Safety Ground Conditioning

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jneutron

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Re: Safety Ground Conditioning
« Reply #21 on: 14 Aug 2013, 05:25 pm »
b] If a 15A circuit is used to power a bunch of old fashioned filament light bulbs. If the continuous current is 12A (all that's permitted in a 15A circuit) then the cold turn-on current could approach 120A in the first second.
I suspect the incandescent bulb transient is in the tens to maybe 100 millisecond range, but do not recall any data on that.
c] While the safety margin continuous current limit for common 14AWG wire is 15A the real limit is 27 to 29A.  But under fault conditions that 14AWG wire will fail after 1 second at 600 Amps.
600 amps is 40 times rating, that falls into the magnetic operation of a 15 amp breaker.  It clears in 1 line cycle, or 16.6 milliseconds.


http://static.schneider-electric.us/docs/Circuit%20Protection/Molded%20Case%20Circuit%20Breakers/0100-400%20A%20Frame%20FA-LA/FA-FC-FH/0600DB0105.pdf
Page 2 has a typical curve for square D.

jn

jneutron

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Re: Safety Ground Conditioning
« Reply #22 on: 14 Aug 2013, 05:36 pm »
Good thread!

Assuming both components are grounded then the ground wires in the power cords and building wiring also connect the grounds along with the IC's ground wiring.

If you assume that a "box" is used and all components are plugged into is like the second picture, then indeed all the chassis will go to the same potential.  So while dangerous voltages may appear on the chassis, it will appear on all of them.

If one component has it's ground via a different inductor, there will be an inter-chassis potential difference, and the IC shield will be hit very hard.  If it opens, the electronics at both end of the IC are also toast.

jn

jneutron

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Re: Safety Ground Conditioning
« Reply #23 on: 14 Aug 2013, 05:40 pm »
Earth-fault loop impedance values, for 240V.
MAXIMUM EARTH FAULT LOOP IMPEDANCE VALUES FOR OVERCURRENT PROTECTIVE DEVICES IN COMMON USE, FOR FAULT PROTECTION

Should I remove the earth choke?
Do you have children?

I believe following code is the best option.  Oh, btw..  are the devices UL?

I am reminded of the old dirty harry scene...  In all the confusion, I don't recall if I fired 5 times, or 6..are you feeling lucky...

jn

Folsom

Re: Safety Ground Conditioning
« Reply #24 on: 14 Aug 2013, 06:38 pm »
jn, safety is within understanding. It's respect, not fearful avoidance. Respect produces predictability, fear produces a defense position that is regardless of predictability.

I'm not sure why you are comparing a 10mh inductor now.

If only earth ground was nearly as effective as we would like.

The resistance of the DENO's are rated in milliohm
« Last Edit: 15 Aug 2013, 01:06 am by Salis Audio »

Speedskater

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Re: Safety Ground Conditioning
« Reply #25 on: 14 Aug 2013, 07:00 pm »
That earth ground in the dirt only matters in thunderstorms and the like.  Inside a building the Safety Ground's job is to trip it's circuit breaker if there is a fault (short circuit). The less series resistance/impedance of the Safety Ground wiring back to it's circuit breaker box, the better.

jneutron

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Re: Safety Ground Conditioning
« Reply #26 on: 14 Aug 2013, 07:40 pm »
jp, safety is within understanding. It's respect, not fearful avoidance. Respect produces predictability, fear produces a defense position that is regardless of predictability.

I assume you meant jn..

I am not avoiding anything because of fear.  I am pointing out the very serious safety errors you have presented.  Insertion of a device with impedance into a safety conductor is dangerous.

I teach advanced electrical safety outside the scope of what we would call normalcy...your misconceptions are going to end up as part of my course material.  In fact, I believe the standard safety course given as a precursor to mine already has some of this stuff in it.

I'm not sure why you are comparing a 10mh inductor now.
I am not comparing anything.  I pointed out what the inductive reactance of a 10 millihenry coil was at 60 hz to show the level of effect.

If only earth ground was nearly as effective as we would like.

MIke Holt is a great site and resource.  Unfortunately, you are linking about earthing?  We are discussing safety bonding of equipment chassis, not earthing for lightning strike protection.

The more you post, the clearer your lack of understanding on grounding and earthing becomes.  As I said, please learn this stuff.  What you present is dangerous.

The resistance of the DENO's are rated in millionths of an ohm.

