Safety Ground Conditioning

0 Members and 1 Guest are viewing this topic. Read 14666 times.

Occam

Safety Ground Conditioning
« on: 11 Aug 2013, 05:44 pm »
A while back, an occasional poster, rdsu, asked about ground conditioning chokes -
Interesting! :)

On Felix Topic, the authors and testers found that the best chokes for amplifiers, at 115V, that doesn't constraint dynamics, are the JW Miller 17A ou 20A. For 230V the 9.3A was used with success, maybe because of more current available...

Even the JW Miller 9.3A has more Inductance and less DC Resistance than Coilcraft 5A.

I have a friend that use Coilcraft 10A for their Amplifier, and he likes the result...

Did you also test them?

For Earth, you can try Schurter DENO ...

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.


« Last Edit: 11 Aug 2013, 11:26 pm by Occam »

Folsom

Re: Safety Ground Conditioning
« Reply #1 on: 12 Aug 2013, 12:32 am »
Occam,

After learning about the DENO units I ordered a few. You know what? I like them. I plan to continue use of them. The key to this is to use star wiring that is fed by the DENO, into isolated ground sockets. The box can be grounded before the DENO, or not. Another method is to use a grounding plate that is isolated from the box (connected, not as wire), then the DENO, and then isolated star grounding. The best part is they are cheap, so the added price to a unit is negligible.

Take a look at where the DENO's frequency range is at. I think you'll have your mh explanation there. They are basically romex solid wire wound around a donut. I don't think there is a need for worry because the inductance just isn't anywhere near line. Unless there is a secret subliminal .3mhz frequency in the EU at high amperage, that I'm unaware of....

Bybee's work well on ground as well. I've done a DENO and a Bybee into star grounding. It's on the unit with 17x Bybee's. It is STELLAR, but incredibly expensive.

I realize the one I linked too does way less. It's still a fascinating unit that inducts by looping onto itself. I thought the guy might be interested in developing some other practical stuff (we could use), but no.
« Last Edit: 12 Aug 2013, 11:02 pm by Salis Audio »

rdsu

Re: Safety Ground Conditioning
« Reply #2 on: 12 Aug 2013, 01:17 pm »
Hi Occam,

I use it on my "Felix" and works very well without issues...

Thanks one more time for your help! ;)

Regards

rdsu

Re: Safety Ground Conditioning
« Reply #3 on: 12 Aug 2013, 01:23 pm »
You also have more options:

Folsom

Re: Safety Ground Conditioning
« Reply #4 on: 12 Aug 2013, 11:26 pm »
The potted unit appears to be the same as the DENO, just, you know, potted. It's also more than twice the price.

The biggest upgrade is the super low impedance grounding mixture you can put your grounding rod into. It's all the rage for recording studios I guess.

jneutron

  • Full Member
  • Posts: 557
Re: Safety Ground Conditioning
« Reply #5 on: 13 Aug 2013, 03:43 pm »
Placing any reactive device into the grounding path of an AC feed it not a very wise idea. The reactance of the device will limit the bolted fault current, which will alter the time to clear the breaker in the event of a fault.

Doing this can cause the short current to exceed the ampacity of the wires.

jn

Wayner

Re: Safety Ground Conditioning
« Reply #6 on: 13 Aug 2013, 04:45 pm »
I'm with jn. I don't understand why you need to condition a conductor that is not supposed to carry any current. This is a safety conductor used to bleed current away from a fault.

Wayner

Folsom

Re: Safety Ground Conditioning
« Reply #7 on: 13 Aug 2013, 07:38 pm »
I doubt the reactance of the DENO could be a problem. The range it works in, the type of wire, and the amount of resistance don't point towards a reactive quality during a ground fault. jn do you really think it'd even be noticeable? I doubt dozens of them in a row would make a difference.

