[TowerTalk] Whole house surge suppressor's

[Jim Thomson]

Date: Tue, 4 Jan 2011 03:02:53 -0800 (PST)
From: AI4WM Bill <ai4wm at yahoo.com>
Subject: Re: [TowerTalk] Whole house  surge suppressor's.
To: towertalk at contesting.com, Jim Thomson <jim.thom at telus.net>
Message-ID: <221129.8587.qm at web57905.mail.re3.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1

Jim,
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.

73,

Bill

AI4WM

##  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 use
 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