On Fri, 29 Apr 2005 21:25:17 UTC, "Sbharris[atsign]ix.netcom.com"
wrote:

What's in a name? Ahem, I called it a "service panel," and you two call
it a "service head," or a "cutout." But it's the same place in the
system.

Fine. But then it wasn't you I was disagreeing with.

--
Bob Eager
begin a new life...dump Windows!

On Fri, 29 Apr 2005 21:44:35 UTC, "Sbharris[atsign]ix.netcom.com"
wrote:

Look you simply don't understand the things completely. Rather than
argue with me, I recommend you educate yourself.

http://www.codecheck.com/gfci_principal.htm

The fact that he can't spell 'principle' rather reduces its
credibility...

--
Bob Eager
begin a new life...dump Windows!

YES!

wrote:
Look you simply don't understand the things completely. Rather than
argue with me, I recommend you educate yourself.

http://www.codecheck.com/gfci_=ADprincipal.htm



The fact that he can't spell 'principle' rather reduces its
credibility...

COMMENT:

[1] Since this isn't an essay on use of English, but a tutorial in
electrical engineering, I would say not.

[2] Actually, it's impossible to tell if he misspelled "principle"
unless you know that was the word he intended. For all you know, the
..htm file is is the principal one the author uses for explaining
GFCI's. =20

SBH

"Sbharris[atsign]ix.netcom.com" wrote in
ups.com:

Look you simply don't understand the things completely. Rather than
argue with me, I recommend you educate yourself.

Educate yourself.

Your explanation of how the RCD/GFI works "an RCD/GFI, ...places a small
voltage between neutral and ground ....The purpose of this small voltage is
so the RCD can detect a ground-neutral "fault"...." is wrong. Dead wrong.

The GFI does NOT depend on a voltage difference to sense the fault, it
depends on unbalanced current flow, as I said. See the current transformer
in the drawing in your reference?
http://www.codecheck.com/gfci_principal.htm

See the two current carrying wires going through the core? As long as the
current in those is equal, they cancel each other out and there is no
current induced in the secondary that feeds the 'sensor circuit'.

You gave dangerous advice when you said:

[quote]
..... But if the casing is connected to neutral at least, then you have
a chance that a hot wire contacting it will trip your fusebox, which is
a poor man's GFI.
[unquote]
even with the caveats you gave.

Never wire the neutral to the case.
Case to safety ground or be sure to float the case.

Neutral to case can kill you even with a GFI!!!!
1) If a hot case on one item and the neutral case on the other are plugged
into the same GFI protected circuit, there will be NO ground fault if you
contact both.

2) If a an old, non polar outlet is encountered or a miswired outlet (they
do happen) and 'neutral' is actually 'hot'

--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

"Sbharris[atsign]ix.netcom.com" wrote in
oups.com:

A GFCI works, in part, as you describe below.
In addition, it detects a ground/neutral short
as described at the following url:
http://www.codecheck.com/gfci_*principal.htm
I believe that function is what the poster was
referring to.

Correct. Modern GFI's really have two parts. The main one keeps you
from killing yourself, by cutting off current when you have a hot to
ground current. The active SECOND part (a second toroid) allows the
device to detect ground-neutral faults, so it can trip then, when its
sensing function has been compromised.

Look again. See the two wires going through the core? [ignore the test
line]

Each of those wires serves as the primary of a transformer.

As long as the SAME current flows in BOTH of those wires, they cancel each
other out. No current is induced into the secondary.

An imbalance in the current in those wires can be due to MORE current
flowing in EITHER of them than in the other.

An imbalance will trip the GFI.

Notice, there is NO second circuit to detect ground/neutral shorts. It is
an imbalance in current that trips the GFI.

The GFI depends on the current through BOTH wires being equal.




--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

bz wrote in
98.139:

Educate yourself.


My appologies. I read a bit further in the article and see the second
circuit. The GFIs I have taken apart did NOT have two torroids.

I was wrong. Sorry. Please accept my humble appology.

(I still think that connecting neutral to case is dangerous, however)



--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

"Bob Eager" wrote in message
...
On Fri, 29 Apr 2005 21:44:35 UTC, "Sbharris[atsign]ix.netcom.com"
wrote:

Look you simply don't understand the things completely. Rather than
argue with me, I recommend you educate yourself.

http://www.codecheck.com/gfci_principal.htm

The fact that he can't spell 'principle' rather reduces its
credibility...

VBG

Mary

--
Bob Eager

"Lars" wrote in message
...

Today I touched the outside of the lampshade and got a sort of
vey
mild tingle feeling which felt "odd". When I used a mains
tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the
Anglepoise
lamp was live.

