| Author |
Message |
Vidar Løkken
Guest
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 Posted:
Mon Jun 13, 2005 8:17 pm Post subject:
Re: Power Strip Causing Ground Loop? |
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Arny Krueger wrote:
| Quote: |
According to several references, GFCI designed for personnel
protection will trip when leakage current exceeds 5
milliamps.
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Yep, which is _far_ from 70µA. But in Norway, the norm is 30mA. However,
Norway has a IT-net, not a TN-net. (Or was it TT? Never remember the
difference :P)
--
MVH,
Vidar
www.bitsex.net
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Steve Urbach
Guest
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| Posted:
Mon Jun 13, 2005 8:21 pm Post subject:
Re: Power Strip Causing Ground Loop? |
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On Mon, 13 Jun 2005 14:54:01 +0300, "Dimitrios Tzortzakakis"
<dimtzort@otenet.gr> wrote:
| Quote: | If that happens, then why does not my GFCI breaker trip?
--
1) the leakage current is below the GFIC trip threshold (this is |
likely, as the threshold would be set to prevent 'nuisance trips)
2) the GFIC breaker is defective or improperly installed.
3) You are not plugged into the circuit protected by the GFIC breaker
, _
, | \ MKA: Steve Urbach
, | )erek No JUNK in my email please
, ____|_/ragonsclaw dragonsclawJUNK@JUNKmindspring.com
, / / / Running United Devices "Cure For Cancer" Project 24/7 Have you helped? http://www.grid.org |
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Arny Krueger
Guest
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| Posted:
Mon Jun 13, 2005 8:34 pm Post subject:
Re: Power Strip Causing Ground Loop? |
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Vidar Løkken wrote:
| Quote: | Arny Krueger wrote:
According to several references, GFCI designed for
personnel
protection will trip when leakage current exceeds 5
milliamps.
Yep, which is _far_ from 70µA. But in Norway, the norm is
30mA. |
In the US - we consider 30 ma to be the limit for protecting
equipment. The threshold for protecting personel is 5 ma. |
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Vidar Løkken
Guest
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| Posted:
Mon Jun 13, 2005 8:50 pm Post subject:
Re: Power Strip Causing Ground Loop? |
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Arny Krueger wrote:
| Quote: | Yep, which is _far_ from 70µA. But in Norway, the norm is
30mA.
In the US - we consider 30 ma to be the limit for protecting
equipment. The threshold for protecting personel is 5 ma.
|
Yep, which relates back to that in a IT-net you have insulation between
the midpoint in xmfr and gnd, that also limits the current, while in the
US you have a TN net where gnd is connected straight to the mid-point.
Don't ask me to explain the differences, I only know that the norwegian
system is considdered safer, and there's two countries that is using it.
Norway and Peru or something like that.
So we have 2 wires, with a potential to each other of 220V, both being
"hot" relative to gnd.
Perphaps someone else in here can explain the difference between a IT
and a TN/TT net?
--
MVH,
Vidar
www.bitsex.net |
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Arny Krueger
Guest
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| Posted:
Mon Jun 13, 2005 10:06 pm Post subject:
Re: Power Strip Causing Ground Loop? |
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Vidar Løkken wrote:
| Quote: | Arny Krueger wrote:
Yep, which is _far_ from 70µA. But in Norway, the norm
is
30mA.
In the US - we consider 30 ma to be the limit for
protecting
equipment. The threshold for protecting personel is 5 ma.
Yep, which relates back to that in a IT-net you have
insulation
between the midpoint in xmfr and gnd, that also limits the
current,
while in the US you have a TN net where gnd is connected
straight to
the mid-point.
|
See reference, below.
| Quote: | Don't ask me to explain the differences, I only know
that the norwegian system is considdered safer, and
there's two
countries that is using it. Norway and Peru or something
like that.
So we have 2 wires, with a potential to each other of
220V, both being
"hot" relative to gnd.
Perphaps someone else in here can explain the difference
between a IT
and a TN/TT net?
|
http://www.mikeholt.com/documents/mojofiles/electricalearthingworldwide.pdf
pp 7-8 |
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Vidar Løkken
Guest
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| Posted:
Mon Jun 13, 2005 10:31 pm Post subject:
Re: Power Strip Causing Ground Loop? |
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Arny Krueger wrote:
| Quote: | http://www.mikeholt.com/documents/mojofiles/electricalearthingworldwide.pdf
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Thanks a lot :) That was a quite informative pdf, actually I should've
remembered my electrical installations book was 2 meter from me...
Thought I'd sold that book after last year, but anyway, that PDF
described it better than the book!
