Re: How to PostMortem?
From: w_tom (w_tom1_at_hotmail.com)
Date: 04/22/04
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Date: Thu, 22 Apr 2004 12:12:13 -0400
The warranty is so chock full of "qualifications and
conditions" as to be useless - except maybe to get the APC
product repaired or replaced. Specification numbers were not
available because the manufacturer does not even claim to
provide that all so essential common mode transient
protection. Common mode transients are THE destructive
transient.
But even worse, manufacturer instead claims filtering.
Miles of non-conductive air did not stop the transient. Will
a few inches of filters inside that APC stop what miles of air
could not? Of course not. Having read those citations from
www.tvtower.com and from www.polyphaser.com , obviously
protection is about earthing - and where that earthing is
performed. No effective protector claims to stop, block,
filter, or absorb the transient. Its just not possible.
Effective protector shunts (diverts, connects, terminates)
destructive transient to earth at building entrance. In
short, that UPS only claim, for all effective purposes,
blackout and brownout protection.
For residential transient protection, effective devices are
installed at the service entrance. One minimally effective
protector is even sold in Home Depot as Intermatic EG240RC or
IG1240RC. Minimally necessary for residential protection.
That would be maybe one dollar per protected appliance. Other
units are from Leviton, Square D, and many other lesser known
manufacturers.
Your breaker box better not (and probably does not) use 12
AWG to connect to earth ground and water pipe. Earthing wire
and wire to remove electricity from water pipe must be 6 AWG
or heavier.
Lets assume the 15 foot from computer room to breaker box
will attempt to earth a trivial 100 amp transient. Due to 12
AWG green wire impedance (not resistance), that wire might be
40 ohms. 100 amps on that 15 foot wire would leave computer
at maybe 4000 volts relative to the breaker box. Will
transient use that green safety ground wire to obtain earth
ground? Not completely due to wire impedance and as
demonstrated by that 4000 volts. One most typical and
destructive connection to earth ground is via motherboard and
modem, down phone line. Notice why modem is so easily
damaged. Modem makes a destructive path to earth ground.
Again, effective transient protection is at the service
entrance where everything - including the telco installed
protector - connects to that eight foot ground rod.
Effectiveness of any protector is defined by connection to and
integrity of that eight foot ground rod. Some location
install far more than one rod because better protection is
required. IOW surge protector is defined by its earth ground.
Incoming CATV also connects to that single point ground by
direct hardwire connection - no protector necessary. Again,
earth ground (not protector) defines transient protection.
Cable needs no protectors but still required that single point
ground. These connections typically are 12 AWG or larger and
should also be less than 10 foot with no sharp bends, no
splices, not through metallic conduit, etc.
Any protection that will work at the computer is already
inside the computer. Irrelevant whether your UPS outputs a
sine wave since the point was computers are so resilient as to
not be damaged even by spiky battery backup UPSes. So
resilient that household generated noise is irrelevant.
However, internal computer protection may be overwhelmed if a
massive incoming common mode transient is not earthed at the
service entrance by secondary protection - the 'whole house'
protector and eight foot ground rod. Demonstrated by this
manufacturer's example:
http://www.erico.com/public/library/fep/technotes/tncr002.pdf
Also computer's internal protection assumes your electric
company has maintained their earth grounds - your primary
protection - as demonstrated by www.tvtower.com .
The apcc white paper makes a few assumptions. For example,
how does a transient find earth ground via modem? It
completely bypasses power supply. The point "C" (power supply
passes power line transient to the computer circuits) in that
white paper assumes transient will pass through power supply.
Why. Power supply provides thousands of volts of isolation.
But green safety ground wire connects directly to IC on modem
- via chassis and motherboard. Green safety ground wire is a
direct connection they bypasses power supply.
The white paper does not even properly define a common mode
transient. Picture must include cloud, house, and earth
beneath. The electric circuit is from cloud, to wire entering
house, through computer inside that house, to earth ground,
and then to charges located on earth maybe miles away. That
is a common mode transient. Protection is to change the
circuit path so that common mode transient does not even go
inside house. It finds earth ground both on telephone pole
wires and where wire enters home. The white paper takes a
myopic perspective. Limit description of a common mode
transient only to wires at the computer which is why the truly
destructive transient is not fully appreciated by that white
paper.
The whole concept about protection is the single point
ground. Perspective must be larger to include cloud and
earth. Unfortunately
we still don't build as if the transistor exists. If we did,
a superior earth ground would be standard. Ufer grounding
makes superior single point and equipotential earthing.
Earthing - and not protectors - define the protection.
Protection must be a building wide solution which a plug-in
UPS simply avoids discussing in both specifications and white
paper.
Jean-David Beyer wrote:
> w_tom wrote (in part):
>> If your three UPSes have serious surge protectors, then you
>> can provide the numerical specifications that describe how
>> well they perform for each type of surge. I keep asking for
>> and no one has ever been able to provide specs to prove this
>> protection. Furthermore how does that UPS earth the typically
>> destructive transient when it is, virtually, not connected to
>> earth.