Once had lots of problems like this, and when i got a shock off the
earth I did something about it. It turned out lots of the various earth
connections around the house were just copper cable twisted together,
so of course the joints had gone high R over time. Also the earth rod
was disconnected, so there was no E anywhere anyway. Just glad there
was no shower.


NT

bz wrote:
"Sbharris[atsign]ix.netcom.com" wrote in
oups.com:


A GFCI works, in part, as you describe below.

In addition, it detects a ground/neutral short
as described at the following url:
http://www.codecheck.com/gfci_*principal.htm
I believe that function is what the poster was
referring to.

Correct. Modern GFI's really have two parts. The main one keeps you
from killing yourself, by cutting off current when you have a hot to
ground current. The active SECOND part (a second toroid) allows the
device to detect ground-neutral faults, so it can trip then, when its
sensing function has been compromised.


Look again. See the two wires going through the core? [ignore the test
line]

Each of those wires serves as the primary of a transformer.

As long as the SAME current flows in BOTH of those wires, they cancel each
other out. No current is induced into the secondary.

An imbalance in the current in those wires can be due to MORE current
flowing in EITHER of them than in the other.

An imbalance will trip the GFI.

Notice, there is NO second circuit to detect ground/neutral shorts. It is
an imbalance in current that trips the GFI.

The GFI depends on the current through BOTH wires being equal.





He does not need to look again. He has it
right. Go read the url.

No one is disputing the imbalance detection.

The poster is discussing the *additional* circuitry
that is used to enable a GFI to detect a
downstream short between neutral and ground.

Ed

ehsjr wrote in news:aU_ce.3275$4v.1782@trndny03:

bz wrote:
"Sbharris[atsign]ix.netcom.com" wrote in
oups.com:


A GFCI works, in part, as you describe below.

In addition, it detects a ground/neutral short
as described at the following url:
http://www.codecheck.com/gfci_*principal.htm
I believe that function is what the poster was
referring to.

Correct. Modern GFI's really have two parts. The main one keeps you
from killing yourself, by cutting off current when you have a hot to
ground current. The active SECOND part (a second toroid) allows the
device to detect ground-neutral faults, so it can trip then, when its
sensing function has been compromised.


Look again. See the two wires going through the core? [ignore the test
line]

Each of those wires serves as the primary of a transformer.

As long as the SAME current flows in BOTH of those wires, they cancel
each other out. No current is induced into the secondary.

An imbalance in the current in those wires can be due to MORE current
flowing in EITHER of them than in the other.

An imbalance will trip the GFI.

Notice, there is NO second circuit to detect ground/neutral shorts. It
is an imbalance in current that trips the GFI.

The GFI depends on the current through BOTH wires being equal.





He does not need to look again. He has it
right. Go read the url.

No one is disputing the imbalance detection.

The poster is discussing the *additional* circuitry
that is used to enable a GFI to detect a
downstream short between neutral and ground.

You are correct.
I was wrong.

I missed seeing the other drawings, further down the page.
My mistake.



--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

Lars,
to check the leak resistance of mains circuits you need a special
"megger"meter.This is usually in the range of Mohms, so usually a normal
multimeter shows infinite resistance (sometimes modern digital ones are
capable of measuring this resistance).It's very dangerous to use something
that gives you (even) a slight shock.If you find it's too much money to have
it professionaly repaired (maybe a worn out cable that touches the frame?)
then better trash it, than put your life in danger.

--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "Lars" Ýãñáøå óôï ìÞíõìá
...
My electrical theory is fair but not great. Can someone please
advise me.

I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.

Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

I unplugged the lamp and tested the resistence between the live
pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result.

So the lamp seems ok. But something seems to be wrong!

QUESTION: Is my lamp safe to use and could I get a shock from it
in its present condition?

QUESTION: If my lamp is unsafe then is there a repair I can do?

Thank you for any info.
Lars

-----------------

PS: Picture of Anglepoise model 90:
http://www.anglepoise.com/timeline/model_90.jpg

Basically, Double insulated is a little misleading, but
in UL/CSA parlance, it means that the internal wiring
is such that it would take TWO faults to occur, either
of which would stop the product from working, before
anything could become electrically dangerous to the
user. Usage conditions are also taken into account.
Among other things it also means that there cannot
be any exposed metal on the product. ALL exposed metal
must be grounded, which become a non-essential in
double insulated products.

It also means it doesn't need a third "prong", and the
blades do not have to be polarized on the two-blade
plug, and it does not need a 3-hole outlet.

Pop


"Bill Woods" wrote in message
...
On Thu 28 Apr 2005 09:44:56, s--p--o--n--i--x wrote:


If it's the sort of anglepoise lamp I'm thinking of
it will be
double insulated.

