grounding 120v wall outlets

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grounding 120v wall outlets

Postby archive » Thu Apr 01, 2004 12:24 am

From: "David Quave" <dquave@b...>
Date: Sat Feb 10, 2001 1:27 pm
Subject: grounding 120v wall outlets

I have 10 foot grounding rods for each wall outlet in the studio. The ground
rods will be installed under the slab before it is poored.They will only be
used for the 120v outlets.I will use these for the equipment groundon the
third grounding insert instead of the bare copper wire going back to the
service panel intrance.In other words I will not be using the third bare
wire of the romex wire and instead go straight to the grounding rods from
each outlet.Is this going to be beneficial in preventing ground loops or is
this type of installation dangerous?One outlet will be used for all
equipment that is connected together,such as where the mixing console is
plugged in.I understand all that type of info on this subject,but I am
getting different opinions on this grounding setup. Is it better to just use
the third bare wire and go back to the main service entrance grounding buss
instead of individually grounding each outlet?
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Postby archive » Thu Apr 01, 2004 12:24 am

From: BASSMANCP@A...
Date: Sat Feb 10, 2001 2:18 pm
Subject: Re: [acoustics] grounding 120v wall outlets

In a message dated 2/10/01 8:25:28 AM Eastern Standard Time,
dquave@b... writes:

<< I have 10 foot grounding rods for each wall outlet in the studio. The
ground
rods will be installed under the slab before it is poored.They will only be
used for the 120v outlets.I will use these for the equipment groundon the
third grounding insert instead of the bare copper wire going back to the
service panel intrance.In other words I will not be using the third bare
wire of the romex wire and instead go straight to the grounding rods from
each outlet.Is this going to be beneficial in preventing ground loops or is
this type of installation dangerous?One outlet will be used for all
equipment that is connected together,such as where the mixing console is
plugged in.I understand all that type of info on this subject,but I am
getting different opinions on this grounding setup. Is it better to just use
the third bare wire and go back to the main service entrance grounding buss
instead of individually grounding each outlet?
>>

Isn't it better to have all studio outlets going to one point? If you
really
get picky, shouldn't all ground leads going to that (star point) be the same
length in order to keep the resistance's induced by the wire the same at
each outlet? Thus making all the gear sit at the same ground potential.

Best Regards
Chris Preston
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Postby archive » Thu Apr 01, 2004 12:28 am

From: "Jack Hildwine" <jackhildwine@u...>
Date: Sun Feb 11, 2001 12:02 am
Subject: Re: [acoustics] grounding 120v wall outlets

David,

You might want to talk with a knowledgeable electrician
or consult the NEC, especially if you are subject to a code
inspection for this work. It's my understanding that the
third wire safety ground must be bonded to the neutral at
the service entrance panel. Another good reference source is
Giddings' "Audio Systems Design and Installation".

Jack Hildwine
Gilbert, AZ
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Postby archive » Thu Apr 01, 2004 12:28 am

From: "Ty Ford" <tford@j...>
Date: Sun Feb 10, 1991 2:44 pm
Subject: Re: [acoustics] grounding 120v wall outlets

>David,
>
> You might want to talk with a knowledgeable electrician
>or consult the NEC, especially if you are subject to a code
>inspection for this work. It's my understanding that the
>third wire safety ground must be bonded to the neutral at
>the service entrance panel. Another good reference source is
>Giddings' "Audio Systems Design and Installation".
>
>Jack Hildwine
>Gilbert, AZ

Sorry, just popped in on this one. You're using a star ground system, right?
The ground from each receptacle comes together at a common point (center of
the star) and a big cable connects from there to the electrical system ground.

Star grounding is the best way to eliminate ground loops caused by
"voltage-to-ground" differences that inevitably occur between receptacles
that are wired in parallel.

Regards,

Ty Ford

Ty Ford's audio equipment reviews and V/O sound files can be accessed at
http://www.jagunet.com/~tford
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Postby archive » Thu Apr 01, 2004 12:30 am

From: "Danny Stinnett" <danny@p...>
Date: Sun Feb 11, 2001 2:05 am
Subject: Re: [acoustics] grounding 120v wall outlets

Hi FWIW, this is what I did...just setup 3 20 amp circuits for studio and
left the ground wires real long. Then I ran those ground wires to my main
ground rod. This has been very quiet...except for when we are micing my
buddys' '52 tele.!! <VBG> Danny
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Postby archive » Thu Apr 01, 2004 12:31 am

From: Stephen Foster <oncourse@i...>
Date: Sun Feb 11, 2001 4:19 am
Subject: Re: [acoustics] grounding 120v wall outlets

I did the same in a studio once, and it worked like a dream there too. All
the ground wires were the same length, and we connected them all to the
copper pipe coming in from an old heating oil tank out in the back yard.
Talk about the ground rod from hell....

BTW... Teles don't sound good without SOME buzz... Just so they don't buzz
louder than the drums. *S*

sf
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Postby archive » Thu Apr 01, 2004 12:32 am

From: "Danny Stinnett" <danny@p...>
Date: Sun Feb 11, 2001 6:26 am
Subject: Re: [acoustics] grounding 120v wall outlets

Stephen, Yeah His tele sounds so good you can put up with a little buzz!!
Danny
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Postby archive » Thu Apr 01, 2004 12:33 am

From: Bill Thompson <Bill@A...>
Date: Sun Feb 11, 2001 5:57 am
Subject: Re: [acoustics] grounding 120v wall outlets

Hi David,

As many have mentioned, the individual ground rods are an all around bad idea!