>
> I cannot give you the numbers you request, but the manufacturer
> implies that their effectiveness is high with the following words:
>
> "Surge energy rating 880 joules
> Filtering Full time multi-pole noise filtering: 0.3% IEEE
> let-through: zero clamping time: meets UL 1449"
>
> "American Power Conversion's Equipment Protection Policy:
> ...
> For customers that meet the qualifications and conditions set
> forth in this policy, APC will provide reimbursements (cost of
> repair or fair market value) during the period limits and up to
> the dollar limits stated as follows:
>
> [for the units I have]
> Dollar Limit $25,000
> Period Lifetime"
>>
>> You are confusing safety ground with earthing. To be
>> effective, the UPS must make a less than 10 foot connection
>> to EARTH ground.
>
> Of course, that is impossible in a residential situation. The best
> that can be managed is using the green wire both as a safety
> ground and an earthing connection. The electrical code around here
> requires that the power panel be connected to earth as close as
> possible using two separate connections. In my case, one uses a
> #12 guage wire less than 5 feet long going to a stake at least 8
> feet long into the ground. The other, also #12 guage wire, is
> probably 10 to 15 feet long and goes to the cold water supply
> pipe just as it enters the house.
>
> The panel contains two circuit breakers that supply the two
> computer power sockets. Nothing else is connected to those
> circuit breakers. 3-wire #12 guage cable goes from the breakers
> to the outlets. Each of those cables is probably 10 to 15 feet
> long.
>
> I am not as concerned with common mode noise as you seem to be, it
> would be generated mainly in the connection to earth from the
> power panel to the ground stake less than 5 electrical feet away.
> Any voltage generated in that 5 foot wire would affect both
> outlets the same, so while the computers might be going up and
> down in potential due to common mode noise in the 5-foot wire, the
> difference between them would be negligeable.
>
>> That means UPS must be part of or at breaker box. Building
>> wide UPSes are effective because a short earth ground is part
>> of the installation.
>
> Out of the question in a residential situation.
>
>> But plug-in UPSes are not located and connected less than 10
>> foot from earth ground. Earth ground - not safety ground - is
>> essential for effective protection. That fault light reported
>> a safety problem - and could never report the existence of
>> earth ground. No earth ground means no effective protection.
>>
>> Your description of a green wire connection back to breaker
>> box is an earthing path? But if that green wire does carry
>> the destructive 'direct strike' surge, then green wire only
>> induces that transient on all other adjacent wires.
>
> The transient induced by the common-mode connection, right? And
> that is the wire from the power panel through a wire less than
> 5 feet long from the power panel to the earthing ground stake.
>
>> Now we have additional induced transients throughout the building
>> as well as the direct strike. Not only must the connection from
>> each utility wire to earth ground be less than 10 feet. It
>> must also have no sharp bends, no splices, and not be bundled
>> with other non-earthing wires. Destructive transient must be
>> dumped into earth before that transient can enter a building.
>> Well proven concept from before WWII. Green wire ground
>> violates all three criteria for effective protection.
>>
>> This problem with a green wire safety ground is why your UPS
>> manufacture avoids the entire discussion.
>
> My manufacturer does discuss this:
> http://www.apcc.com/tools/mytools/index.cfm?action=search&category=whitepaper
>
>> Notice that discussion about earthing never comes from the
>> manufacture of ineffective protectors. But real world
>> (serious) manufacturers discuss earthing extensively:
>> http://www.polyphaser.com/ppc_technical.asp
>> http://www.polyphaser.com/ppc_pen_home.asp
>>
>> Running a dedicated circuit to computers is nice. But it
>> does not do anything worthwhile for noise or transient
>> protection - from a computer's perspective. Nothing in the
>> house creates noise or transients that adversely effect a
>> computer. Computer power supplies are some of the most
>> resilient devices in the house. So resilient that this UPS
>> creates 120 VAC in battery backup mode by outputting two 200
>> volt square waves with a 280 volt spike between those 200 volt
>> waves.
>
> My UPSs produce sine wave output.
>
> Since the computer power supplies are switching type (the big
> one with power factor control), they can probably tolerate
> pretty bad input waveforms.
>
>> An example of protection cited by an APC product:
>> SURGE PROTECTION AND FILTERING
>> ...
>> Normal mode clamping response time 0 ns, instantaneous
>> Normal mode surge voltage let through <5% of test peak voltage
>> when subjected to IEEE 587 Cat. A 6kVA test
>> Normal mode noise suppression Full time EMI/RFI
>> filtering
>> Modem/10Base-T/100Base-Tx network cable port single line
>> (2 wire, RJ11) or network (UTP, RJ45) compatible jacks
>>
>> Where is the common mode protection? It is not even
>> claimed. ...
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