Where are you getting this???  A #12awg wire has DC resistance of 1.7 milliohms per foot.  One inch is 141 millionths of an ohm.

The term m ohm means milliohms, not micro-ohms. 

jn

rdsu

Re: Safety Ground Conditioning
« Reply #27 on: 14 Aug 2013, 08:29 pm »
Do you have children?
Yes, 14 months old... ;) That is why I really need to know...

Where are you getting this??? 
From here: Schurter DENO

jneutron

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Re: Safety Ground Conditioning
« Reply #28 on: 14 Aug 2013, 08:41 pm »
Yes, 14 months old... ;) That is why I really need to know...
From here: Schurter DENO

Ah, my apologies. It was a rhetorical question.  I had examined the link before, so knew of the 2 to 4 mH inductance.

Quite honestly, the possibility of your system having a hot to chassis fault is very low.  The real question is..  is the risk, no matter how low in probability, worth it?

When loved ones are involved, is any avoidable risk worth taking?  To me, I weigh risk probabilities based on the cost of the worst possible outcome.  With children, that cost is infinite.

jn

Elizabeth

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Re: Safety Ground Conditioning
« Reply #29 on: 14 Aug 2013, 09:18 pm »
As a child I stuck my fingers with tools of some sort into PLENTY of AC outlets.
I am still, sad to say, alive.
(I did see my 280lb dad get tossed five feet across a room while trying to fiddle in the back of our tubed, not solid state color TV while it was turned on, back in the 1960's, which I would guess was he touched the high voltage something..)
In 64 years I have never had an electrical component fail to a live chassis. Nor have I read nor heard of ANY child anywhere getting electrocuted by a stereo component which was improperly grounded.
So I have to say the worry about our precious children may be a little over the top?
Just my opinion there.

Occam

Re: Safety Ground Conditioning
« Reply #30 on: 14 Aug 2013, 10:08 pm »
.....
I think these Schurter doohickeys are ideal for their task, providing substantial inductance in a very small, purpose built package. I'm surprised no one has commented positively.

on the second page... and no one finds it interesting odd that this ground choke is a differential 2 terminal inductor, one inch in diameter, weighing 1 ounce



and yet, it is rated 16 amps and 4 milli Henrys?????????
Well,  actually, not at the same time.... 8)

EDIT:changed differential inductor to 2 terminal inductor
« Last Edit: 15 Aug 2013, 02:27 pm by Occam »

Folsom

Re: Safety Ground Conditioning
« Reply #31 on: 15 Aug 2013, 01:17 am »
Sorry, yes, jn. And Millionth is the spell-check word that comes up for milliohm; a habitual mistake.

Actually according to what you said, a 4mh device is perfectly fine but...

Occam's the one pointing out the rating concerns. The resonate frequency, again, is .3mhz. "Not at the same time," as he says for current, induction (and there for series reactance properties).

The reality is that it isn't a very strong filter.

Occam

Re: Safety Ground Conditioning
« Reply #32 on: 15 Aug 2013, 02:11 am »
.....
Occam's the one pointing out the rating concerns. The resonate frequency, again, is .3mhz. "Not at the same time," as he says for current, induction (and there for series reactance properties).
.....

Nope.

Folsom

Re: Safety Ground Conditioning
« Reply #33 on: 15 Aug 2013, 02:18 am »
?

jneutron

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Re: Safety Ground Conditioning
« Reply #34 on: 15 Aug 2013, 12:54 pm »
As a child I stuck my fingers with tools of some sort into PLENTY of AC outlets.
I am still, sad to say, alive. (there is only so far the regulating agencies can go to counter the stupidity of the average individual.  I can also say that it does indeed hurt, me it was a pair of small scissors.)(I did see my 280lb dad get tossed five feet across a room while trying to fiddle in the back of our tubed, not solid state color TV while it was turned on, back in the 1960's, which I would guess was he touched the high voltage something..) (good guess.  Early color TV's had inefficient phosphors, 17kv was pretty much the level.)
In 64 years I have never had an electrical component fail to a live chassis. Nor have I read nor heard of ANY child anywhere getting electrocuted by a stereo component which was improperly grounded. (Nor I.  Look up the stats on electrocutions in the US alone.  Granted, a few hundred dead out of 300 million is very small.)