1) from a noise perspective, you've just created ground loops... lots of them.
This would be an almost impossible situation to troubleshoot!!!

2) It is not safe! Granted, in a studio it seems unlikely that you could cause
enough current to flow through ground, or a large enough potential difference
between any two points... but the thing is, it is only unlikely... it is not
impossible! Do you really want to take the chance? You would be quite literally
playing with your life.

3) At least in the US that would never pass an electrical inspection.

There are a couple of right ways to do this... naturally<G>:

My personal favorite is to use isolated outlets and run individual insulated
ground wires back to the service entrance. I also put in a separate buss bar
that
I then bonded to the existing earth ground, but that was more for neatness than
anything else, though one could make an argument that it could help.

There are other issues to consider as well, including isolation, differential
power distribution, line filters, etc. One real noise buster I like is to run
the
large devices (console, amplifiers, tape decks, etc) from a 220VAC source if
their
transformers have the proper taps.

I'm also a big fan of low voltage distribution for rack gear (a concept that was
once championed by RANE, but never really gained popularity.)

Two books that are quite detailed on all of this are Philip Giddings Sound
System
Installation and Philip Newell's Project Studios. In addition, there is a great
app note at Rane's web site, and a couple of decent papers at both Equi-tech and
Furman. For the dissenting view on differential power check Jensen Transformers
site.

Good luck,

Bill
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Postby archive » Thu Apr 01, 2004 12:38 am

From: SRF7@a...
Date: Sun Feb 11, 2001 2:52 pm
Subject: Re: [acoustics] grounding 120v wall outlets

In a message dated 2/10/01 8:25:33 AM Eastern Standard Time,
dquave@b... writes:

> I understand all that type of info on this subject, but I am
> getting different opinions on this grounding setup. Is it better to just use
> the third bare wire and go back to the main service entrance grounding buss
> instead of individually grounding each outlet?

What you describe (separate grounding for each outlet) would fail inspection
here in FL.

The explanation I got was that multiple grounds would create the potential
for a voltage differential between the grounds serving two different live
circuits and therefore an electrocution hazard (I'm hold my home made Strat
copy while pointing to the B string on your vintage Les Paul to better
describe the "new" chord I found .... and the circuit powering your amp has a
better path to ground than the circuit powering my cheesy old amp ... ZAP! .

As a practical matter this seems pretty far fetched to me ... provided all
the grounds are properly attached (how big could the difference be?). ... but
there it is. For example ... by local code if you feed a separate building
from an existing service on an existing building, you MUST install a new
ground in the new building ... So the rule works out to: even if in fed
from a common main, every building must have one and only one ground ... you
can't run the new building off the ground in the existing building ... but
you also can't run a new ground for a new circuit within the existing
building ... go figure.

That said, what I did was run surface mount EMT (metal conduit) to a single
ground just like code says. I figured if I had problems I could pull more
wire (after the inspector was gone) and come up with a solution (star
grounding perhaps, or maybe a power conditioner for the audio circuits).
Happily no such jiggery pokery was necessary ... everything works great.

Good Luck

Scott R. Foster
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Postby archive » Thu Apr 01, 2004 12:51 am

From: Dan Nelson <drnelson@s...>
Date: Mon Feb 12, 2001 8:22 pm
Subject: Re: [acoustics] grounding 120v wall outlets

I don't believe this will meet code, be very safe and might cause ground loops.
Unless all the ground rods are connected together with a heavy wire you will
most like see a potential between them which will cause ground loops and if it
is large enough a shock hazard.

I feel it is better to run each circuit back to the main panel and install the
best ground you can there. Normal house wiring with romax is almost the same as
isolated ground if you install it that way and without splices. I use 12 gauge
instead 14 on the 15 amp circuits

Dan
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Postby archive » Thu Apr 01, 2004 12:52 am

From: Bill Thompson <Bill@A...>
Date: Tue Feb 13, 2001 12:18 am
Subject: Re: [acoustics] grounding 120v wall outlets

Hi Dan,

You are quite correct about the code, safety, and loop issues! The Romex
comment is
good too, but you might want to be more specific, just to be safe<G>! (And it
is a
very clever idea!!)

It is my understanding that isolated grounds are OK according to the National
Electrical Code, but I am not a licensed electrician (my licensed electrician
and
inspector agreed FWIW). If you are going to approximate isolated grounds using
regular Romex you must make every path between outlet and service entrance a
direct
path. You also have to use plastic utility boxes, and be careful not to nick the
cable jacket.

Out of laziness, I opted for daisy-chained hotand neutral conductors, and
home-run
grounds with an separate, insulated wire. I would not do that again. I might
still
use the insulated ground wire, but the daisy-chained neutral did cause me
problems
with some of my gear. For the additional cost of a little wire, and the
additional
space in the breaker panel, I'll run the extra runs. My next place will also
have
all the computers, midi gear, and tape decks in an equipment room, so I won't
have
outlets spread out all over the place either.

It never ceases to amaze me the little things that can get you! Of course years
ago
we were fighting the 60-70dB S/N ratio of 2 inch tape machines, today the
challenge
is much greater.

Bill
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