Electrical code Compliance - Connect earth ground to the negative pin on a 3 pins cord

Author

Connect earth ground to the negative pin on a 3 pins cord

someone92@hotmail.com

2005-06-17, 11:29 pm

Hi,
I was wondering if it's a good idea to connect the earth ground on a
3 pins cord directly to the negative pin. Someone asked me this
question because it want to reduce the background noise on 2 pins
guitar amplificator. So he replaced the 2pins cord with a 3pins and
connected ground to the negative pin. Before I wouldn't have thought
that it could be a bad idea, but I heard that very small difference of
potential between to connection (mV or even uV) can create a huge
amount of current and produce heat which could cause fire (I heard it
for audio studios grounding, never ground both ends). So I was
wondering if the earth ground and the negative wire are already
connected together in an house's electrical connections. Should a small
resistor be connected between the 2 wires to prevent any problem? If it
can be done without any problems, why aren't they already connected and
used with 2 pins cord? Should the ground be used only to connect to the
appliance's casing to prevent shock hazard?

Thanks in advance, any suggestions are welcome too.

phil-news-nospam@ipal.net

2005-06-17, 11:29 pm

On 26 Mar 2005 19:23:08 -0800 someone92@hotmail.com wrote:

| I was wondering if it's a good idea to connect the earth ground on a
| 3 pins cord directly to the negative pin. Someone asked me this
| question because it want to reduce the background noise on 2 pins
| guitar amplificator. So he replaced the 2pins cord with a 3pins and
| connected ground to the negative pin. Before I wouldn't have thought
| that it could be a bad idea, but I heard that very small difference of
| potential between to connection (mV or even uV) can create a huge
| amount of current and produce heat which could cause fire (I heard it
| for audio studios grounding, never ground both ends). So I was
| wondering if the earth ground and the negative wire are already
| connected together in an house's electrical connections. Should a small
| resistor be connected between the 2 wires to prevent any problem? If it
| can be done without any problems, why aren't they already connected and
| used with 2 pins cord? Should the ground be used only to connect to the
| appliance's casing to prevent shock hazard?

It is less safe to do that. I would call that a bad idea.

I would suggest visiting the following web site and considering one of
these balanced power solutions to reduce hum:

http://www.equitech.com/

If you are using split single phase power, e.g. 120 volts in the USA,
AND your amp can be wired to accept 240 volts instead, AND you can get
240 volts in a 120 volt location (it will be balanced power), that might
be a cheaper alternate solution (but be careful that things are wired
the right way to accept that voltage).

--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------

someone92@hotmail.com

2005-06-17, 11:29 pm

quote:

> It is less safe to do that. I would call that a bad idea.

Are you talking about wiring ground to negative? or ground to casing?
If you are talking about ground to negative, why is it a bad idea? is
it because of what I was thinking about the difference in potential
which could occur and cause excessive current or another reason? If
it's about the casing I don't understand why because I know that about
every appliances metal casings are wired to ground to prevent shock
hasard.

Thanks

R.Lewis

2005-06-17, 11:29 pm

<someone92@hotmail.com> wrote in message
news:1111908116.461534.268100@o13g2000cwo.googlegroups.com...

quote:

>
>
> Are you talking about wiring ground to negative? or ground to casing?
> If you are talking about ground to negative, why is it a bad idea? is
> it because of what I was thinking about the difference in potential
> which could occur and cause excessive current or another reason? If
> it's about the casing I don't understand why because I know that about
> every appliances metal casings are wired to ground to prevent shock
> hasard.
>
> Thanks
>

Since you have no idea of what you are involved with do not touch anything -
you are only likely to electrocute someone.
Don't be silly.

phil-news-nospam@ipal.net

2005-06-17, 11:29 pm

On 26 Mar 2005 23:21:56 -0800 someone92@hotmail.com wrote:

|> It is less safe to do that. I would call that a bad idea.
|
| Are you talking about wiring ground to negative? or ground to casing?
| If you are talking about ground to negative, why is it a bad idea? is
| it because of what I was thinking about the difference in potential
| which could occur and cause excessive current or another reason? If
| it's about the casing I don't understand why because I know that about
| every appliances metal casings are wired to ground to prevent shock
| hasard.