So I have to say the worry about our precious children may be a little over the top? (or significant other, or sibling, or burning the house down..name your poison.)
Just my opinion there.(no prob)

But your position seems to be to ignore safety problems because you haven't experienced it?  Do you believe that is a reasonable stance to present on a DIY forum?

jn

jneutron

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Re: Safety Ground Conditioning
« Reply #35 on: 15 Aug 2013, 02:16 pm »
on the second page... and no one finds it interesting odd that this ground choke is a differential inductor, one inch in diameter, weighing 1 ounce



and yet, it is rated 16 amps and 4 milli Henrys?????????
Well,  actually, not at the same time.... 8)
I'm not sure what is interesting or odd.  The datasheet I see doesn't say differential inductor, so I'm also not sure what is meant by that.
16 amps seems ok, as does 4 millihenries..  Why not at the same time?  Are they indicating that it saturates, dropping inductance as a consequence?  I didn't see a current vs inductance graph.

jn

jneutron

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Re: Safety Ground Conditioning
« Reply #36 on: 15 Aug 2013, 02:36 pm »
Sorry, yes, jn. And Millionth is the spell-check word that comes up for milliohm; a habitual mistake.

I too used to be able to spell, and then spellchecker arrived..sigh.

Actually according to what you said, a 4mh device is perfectly fine but...
Don't let the numbers confuse.  Think about the system during a fault.

a 4 mH inductor will have a reactance of 1.48 ohms.  At fault, that will draw 81 amperes.

In a 15 ampere branch circuit, that represents a factor of 5.4 over the nominal.  The breaker will break in the timeframe of 3 to 12 seconds.  Until that interval has passed, the chassis will be at 120 volts.

In a 20 ampere branch circuit, the factor is now 4.  The 20 amp breaker will clear between 6 and 20 seconds.  Again, the chassis will be at 120 volt potential during that interval.

In a 30, the factor is 2.66, 15 seconds to 60 seconds with a chassis at 120 volts..

Note that for all breakers, they are designed NOT to open faster than the low time point shown on the breaker time/current curve.

My point here is:  This discussion is all about a SAFETY FEATURE used to protect us.  Insertion of an inductance into the bonding conductor must NEVER be done without engineering analysis to determine the level of effect the compromising of a safety feature will have on the overall system.

You in fact, did not understand the use of the term "thermal" with respect to a circuit breaker.. Consequently, you had no idea that the use of these devices in the safety conductor would cause a chassis to be AT LINE VOLTAGE for a time period designed in by the circuit breaker manufacturer.

You can no longer claim that lack of knowledge..

To all:  a circuit breaker is there for only ONE reason.  That reason does not include the protection of human lives directly.  It's sole purpose is to protect the wires from the breaker to the load.  Nothing more, nothing less.

It is our responsibility to make sure that during a fault, humans are protected.  That is why insertion of an inductance in the safety grounding conductor without proper engineering  is so dangerous, it compromises safety.

jn

Folsom

Re: Safety Ground Conditioning
« Reply #37 on: 15 Aug 2013, 05:22 pm »
jn, I thought you were saying the induction device would become thermal? I don't think "thermal" is an overly complicated function.

I'm contacting the company because several factors will influence our concerns here about safety. There are simply questions not answered.

jn, might I suggest that you do your best to explain with information, and not a projection of how you feel people need to be safe. For example Elizabeth's values on safety vs. sound quality vs. risk vs. family, etc may be different than yours. If we wanted to be really safe we'd just not use electricity... Yet for whatever reason we have been using since the dark days when almost all electrical stuff was much more dangerous than anything discussed in this thread. I mean AC receptacle sockets way back would fail by shooting a fireball out of them... Anyway, give people all the information they can possibly use and then accept that they can do whatever they want, wrong or right, because they are sentient. Become concerned when they are wiring public buildings and make them stand up to code.

I have a fuse in my apartment (old), and there isn't any ground wires. I've grounded my listening system's socket to the conduit for some added protection. But as you may imagine I don't live with the safety that you'd promote. Yet the building and occupants have been around longer than either of us (and probably our ages combined).

jneutron

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Re: Safety Ground Conditioning
« Reply #38 on: 15 Aug 2013, 06:35 pm »
jn, I thought you were saying the induction device would become thermal? I don't think "thermal" is an overly complicated function.

No.  The statement I made (quoted after this sentence) was based on your statement:
Quote
"Dozens of them in a row" virtually guarantees that you have moved the fault current from the magnetic regime of the load panel circuit breakers into the thermal regime.
Your statement appears to be only considering the DC resistance of the elements.  If it were only a dc circuit, you would be correct.  It is the inductance which is the problem.

