[Amps] MOVs

[John Lyles]

I have had a pair of large Harris MOVs across my main panel to neutral 
and line to line, for 21 years now. They are fed through a
double pole breaker and there is a relay that fires a sonarlert if the 
breaker trips. We get some great lightning locally during
summer monsoon season, and I haven't had any equipment failures that I 
know about. Only once has the breaker tripped. I knew it when I came 
home from work, the sonalert was sounding.

If they do fail open, then I would stand to be unprotected.

Professionally, I use more Transorbs (from companies like OnSemi and 
Microsemi). They are superior to back to back zeners for transient spike 
clamping.

73
John
K5PRO



> Message: 5
> Date: Sat, 25 Jan 2014 04:43:23 -0800
> From: "Jim Thomson" <jim.thom at telus.net>
> To: <amps at contesting.com>
> Subject: [Amps] MOVs
> Message-ID: <5ADE14C0E8F14EA392909F4C98133279 at JimPC>
> Content-Type: text/plain;	charset="utf-8"
>
> Date: Thu, 23 Jan 2014 22:31:53 -0800
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: amps at contesting.com
> Subject: Re: [Amps] MOVs
>
> On 1/23/2014 7:18 AM, Paul Baldock wrote:
>> If the amp is running off 240V where in the USA this is symmetrical
>> about ground and then the MOV is placed between the two phases, it
>> seems to me that there would not be a surge current to ground.
>
> Right.  The problem comes when you take the MOV to the ground.
>
> 73, Jim K9YC
>
>
> ##  On whole house protectors, they use a pair of huge, FUSED
> 130 V rated movs.... wired from each hot side to the neutral...which of
> course is also grounded.   So you end up with 2 x movs, nose to tail, in series
> across the 240 V line..with the junction point bonded to neutral + ground.

> ##  On paper, it should work.  Ideally the best way would be to use the whole house protector scheme
> right at the main 200A  panel.  Then the entire 200A panel is protected from transients  coming down the
> drop wire into the home.  It should also kill transients + spikes   from any equipment  on any branch lines...
> like electric motors etc.   But then again, the electric motor, etc could be a loooong way from the main panel
> movs.
>
> ##  On paper, using  MOVS  at the 200A main panel  AND the equipment, line to neutral  and not line to ground  at the
> equipment end...  should work.   IF  movs are not fused..you are asking for trouble.   Real simple to fuse em..plus add
> a neon or led on the output side of the fuse to serve as a visual indicator that the fuse is functional..... which of course
> also means the mov is functional.
>
> ##  I will defer to Jim Brown as to his thoughts  of using movs wired  from hot to neutral at the equipment end of things.
> Another thought is to wire all ham gear for 240 vac use if possible..including xcvrs etc..but that is not always possible.
>
> Jim   VE7RF
>