John Curl's Blowtorch preamplifier part II - Page 2285 - diyAudio
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Old 1st May 2012, 02:46 PM   #22841
zinsula is offline zinsula  Switzerland
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Quote:
Originally Posted by jneutron View Post
[...]Are you suggesting that whenever a diode bridge is used to break a ground loop, there must also be a GFI feeding the system so that the diode bridge (which is unacceptable from the NEC regulations because it's so wimpy) is protected? [...]
I wonder what's wrong with that.
Such parts are cheap, and this is DIYAudio.

Apart that your min. 4mA and max. 6mA requirements are awkward here in Europe.
Switzerland has 30mA, doesn't matter if its a mobile connector or a house installation, and you may have those which are arbitrarily delayed, i.e. they do not trip after two periods.

You could also use a Thermistor instead of a bridge. Pass Labs do that, AFAIK.
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Old 1st May 2012, 02:47 PM   #22842
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Originally Posted by vacuphile View Post
typically
Me atypical (again).

1st (ground) floor bathroom, completely redone by a pro contractor ~5 years ago.
Earth net under the floor tiles, everything grounded, including the automated rinse & blow-dry toilet seater.
(2nd and 3d floor bathrooms are fully grounded too, combined electrical floor heating and earth net, with a connection to a GFCI, did those two myself)
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Old 1st May 2012, 02:48 PM   #22843
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John (N)

The neutral and ground are supposed to be bonded at building entrance, as you know.

Now a typical domestic electric panel will have a neutral bar and an optional ground bar. If you look at a typical box the added ground bar is screwed to the metal box without insulation at the building entrance panel. The neutral is brought in to the neutral bar as it usually has a slot or two big enough for the neutral. Now if the installer ties the three (current code) ground rods (or pipe attachment) to the same neutral bar there is only conduction from the safety ground to the physical ground through the screws holding in neutral and ground bars through the case.

Another case would be if the grounding connection was only attached to the safety ground bar. In that case the current surge on the neutral could easily be large enough and fast enough that little is diverted to the grounding system. It gets worse on the older single ground systems.

Now take the worst case, a single ground to the isolated ground buss bar. A 12 gauge jumper to the neutral buss where the neutral is connected. That would have met code in the past. Then when lighting hits the neutral everything in the house frys!


As to the 6 volts permitted between neutral and safety ground. If more than even a few hundred millivolts is present the "safety" diodes begin to conduct! At 1.4 volts they will be close to their limit. As there is a limit on the 6 volts but not the current to produce the voltage, your diodes can fail even on an outlet that meets code.

ES

Last edited by simon7000; 1st May 2012 at 02:51 PM.
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Old 1st May 2012, 02:56 PM   #22844
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Originally Posted by john curl View Post
That's what I normally do, Hitsware. '-)
Good for you. That's one thing about high end,
as opposed to mass marketing, one has a little
more slack with the ' rules '.
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Old 1st May 2012, 03:14 PM   #22845
Bonsai is offline Bonsai  Taiwan
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On both sets of recordings, there's no compression, limiting, or EQ. They both make my puppy howl. Ceiling is lower than I'd like, about 3 meters. Concrete floor covered with thick padding and carpet.

SY, can you share your music with a link?
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Old 1st May 2012, 03:19 PM   #22846
SY is offline SY  United States
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SY, can you share your music with a link?
Stuart Yaniger's sounds on SoundCloud - Create, record and share your sounds for free

Side note: "The Last Remaining Beatle" is a reworked version. In the original song, the first verse went:

"The last remaining Beatle will slaughter Michael Jackson
He'll strangle him to death while he's sleeping.
He'll strike with such a surgical precision, he won't even wake the preteen boys in the bed.
He'll take his clip on nose for a souvenir
and say, "The King of Pop is done here!"