Most of the panel mount circuit breakers have an area of operation where a thermal heating device opens the breaker in a clearly defined time fashion, and a second regime where a magnetic element opens it up.  Many who do not know circuit breakers do not know of this fact.
I'm contacting the company because several factors will influence our concerns here about safety. There are simply questions not answered.
Always a good thing.  But just be wary as they are in the market to sell product.
jn, might I suggest that you do your best to explain with information, and not a projection of how you feel people need to be safe. For example Elizabeth's values on safety vs. sound quality vs. risk vs. family, etc may be different than yours.
Everybody weighs things differently.  I pointed out MY weighing scheme.  It actually does not matter to me how others weigh risks.

What DOES matter to me is that when someone makes a decision to alter or ruin a safety device, that they know exactly the ramifications of their actions.  For this specific item, it's use  will totally destroy the safety conductors ability to keep the equipment external surfaces from rising to lethal levels, and without any engineering involved, some combination could actually eliminate the system's ability to force the breaker to clear the line, leaving lethal potentials on external surfaces unchecked.

Given that the home environment is in essence an uncontrolled one, this action has the ability to subject others to lethal potentials in the event of a fault.  Others who are unknowing.

I didn't say people cannot make decisions based on their own weighing scheme.  I say, understand the ramifications of the decision.

If somebody is injured or dies as a consequence of ignoring my safety concerns, it cannot be said that it was not understood.

Sigh..you really need to break away from this hyperbole/strawman schtick you keep trying to use...it serves no useful purpose.
If we wanted to be really safe we'd just not use electricity... Yet for whatever reason we have been using since the dark days when almost all electrical stuff was much more dangerous than anything discussed in this thread. I mean AC receptacle sockets way back would fail by shooting a fireball out of them... Anyway, give people all the information they can possibly use and then accept that they can do whatever they want, wrong or right, because they are sentient. Become concerned when they are wiring public buildings and make them stand up to code.

The reason Code it there is to protect us.  It is updated every three years to fix errors, omissions, newer understandings, newer technology.  Your argument is tantamount to "hey, it's a dangerous world, so lets ignore the safety features others are attempting to impose on us.

But as you may imagine I don't live with the safety that you'd promote.

Don't be silly, of course you do.  You just are unaware of a lot of the technology.  Your building wire guage was defined by code.  Your fuses were defined by code, the outlets..

How many pieces of electrical equipment do you own with a 3 prong cord, where the manufacturer disabled the safety ground conductor?  How many do you think exist out there?

I can confidently say, none.  And I guarantee that none of them condone the practice of adding a component to their equipment to bypass the safety function either.

I've never been in a car accident, but I use seat belts and have not disabled the air bags.

If someone on an internet forum made the argument that they've never been in a car accident so seatbelts are unimportant, would you jump off that cliff as well?


Please be more cognizant of the arguments you present on a public forum.  The casual and uninformed disabling of safety items for use in a consumer home environment can have serious consequences.

And if you're going to provide anecdotal examples, make sure they are applicable, relevant, and viable.

jn

Elizabeth

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Re: Safety Ground Conditioning
« Reply #39 on: 15 Aug 2013, 07:04 pm »
But your position seems to be to ignore safety problems because you haven't experienced it?  Do you believe that is a reasonable stance to present on a DIY forum?

jn

Yes. When the 'safety' is so extreme it is over the top.
Just like worrying that using an aftermarket powercord will invaidate your home insurance in case of fire because none of the aftermarket cords are UL rated. (which is a claim bandied about by other 'too safe' worrywarts..)
Not one instance of an audiophile getting denied insurance has ever been  mentions on the internet with it being due to the cord not being UL approved. So it DOES get to be  a BS overkill too many times.
And I am just pointing that out for the folks who like to spout this sort of stuff.

Now yes it is true mentioning it is good.. As: It would be somewhat unsafe per these reasons: blah blah.. would be nice for all to understand. But to couch the message in terms with dire consequences.. Like "Your children will all die" sucks.
You do NOT have to make it overkill. a nice comment is all you need.

Aded: and your comments after the quoted post i wrote about are a little better. I read the responses and they do not exhibit that overthe top stuff. Rather a more reasoned comment.
So maybe it was just the 'Save the children' which got me annoyed.