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[TowerTalk] Whole house surge suppressor's

To: <>
Subject: [TowerTalk] Whole house surge suppressor's
From: "Jim Thomson" <>
Date: Tue, 4 Jan 2011 06:30:30 -0800
List-post: <">>
Date: Tue, 4 Jan 2011 03:02:53 -0800 (PST)
From: AI4WM Bill <>
Subject: Re: [TowerTalk] Whole house  surge suppressor's.
To:, Jim Thomson <>
Message-ID: <>
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 
protectors fail.

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 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 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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