Jim, is there a preferred way to extend the number of outlets from one of
the Brickwall surge protector? For example could an existing ISOBAR be
used? And, would it be advisable to remove the MOV's in the ISOBAR? I'm
presuming that every 120V outlet in the shack that has any interconnected
equipment should all be power from one branch circuit. Or perhaps, a second
Brickwall could be used on a second branch circuit.
How about protecting 240V circuits? That would seem necessary as well for
240V equipment (amps) interconnected with 120V equipment.
The computer network in the shack is a wireless repeater/bridge with short
CAT5 to the computers and powered on the same 120V branch as the rest of the
shack. OK?
---
Chuck, AE4CW
-----Original Message-----
From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of
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Sent: Monday, September 17, 2012 12:00 PM
To: rfi@contesting.com
Subject: RFI Digest, Vol 116, Issue 19
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Today's Topics:
1. Re: ISOBAR (Jim Brown)
2. Re: ISOBAR (Jim Brown)
3. Re: ISOBAR (Pete Smith N4ZR)
4. Re: ISOBAR (Pete Smith N4ZR)
----------------------------------------------------------------------
Message: 1
Date: Sun, 16 Sep 2012 10:12:57 -0700
From: Jim Brown <jim@audiosystemsgroup.com>
To: rfi@contesting.com
Subject: Re: [RFI] ISOBAR
Message-ID: <50560899.9090509@audiosystemsgroup.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 9/16/2012 2:22 AM, Christopher Brown wrote:
>
> On 9/15/12 5:46 PM, Jim Brown wrote:
>> I can't comment about RF filtering, but it's an MOV box, which is BAD
>> NEWS on a branch circuit.
> Care to explain or provide a ref?
The fundamental problem is that MOVs, like all shunt protectors, attempt to
short out the surge, mostly by conducting it to ground. When the MOV is at
the end of a branch circuit, the IR and IZ drop produced by surge current
raises the chassis of the protected equipment to a very high potential. If
that product is connected to ANYTHING that is grounded elsewhere (an
antenna, or equipment plugged into a different outlet) the difference in
potential is quite likely to fry both pieces of equipment. This used to be
a major problem in the pro audio world until we found series mode surge
suppressors, and it's still a problem in the computer world. I've seen
several well-documented reports of lightning taking out everything connected
by Ethernet in homes and offices with no ham radio involved.
MOVs also have a limited lifetime -- after they have absorbed a certain
number of joules, they no longer do anything -- and they often fail
destructively. In cheaply constructed products, they could even start a
fire. The Isobars do not fall into that category, but a lot of power strips
with MOVs do.
MOV's are a fine solution at the power service entrance if they are properly
installed and the premises follows proper grounding and bonding, but on
branch circuits, they're likely to CAUSE as many problems as they might
prevent.
I know of two companies making series-mode protectors, both of which license
the same technology. Brick Wall sells in the consumer world, SurgeX to the
pro audio and video world. About 15 years ago, I started specifying their
products to protect racks full of very expensive small-signal equipment in
the large and small sound systems I was designing and specifying. As a
consultant, I had no part of the sale of equipment, nor did I get a
commission on anything -- rather, I was paid by the owner of the building
for whom I was designing the system, or by his architect.
About ten years ago, because I was well known as a technical writer, SurgeX
asked me to write a tutorial for them on power and grounding for audio and
video systems, and since about 2004, I've been teaching classes on that
topic at industry trade shows. As a result, I know more about their
products than about Brick Wall.
73, Jim K9YC
------------------------------
Message: 2
Date: Sun, 16 Sep 2012 13:57:32 -0700
From: Jim Brown <jim@audiosystemsgroup.com>
To: Rfi List <rfi@contesting.com>
Subject: Re: [RFI] ISOBAR
Message-ID: <50563D3C.5030605@audiosystemsgroup.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 9/16/2012 1:24 PM, Ed Douglass wrote:
> Would I be correct in thinking that an MOV device at the end of a branch
circuit would NOT be bad news so long as all the computer and peripheral
equipment Is plugged into the MOV device?
There would not be the potential difference problem, but the inherent
problems of MOVs (lifetime, blowing up (they DO blow up if you hit them with
surges at the 6kV that IEEE studies show can exist on interior wiring).
> I other words none of the computer equipment has a ground connection away
from the surge protector.
>
> Can you think of a likely way in which we could fooled? E. g. A drain
wire in a shielded CAT-5 cable.