I had a peek at the rest...:)
--
MVH,
Vidar
www.bitsex.net |
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Kitchen Man
Guest
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| Posted:
Tue Jun 14, 2005 4:44 am Post subject:
Re: Power Strip Causing Ground Loop? |
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On Sun, 12 Jun 2005 21:33:53 -0500, Jim Adney <jadney@vwtype3.org>
wrote:
| Quote: | Sure, it's 60V as seen on a 10 MOhm meter, but the source impedance is
on the order of a MegOhm. That's never going to provide enough current
to be dangerous. Of course that assumes that all his components remain
in good condition. If something actually fails, then you're right and
he is without a safety ground.
|
Right on both points. It's that pesky second point that bothers me.
In addition, that small but probably continuous current could be
damaging to sensitive components; remember we're dealing with a
computer and a cable modem here, lots of low voltage, low current,
high speed "stuff" that could be damaged by strong transients.
An interesting but flawed solution is to connect the power strip
"ground" to the shield of the modem. That would give the strip a
return reference, but one fraught with difficulty on a number of
levels - power currents injected into an RF shield being the most
conspicuous. I don't like it. I'd get an electrician.
--
Al Brennan
"If you only knew the magnificence of the 3, 6 and 9,
then you would have a key to the universe." Nicola Tesla |
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Dimitrios Tzortzakakis
Guest
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| Posted:
Tue Jun 14, 2005 4:55 pm Post subject:
Re: Power Strip Causing Ground Loop? |
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--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "Steve Urbach" <dragonsclaw@NOTmindspring.com> ?????? ??? ??????
news:3m8ra11l2gg8j42d0vdnlcboime7mgi63t@4ax.com...
| Quote: | On Mon, 13 Jun 2005 14:54:01 +0300, "Dimitrios Tzortzakakis"
dimtzort@otenet.gr> wrote:
If that happens, then why does not my GFCI breaker trip?
--
1) the leakage current is below the GFIC trip threshold (this is
likely, as the threshold would be set to prevent 'nuisance trips)
The threshold in europe is always 30 mA.
2) the GFIC breaker is defective or improperly installed.
It's a new Siemens GFCI breaker I installed myself, and I hope I can install |
one correctly.
| Quote: | 3) You are not plugged into the circuit protected by the GFIC breaker
, _
The breaker protects my whole house.
, | \ MKA: Steve Urbach
, | )erek No JUNK in my email please
, ____|_/ragonsclaw dragonsclawJUNK@JUNKmindspring.com
, / / / Running United Devices "Cure For Cancer" Project 24/7
Have you helped? http://www.grid.org |
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Steve Urbach
Guest
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| Posted:
Tue Jun 14, 2005 9:18 pm Post subject:
Re: Power Strip Causing Ground Loop? |
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On Tue, 14 Jun 2005 14:55:33 +0300, "Dimitrios Tzortzakakis"
<dimtzort@otenet.gr> wrote:
| Quote: | The breaker protects my whole house.
Ah! |
the difference between international systems.
The US residential mainly requires only certain Branch circuits to be
GFIC (and now ARC fault) protected. Newer 'Industrial' systems have
the "whole" service panel version.
, _
, | \ MKA: Steve Urbach
, | )erek No JUNK in my email please
, ____|_/ragonsclaw dragonsclawJUNK@JUNKmindspring.com
, / / / Running United Devices "Cure For Cancer" Project 24/7 Have you helped? http://www.grid.org |
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lon
Guest
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| Posted:
Sun Jun 19, 2005 4:45 am Post subject:
Re: Power Strip Causing Ground Loop? |
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Get an outlet tester. They plug into the outlet and let you know if it is
wired correctly.
I believe you will find that you have an outlet with the neutral and hot
reversed.
How is your internet connection? In my experience this can cause wicked
packet loss.
"Howard Knight" <howardkinsd@yaEXPUNGEhoo.com> wrote in message
news:11ak23tensjvm95@corp.supernews.com...
| Quote: | First, let me tell you that I'm a retard when it comes to electronic
stuff. Anyway...
I was fiddling around behind my computer and got a nice shock. I'm
trying to figure out this problem and am hoping you folks could
help me out.
I get the shock when I touch any part of the back of my computer or
wires, and also touch the metal part of the cable that comes in and
connects to my cable modem. Here's the deal:
I live in an older house that is not grounded. The ground prong on
the outlets isn't connected to ground or anything else. Also, I've
determined that the coax cable coming in to my cable modem is
grounded. Somthing seems to be making the ground prong on my outlet
hot. I've narrowed down the problem to my power strip. I've
unplugged everything from my outlet and I check the outlet for
voltage. Neutral to hot gives me 110V. Neutral to ground give me
nothing (actually, for some odd reason, there does seem to be a
slight voltage (less than 2V). Hot to ground also gives me nothing.
As one would expect.
Now, if I plug in a power strip and do the same check on one of the
outlets on the power strip, I get: neutral to hot 110V, neutral to
ground around 60V and hot to ground around 60V. Is this right?
I've checked this with two power strips and I get the same results.
What would cause this? Is the polarity on my outlet wrong? Or,
am I just a dummy and am misintepreting what is going on. This
misterious 60V is what give me the shock.
Howard |
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