Ground to casing is a normal connection. A separate ground wire is
intended for such purposes.

Connecting the ground wire to EITHER current carrying conductor is not
safe, violates the code (except for the required single bonding between
the neutral wire and ground at the power service entrance).

The term "negative" is not valid for AC power. There are terms "neutral"
and "grounded conductor" (note the "ed" at end distinguishing it from the
term "grounding conductor"). The further away a circuit connection is from
the main service entrance, the more voltage difference that can exist
between the groundING wire and the groundED wire.

When circuits are out of balance, current does flow on the neutral wire.
That's normal. Connecting the grounding wire to the neutral wire will
result in half of that current now flowing in the grounding wire and
energizing _everything_ in the building that has it's casing connected
to the grounding wire. This must absolutely be avoided.

Tell me what country you are in so I know what kind of electrical system
you actually have, so I won't confuse you with a multitude of explanations
trying to cover all other possibilities that don't apply to you.

--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------

someone92@hotmail.com

2005-06-17, 11:29 pm

Thanks a lot Phil for the very good explaination. I'm in Canada which I
think use the same electrical system as in the United States. So
exessive heating cannot be a fire hazard?

Roy Q.T.

2005-06-17, 11:29 pm

I don't think you're equipment will flame-up unless you're playing a
fiery tune};-) but if your so concerned with the heat from your amp get
a few muffin fans and install them over the ventilation slots.
Roy

phil-news-nospam@ipal.net

2005-06-17, 11:30 pm

On 27 Mar 2005 15:58:32 -0800 someone92@hotmail.com wrote:

| Thanks a lot Phil for the very good explaination. I'm in Canada which I
| think use the same electrical system as in the United States. So
| exessive heating cannot be a fire hazard?

Excessive heating would be beyond what the equipment is rated for. It
can be any number of hazards because it can start with destruction of
the equipment involved, and subsequently shorting things out, blowing
stuff up, and things too dangerous even for real-life TV. YMMV

--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------

BigWallop

2005-06-17, 11:30 pm

<someone92@hotmail.com> wrote in message
news:1111893788.276214.324160@o13g2000cwo.googlegroups.com...

quote:

> Hi,
> I was wondering if it's a good idea to connect the earth ground on a
> 3 pins cord directly to the negative pin. Someone asked me this
> question because it want to reduce the background noise on 2 pins
> guitar amplificator. So he replaced the 2pins cord with a 3pins and
> connected ground to the negative pin. Before I wouldn't have thought
> that it could be a bad idea, but I heard that very small difference of
> potential between to connection (mV or even uV) can create a huge
> amount of current and produce heat which could cause fire (I heard it
> for audio studios grounding, never ground both ends). So I was
> wondering if the earth ground and the negative wire are already
> connected together in an house's electrical connections. Should a small
> resistor be connected between the 2 wires to prevent any problem? If it
> can be done without any problems, why aren't they already connected and
> used with 2 pins cord? Should the ground be used only to connect to the
> appliance's casing to prevent shock hazard?
>
> Thanks in advance, any suggestions are welcome too.
>

Never, ever, connect the earth fault conductor to any of the phase carrying
conductors. Or, more simply, don't connect the earth to the neutral, ever.

Earth connections are used to take, or make, over current caused by short
circuit in the wiring, or from faulty equipment, and take the fault away
from the scene of the crime, and safely break the circuit so no one is
electrocuted. The earth wiring is properly called an earth fault conductor,
and is used to reduce risk of anyone coming in to contact with a live piece
of equipment, be it from the live conductor, or the neutral wires. Don't do
it !!!

No amount of connections between the neutral and earth conductors will take
away mains frequency buzzing (hummmm) from audio or video equipment. In
such cases, a balanced mains supply should be used to keep the audio/video
appliances separated from the direct mains supply. Using a transformer with
built-in "line noise suppression" is usually the best method for mains hum
reduction.