Although Ethernet line drivers and receivers may be isolated by a
transformer, the high potential of a lightning event can (and will) arc
across it and take out the equipment. I know of several instances of that
happening, the guys suffering the events were engineers, and the
CAT5 cable was NOT shielded.
73, Jim K9YC
------------------------------
Message: 3
Date: Mon, 17 Sep 2012 06:20:45 -0400
From: Pete Smith N4ZR <n4zr@contesting.com>
To: rfi@contesting.com
Subject: Re: [RFI] ISOBAR
Message-ID: <5056F97D.7000307@contesting.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Our whole-house protector (from the power company) comes with good insurance
for things inside the house provided that you cascade a point-of-use surge
protector. They seem to assume that the latter will be MOV-based. Is this
a way to get around the IR/IZ drop problem so that one doesn't have to spend
$200-500 for even consumer-grade Brick Wall products?
73, Pete N4ZR
The World Contest Station Database, at www.conteststations.com The Reverse
Beacon Network at http://reversebeacon.net, blog at
reversebeacon.blogspot.com, spots at telnet.reversebeacon.net, port 7000 and
arcluster.reversebeacon.net, port 7000
On 9/16/2012 1:12 PM, Jim Brown wrote:
> On 9/16/2012 2:22 AM, Christopher Brown wrote:
>>
>> On 9/15/12 5:46 PM, Jim Brown wrote:
>>> I can't comment about RF filtering, but it's an MOV box, which is
>>> BAD NEWS on a branch circuit.
>> Care to explain or provide a ref?
>
> The fundamental problem is that MOVs, like all shunt protectors,
> attempt to short out the surge, mostly by conducting it to ground.
> When the MOV is at the end of a branch circuit, the IR and IZ drop
> produced by surge current raises the chassis of the protected
> equipment to a very high potential. If that product is connected to
> ANYTHING that is grounded elsewhere (an antenna, or equipment plugged
> into a different outlet) the difference in potential is quite likely
> to fry both pieces of equipment. This used to be a major problem in
> the pro audio world until we found series mode surge suppressors, and
> it's still a problem in the computer world. I've seen several
> well-documented reports of lightning taking out everything connected
> by Ethernet in homes and offices with no ham radio involved.
>
> MOVs also have a limited lifetime -- after they have absorbed a
> certain number of joules, they no longer do anything -- and they often
> fail destructively. In cheaply constructed products, they could even
> start a fire. The Isobars do not fall into that category, but a lot of
> power strips with MOVs do.
>
> MOV's are a fine solution at the power service entrance if they are
> properly installed and the premises follows proper grounding and
> bonding, but on branch circuits, they're likely to CAUSE as many
> problems as they might prevent.
>
> I know of two companies making series-mode protectors, both of which
> license the same technology. Brick Wall sells in the consumer world,
> SurgeX to the pro audio and video world. About 15 years ago, I started
> specifying their products to protect racks full of very expensive
> small-signal equipment in the large and small sound systems I was
> designing and specifying. As a consultant, I had no part of the sale
> of equipment, nor did I get a commission on anything -- rather, I was
> paid by the owner of the building for whom I was designing the system,
> or by his architect.
>
> About ten years ago, because I was well known as a technical writer,
> SurgeX asked me to write a tutorial for them on power and grounding
> for audio and video systems, and since about 2004, I've been teaching
> classes on that topic at industry trade shows. As a result, I know
> more about their products than about Brick Wall.
>
> 73, Jim K9YC
> _______________________________________________
> RFI mailing list
> RFI@contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
------------------------------
Message: 4
Date: Mon, 17 Sep 2012 06:22:04 -0400
From: Pete Smith N4ZR <n4zr@contesting.com>
To: rfi@contesting.com
Subject: Re: [RFI] ISOBAR
Message-ID: <5056F9CC.2010507@contesting.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
This happened to me repeatedly with nearby strikes, until I went to a
wireless network.
73, Pete N4ZR
The World Contest Station Database, at www.conteststations.com The Reverse
Beacon Network at http://reversebeacon.net, blog at
reversebeacon.blogspot.com, spots at telnet.reversebeacon.net, port 7000 and
arcluster.reversebeacon.net, port 7000
On 9/16/2012 4:57 PM, Jim Brown wrote:
> Although Ethernet line drivers and receivers may be isolated by a
> transformer, the high potential of a lightning event can (and will)
> arc across it and take out the equipment. I know of several instances
> of that happening, the guys suffering the events were engineers, and
> the CAT5 cable was NOT shielded.
------------------------------
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