Since the release of the album "Cruelty," Jackson died, so Southpaw (being a MUCH nicer person than I) rewrote that part to make it kinder.
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Old 1st May 2012, 03:36 PM   #22847
wayne is offline wayne  United States
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Jacco who makes the toilet seat? I need to check my wiring is GFI back home where I tapped in!
I think of the testing and safety we do on amplifiers and then look at the toaster here in Italy with no timer and wire baskets to hold the bread?
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Old 1st May 2012, 03:40 PM   #22848
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Quote:
Originally Posted by zinsula View Post
I wonder what's wrong with that.
Not a thing.. I though I made it very clear that I thought the idea great..
Quote:
Originally Posted by zinsula View Post
Apart that your min. 4mA and max. 6mA requirements are awkward here in Europe.
Hey, I'm the messenger here.. It's not my numbers, its per code here.
Quote:
Originally Posted by zinsula View Post
Switzerland has 30mA, doesn't matter if its a mobile connector or a house installation, and you may have those which are arbitrarily delayed, i.e. they do not trip after two periods.
I teach an advanced ele safety course here, I get somewhat annoyed at how they keep changing the "lethal" level of current this side of the pond. Sigh...what, are they testing that??? Who would volunteer to be a subject??

Quote:
Originally Posted by zinsula View Post
You could also use a Thermistor instead of a bridge. Pass Labs do that, AFAIK.
They also do not meet safety with bolted fault. However, once a GFI is there, no problem. In fact, once a GFI is there, you could conceivably use a 5 or 10 volt power zener pair in anti-series.

Quote:
Originally Posted by simon7000 View Post
John (N)

The neutral and ground are supposed to be bonded at building entrance, as you know.

Now a typical domestic electric panel will have a neutral bar and an optional ground bar.
Mine has one. But I can't speak for legacy equipment. I do know that I did have a 50 amp sub-panel where the option to connect neutral to box was there, ground was directly tied to the box. At the time, I had no clue why the option was there. Now I know that as a sub panel, you must break the neutral to box connection... If you do not, the ground conductor will be carrying neutral current all the way back to the main panel, that is a violation. Grounding conductors must carry no load current normally.


Quote:
Originally Posted by simon7000 View Post
As to the 6 volts permitted between neutral and safety ground. If more than even a few hundred millivolts is present the "safety" diodes begin to conduct! At 1.4 volts they will be close to their limit. As there is a limit on the 6 volts but not the current to produce the voltage, your diodes can fail even on an outlet that meets code.

ES
That's why Ive been discussing the bolted fault current and what diodes are capable of handling.

You mention 6 volts again...is that code somewhere? I recall a 50 volt code for voltage classification, but I don't recall 6.

j

Last edited by jneutron; 1st May 2012 at 03:42 PM.
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Old 1st May 2012, 04:04 PM   #22849
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Originally Posted by jneutron View Post
Mine has one. But I can't speak for legacy equipment. I do know that I did have a 50 amp sub-panel where the option to connect neutral to box was there, ground was directly tied to the box. At the time, I had no clue why the option was there. Now I know that as a sub panel, you must break the neutral to box connection... If you do not, the ground conductor will be carrying neutral current all the way back to the main panel, that is a violation. Grounding conductors must carry no load current normally.




That's why Ive been discussing the bolted fault current and what diodes are capable of handling.

You mention 6 volts again...is that code somewhere? I recall a 50 volt code for voltage classification, but I don't recall 6.

j
Welcome to my world! Most electricians isolated the safety ground buss from the box, as the neutral buss comes installed!

The six volts is from the test for ground conduction. You insert a 40 amp fuse in a hot leg and short it to ground. If the fuse blows the ground is good. Really! The code calls for 3 ohms or less. Then you look at the permitted unbalance current typically 10% for residential unit. So a 200 amp panel can have 20 amps or 6 volts!

ES
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Old 1st May 2012, 04:18 PM   #22850
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Originally Posted by simon7000 View Post
The code calls for 3 ohms or less. Then you look at the permitted unbalance current typically 10% for residential unit. So a 200 amp panel can have 20 amps or 6 volts!

ES
3 ohms for which? Residential earthing is 25 ohms max.

I times R = V

20 times 3 equals 60. (don't worry, my math is just as bad once the numbers are more than my finger total..)

Do you mean .3?

j
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