On 1/26/2014 1:05 AM, John Lyles wrote:
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.
It happens, but usually when they take a hit that exceeds their capacity
by a substantial amount. IE: enough to blow them apart
It's far from the normal mode of failure which would be a short.
73
Roger (K8RI)
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@telus.net>
To: <amps@contesting.com>
Subject: [Amps] MOVs
Message-ID: <5ADE14C0E8F14EA392909F4C98133279@JimPC>
Content-Type: text/plain; charset="utf-8"
Date: Thu, 23 Jan 2014 22:31:53 -0800
From: Jim Brown <jim@audiosystemsgroup.com>
To: amps@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
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