Ground noise is very real. Again the special earth ground rod blocks that can be poured change the situation significantly, but not many of us have that option. For example balanced cables could dump noise with the right impedance situation, through the earth grounded enclosure one pin is connected too, but as is now there isn't a consistent factor for where the noise goes. One member on the forum dislikes Y caps in a system with balanced interconnects because the noise ends up on ground, and then affecting the equipment with balanced interconnects. Maybe it is even Occam, I forget.

jneutron

  • Full Member
  • Posts: 557
Re: Safety Ground Conditioning
« Reply #8 on: 13 Aug 2013, 08:33 pm »
I doubt the reactance of the DENO could be a problem. The range it works in, the type of wire, and the amount of resistance don't point towards a reactive quality during a ground fault. jn do you really think it'd even be noticeable? I doubt dozens of them in a row would make a difference.
A few points..

NEC  250.8(B) does NOT allow the grounding and bonding of electrical equipment where the connections depend solely on solder.

NEC 250.102(D) requires the bonding conductor always be #14awg or larger.

NEC Article 100 defines "Grounded, Solidly" as "connected to ground without inserting any resistor or impedance device."

The bonding of equipment MUST guarantee that during a fault, the exposed surfaces cannot exceed 50 volts.  Inductance placed in series with the grounding conductor does not guarantee that. 

"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.  Faults will no longer clear in two or less line cycles, and you float the chassis off ground potential.

Edit:  Actually, your statement is extremely dangerous..

An inductor of 22 millihenries will cause the shorted current to be 14.46 amperes in a 120 volt line, and will not clear the line, leaving a chassis at 120 volts indefinitely.

4 mllihenries will cause an 80 ampere fault current. 

If one examines the time/current curve for a typical magnetic breaker, 80 amps on a 15 ampere breaker is supposed to clear the breaker in the range between 4 and 15 seconds.  While 15 seconds may not seem long to some, to others it can be a lifetime.

It is NEVER a good idea to insert any component in series with the safety bonding conductor.  There is a good reason for that.

So, to answer your question.....
Quote
jn do you really think it'd even be noticeable?

Yes.  I suspect death can be noticeable.  Or even just brown underwear.

jn

Speedskater

  • Full Member
  • Posts: 2214
  • Kevin
Re: Safety Ground Conditioning
« Reply #9 on: 13 Aug 2013, 08:51 pm »
It seems strange that a company who's mission is:

SCHURTER is an internationally leading innovator and manufacturer of fuses, connectors, circuit breakers, input systems and EMC products as well as a PCB assembly service provider for the electronics industry.

Would have a product like a:

DEH EMV Inductor: High frequency ground wire choke,

Folsom

Re: Safety Ground Conditioning
« Reply #10 on: 13 Aug 2013, 11:20 pm »
You're talking about electrical bonding. Those codes mean nothing for those that are using these items in electronics. I'm certain Schurter didn't intend for their devices to be used in electrical bonding situations. Correct me if I'm wrong but I'm unaware of any audiophile that build their system into the conduit of their pool.

Nothing is rated near 80a in the case of electronics. The very socket in the wall is not. Many devices have fuses as well.

The resonant frequency of the DENO is .3mhz. I'd like to know how you figure 60hz is going to become thermal.

 

Speedskater

  • Full Member
  • Posts: 2214
  • Kevin
Re: Safety Ground Conditioning
« Reply #11 on: 14 Aug 2013, 12:11 am »
The safety of and the rules for DIY equipment is the same as for store bought equipment.  The situation is if there is a short circuit then the Safety Ground circuit must be as robust as the Hot  & Neutral.  If a Safety Ground connection fails in that fraction of a second, then the breaker doesn't trip and someone could get electrocuted.

'electrical bonding' means a robust and secure permanent connection.

Folsom

Re: Safety Ground Conditioning
« Reply #12 on: 14 Aug 2013, 01:32 am »
Speedskater I always appreciate your interest in reading about safety, but mis-categorizing safety isn't helpful. This board has for whatever reason begun to make a habit of this.

Electrical bonding.

NEC: National Electrical Code. It doesn't have squat to do with electronic components. That field is only sometimes governed by UL depending on individual counties.

DIY equipment is often much more robust and safer than store purchased items. I understand the breaker situation. No one here has actually brought up a conflicting argument from safety. Codes that don't apply and have a different purpose (and are generally met by those using these products), unexplained reasoning of induction in different frequency ranges, non-complaints about size of wire, demands for current loads far exceeding the rating of the romex feeding anything anyone would use one of these units in....