What does "double insulated" mean in actual practice?


Whilst it would be sensible to earth the thing, it
will need
'cross bonding' across the hinged joints.

Bill Woods wrote:

What does "double insulated" mean in actual practice?

I guess its a derivative of the literal term. There are 2 layers of
insulation between live and metal casing or user, wire ends are cable
tied together so that if one comes out it doesnt wander far enough to
touch anything dangerous, and the insulation test v is much higher. No
earth connection is used.

Thats the meant-to. In practice there are plenty of [[]] products that
do not meet the above at all, japanese stereos and spotlights
especially.


NT

"Pop" wrote in message
...
Basically, Double insulated is a little misleading, but in UL/CSA
parlance, it means that the internal wiring is such that it would take TWO
faults to occur, either of which would stop the product from working,
before anything could become electrically dangerous to the user. Usage
conditions are also taken into account.
Among other things it also means that there cannot be any exposed metal
on the product. ALL exposed metal must be grounded, which become a
non-essential in double insulated products.

It also means it doesn't need a third "prong", and the blades do not have
to be polarized on the two-blade plug, and it does not need a 3-hole
outlet.


Not entirely true. The classic example is a double-insulated inexpensive
power drill. The chuck that holds the bit is metal, and is not grounded.
The tool does not have a third prong grounding conductor. But it meets the
definition of double-insulated because the chuck is insulated from the motor
by nylon gear-drive. And the windings on the motor are, of course,
insulated from the motor frame. So it would take two faults, just as you
said. It has no third prong, also as you said. But the exposed metal parts
are *not* necessarily grounded.

daestrom

wrote
On Sat, 14 May 2005 16:09:03 GMT, "daestrom" wrote:
SNIP
Not entirely true. The classic example is a double-insulated inexpensive
power drill. The chuck that holds the bit is metal, and is not grounded.
The tool does not have a third prong grounding conductor. But it meets
the
definition of double-insulated because the chuck is insulated from the
motor
by nylon gear-drive. And the windings on the motor are, of course,
insulated from the motor frame. So it would take two faults, just as you
said. It has no third prong, also as you said. But the exposed metal
parts
are *not* necessarily grounded.

daestrom


So they put in nylon gears, which we all know have a very limited life
span, instead of using reliable gears and adding a grounded cord.
That's just plain stupidity at it's worse. Also the reason I am
always looking for the old solid metal drills at garage sales. Not to
mention that most new drills have those keyless chucks, and I
absolutely despise those useless pieces of ****.

I'd much rather spend the extra dollar or two for the steel gears and
grounded cord.

I bought a portable jig saw (saber saw) 2 years ago. It had plastic
or nylon gears. I used it maybe 2 hours at most cutting plywood and
such. Then I inserted a metal cutting blade and started to cut a
piece of steel barn siding. I was cutting the length of the steel or
about 8 feet. That stuff is only 22 gauge or thereabouts. I cut
about 2 feet when the saw stopped cutting, but the motor was still
running. I opened the saw to find the nylon gears completely
stripped. After a big hassle, I was able to get the thing replaced
thru the warranty, but as far as I am concerned, it's pretty much a
useless tool, since I know as soon as I use it for anything more than
cutting some balsa wood, the new one will strip too. Just more
inferior crap sold by Black & Decker.

Mark

Nylon gears can last for decades of use when not abused. Jigsaws are not the
best choice for cutting 22 gauge steel. Tin snips or nibblers are a much
better choices. For a saw blade to work most efficiently, the material must
be significantly thicker than the pitch of the blade. When cutting thicker
material the teeth lower on the blade hold the saw away from the material
being cut. Without these lower teeth in contact, every time a tooth of your
saw hit caught on the bottom of the sheet-metal, it sent a major shock
straight up the transmission.

Maybe you have to buy the stuff not in the bargain bin. I like my old Black
and Decker drill, but if I ever start doing serious work, I would buy a new
one that is lighter more efficient and more powerful.

wrote:

Bill Woods wrote:


What does "double insulated" mean in actual practice?


I guess its a derivative of the literal term. There are 2 layers of
insulation between live and metal casing or user, wire ends are cable
tied together so that if one comes out it doesnt wander far enough to
touch anything dangerous, and the insulation test v is much higher. No
earth connection is used.

Thats the meant-to. In practice there are plenty of [[]] products that
do not meet the above at all, japanese stereos and spotlights
especially.


NT

Originally it meant a transformer with not only insulated wire, but an
actual sheet of something insulating between primary and secondary.
I think it then gort extended to the above specs.