From: chrisc@gold.gvg.tek.com (Chris Christensen)
Newsgroups: rec.audio.high-end
Subject: Re: house grounding
Date: 8 Sep 92 21:22:38 GMT
Organization: Grass Valley Group, Grass Valley, CA
Originator: tjk@csd4.csd.uwm.edu


In article <9209021557.AA02473@sonny.proteon.com> jas@proteon.com 
(John A. Shriver) writes:

>Aside from which, your house almost certainly already has a ground
>stake.  Well, most likely a ground pipe.  The cold water pipe coming
>into your house.  In my house (and per the National Electric Code),
>there is a substantial (8 guage?) bonding wire between the neutral bus
>of the breaker panel and the water pipe entering the house.

I believe that the NEC only specifies the minimum size of the saftey
ground wire and not the max size.  It may be easirer to install
multiple safety ground wires than one large one.

While you are beefing up the saftey ground wire think of installing a
UFER ground.

I said the same thing "what's a UFER ground".  A UFER ground is a
copper wire that is ran through the concrete footing of the house.  I
believe the minimum length was 12 feet of #6 or #8 copper wire.

The reasoning is, that a driven copper rod will corrode and loose it's
grip on the earth.  A UFER ground relies on the contact of the
concrete with the soil.  With a house sitting on the footing you are
pretty well guaranteed a gound.....

I have both!  I have not detected any problems with electrical
interference from appliances In my studio that would be conducted on the
grounds of the house.

I would suggest that if you are building a house ask the contractor to
wrap heavy guage copper wire around the reinforcing bar used in the
concrete.  Bring it up through the concrete stem wall as close as
possible to the service entrance. Hopefully your service entrance is
near the cornre of the footing so you can run a UFER ground  in both
directions of the corner.  Use seperate wites and clamp them the the
driven rod.  I put my driven ground rod in the footing also!

If you are pouring a concrete patio or other construction the
installation of a UFER grounding system to agument the existing saftey
ground could help add "mass" to your grounding system.

>I suppose one could legally (within the NEC) have that bonding wire
>made larger.  That would cut the bounce of the ground due to
>imbalanced neutral current.  The size of the holes in the netral bus
>bar could pose a size limit, however.

The use of multiple conductors should not be ruled out!

>I suppose one way to beat all the neutral noise and imbalance would be
>to put in a 220V outlet (hot-to-hot), and use 220V power amplifiers.
>That's going to halve the current drawn for a given power.  It's
>getting to the point where some of the high end Class A amps draw so
>much current that they almost have to be 220V.  (If it looks like a
>space heater, and feels like a space heater...)

I have said it before and I will say it again.  Have a sub pannel
installed at the equipment location.   Ask the electrician to install
a seperate heavy guage ground wire back to the house panel (same size
as current carrying wires)  Don't rely on the the metal conduit as the ground.
If the electrician is using metal conduit insist that a full size bare copper
wire also be pulled in for grounding!

If you have a modest system install a 30 amp sub panel with a breaker
for each power amp and a seperate one for preamp, tuner. CD etc.
Ground all devices to the service box.  If there is a ground loop
between any of the equipment then connect grounding bus bar and copper
braid to each of the chassis of the equipment. 

If you are lucky enough to have balanced I/O,  start the system design
with all of the pin 1 (ground connections)  made.  If there is a hum
problem start with the power amp and lift pin 1 *AT* the power amp connection.

Always maintain the saftey grounds and if a piece of equipment doesn't
have one consider installing a line cord that does!

Oh and if anything I have suggested is in violation of the NEC or
local regulations DON'T DO IT !!

I have operated large "portable" sound systems for years and for a lot
of those years I was treating the safety grounds as an enemy.  I would throw
on a ground lifter at the drop of a hat.

I finally got smart and I lift the pin 1 ground (balanced feed) at the amp
racks only and the system is hum free.

I used to have problems with different amps in the rack.  The amp that
I had for mids (tri-amp 2500 watt total system at the time) would buzz and the
rest would be reasonably quiet.

The amps that I use now and the way I use the balanced lines have
eliminated inter-rack hum and the system is very quiet!
-- 
Chris Christensen                  The opinions I express are my own,
chrisc@gold.gvg.tek.com            and sometimes they are wrong!
916-478-3419 FAX 916-478-3887      After all, I *AM* only human.
Newsgroups: rec.audio.high-end