Speedskater

  • Full Member
  • Posts: 2214
  • Kevin
Re: Safety Ground Conditioning
« Reply #13 on: 14 Aug 2013, 02:03 am »
I gave a very informal explanation of bonding.  Yes the NEC definition is much stricter as in attached forever.

I never suggested that NEC code was the only organization that applies to safety.

If the store bought equipment has a real safety sticker then we know the a knowledgeable organization tested it.

Some of the posts in the 'power conditioning' forum make me wonder about their DIY equipment's safety.

jneutron

  • Full Member
  • Posts: 557
Re: Safety Ground Conditioning
« Reply #14 on: 14 Aug 2013, 02:03 pm »
It is very important you discontinue the diversionary strawman tactics, they only serve to obscure the issue.This sentence as a point:

Quote
Correct me if I'm wrong but I'm unaware of any audiophile that build their system into the conduit of their pool.

The discussion has NOTHING to do with conduits nor pools.  STOP.   LISTEN.   NOW.  IT IS VERY IMPORTANT YOU UNDERSTAND.

You're talking about electrical bonding. Those codes mean nothing for those that are using these items in electronics. I'm certain Schurter didn't intend for their devices to be used in electrical bonding situations.
I do not care what Schurter intended.  I care about safety.  The name of this thread is Safety Ground Conditioning .

A safety ground is a ground used for safety.  PERIOD.  The purpose of a safety ground is to clear the breaker in the event a fault within a piece of electronics could cause the chassis to become energized.  And, while doing so, keep the chassis potential at a non lethal level.

Placing inductance within that path alters the fault current which clears the breaker.  Sufficient inductance can prevent the breaker from clearing.
Nothing is rated near 80a in the case of electronics. The very socket in the wall is not. Many devices have fuses as well.
It is important you follow the argument.  Go back and re-read what I said.

I'd like to know how you figure 60hz is going to become thermal.
Again, follow the discussion, or learn it.  A circuit breaker has two modes of operation.  One is thermal, and the other is magnetic.
I apologize for being so hostile sounding.  This is a safety concern, and I do not take hostages when safety is involved.

jn

rdsu

Re: Safety Ground Conditioning
« Reply #15 on: 14 Aug 2013, 03:33 pm »
About earth, I based my power conditioner on these two examples:

IsoTek GII SIGMAS


Shunyata Hydra Triton


I used the Schurter DENO 16A version, but at least I should use the 25A that has less resistance...

rdsu


jneutron

  • Full Member
  • Posts: 557
Re: Safety Ground Conditioning
« Reply #17 on: 14 Aug 2013, 04:04 pm »
An Introduction to AC Ground-Fault Loop Impedance Testing ?

A very nice link, the writing is not overly technical but provides good information.

One point.  The tables they provided are for 120 volt systems.. Members here who have different voltages must recalculate accordingly.

Note that the impedance of a 10 mH inductor at 60 hz is 3.7 ohms.

Also very important:  Those tables use 500% fault current, and expect the breaker to clear in about 1 second.  If you look at the 15 ampere with 75 amps fault, and then look at the time/current chart of a circuit breaker, you may find that the actual time to clear is between 5 and 15 seconds by design. 

For that table and typical breakers, the chassis will be energized at FULL LINE VOLTAGE for a time between 5 and 15 seconds.

Note:  This assumes a hot to chassis short of course.  It is the worst case, and the reason for a safety ground.

Another note:  If you have two devices, like a pre and amp, and one shorts to ground, you are now using the shield of the IC to try and hold chassis potential down. 

jn

Speedskater

  • Full Member
  • Posts: 2214
  • Kevin
Re: Safety Ground Conditioning
« Reply #18 on: 14 Aug 2013, 04:42 pm »
Thoughts:

a] An additional 3.7 Ohms will definitely slow down a breakers trip time by a lot.  If the total series impedance is 8 Ohms, a 15A breaker will never trip.

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.

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.

DaveC113

  • Industry Contributor
  • Posts: 3981
  • ZenWaveAudio.com
Re: Safety Ground Conditioning
« Reply #19 on: 14 Aug 2013, 04:45 pm »

Another note:  If you have two devices, like a pre and amp, and one shorts to ground, you are now using the shield of the IC to try and hold chassis potential down. 

jn

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.