circuit..and no chance of future mov explosions/fires. You also don't
have any protection.
later.. Jim VE7RF
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