Roy Q.T.

2005-06-17, 11:30 pm

I have to review the NEC for Non or Commercial Entertainment
Equipment....

so', what if the guy makes a go between module of some electronic kind
and got it to abate the hazard converting it to a funny or useful
energetic exchange like other harmless lights or sounds effects.

The Idea of a Bonded Electrical System is that It Must stay Isolated
within the System or Equipment

but what if one Wore Rubber Gloves to Play it };-) could you over look
the Hot Neutral or Exposed Equipment ???? if on an Isolated Platform
would it still be that dangerous ? perhaps because it transmutes to the
entire building neutral system & in the case of thrid prong/neutral or
hot the third prong would energize the euipment ground & metal
interconnections of the Wiring system through out the whole electrical
system that serves it as a source.

So to Comply, Doon't do it };-) and if you do ?????? wear rubber gloves
(or don't touch anything else) and post Shock Hazard Signs ??? teheehee.

Don't Forget Harmonics :-) If The System is Shunted Right the Humm could
attract Others to it :-) How about a module inside a guitar suppling
each Guitar Cord with a different voltage ??? when they touched
together it spark real cool like :-o (my patent exome12943331 or pop or
something like that;)

Who dun That ?

Increase the voltage Doc:-)

Buttttttt> be safe and don't forget my check :-)

=AEoy

Andrew Thomas

2005-06-17, 11:31 pm

BigWallop wrote:

quote:

> <someone92@hotmail.com> wrote in message
> news:1111893788.276214.324160@o13g2000cwo.googlegroups.com...
>
>
>
> Never, ever, connect the earth fault conductor to any of the phase carrying
> conductors. Or, more simply, don't connect the earth to the neutral, ever.
>
> Earth connections are used to take, or make, over current caused by short
> circuit in the wiring, or from faulty equipment, and take the fault away
> from the scene of the crime, and safely break the circuit so no one is
> electrocuted. The earth wiring is properly called an earth fault conductor,
> and is used to reduce risk of anyone coming in to contact with a live piece
> of equipment, be it from the live conductor, or the neutral wires. Don't do
> it !!!
>
> No amount of connections between the neutral and earth conductors will take
> away mains frequency buzzing (hummmm) from audio or video equipment. In
> such cases, a balanced mains supply should be used to keep the audio/video
> appliances separated from the direct mains supply. Using a transformer with
> built-in "line noise suppression" is usually the best method for mains hum
> reduction.
>
>

I've tried the noise-supression isolation transformer approach and it
didn't work for me, though I'm determined to try it again.

I used to repair amps for a living. I assume the poster is talking about
a tube amp. The problem with old tube amps is that the metal chassis is
used throughout the amp as a convenient signal ground point, although in
most cases only the transformer secondary is grounded (in some cases it
is a "hot chassis" desing similar to old TV sets). This is generally
not done in modern equipment. It is quite probable that sucessfully
reducing noise in this type of equipment would involve installing an
isolated bus bar and tying all the signal grounds (typically a dozen or
more) to it. You would also have to replace the 1/4" input jacks with
isolated (ie: plastic body or plastic bushing) jacks, which are not hard
to find. Then the metal chassis could be grounded without essentially
tying it to neutral. Going further, the input jacks should be replaced
with XLR jacka, as should those on the guitar. Finally, any
connection(s) between the pickup(s) and the strings should be opened,
and the strings should be grounded via the dedicated ground on the XLR
jack.

It should be noted that modified or not, these amps are such a common
source of uncomfortable shocks that most musicians take them for granted
and the show goes on: the musician simply learns through trial and error
not to touch the microphone while strumming the guitar, for example.
While in many cases these undesirable currents are due to defective or
ill-conceived noise reduction schemes (ie: tying one or both AC line to
the chassis through a capacitor) oftentimes it is much more serious and
they live only by the graces of their gods. Electrocution resulting in
death is more common in the garage band "industry" than most.

-Andrew

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