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PostPosted: Sat Aug 15, 2009 2:40 am 
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Location: san francisco
wondering if anyone sees an issue with what i'm going to do.

my music outlets (on own leg, own circuit) will each have a dedicated wire running back to a sub panel in my studio. the sub will have it's own ground rod. the sub will have 3 #10 wires running back to the service main/panel connecting as you'd expect: leg 1, leg 2, nuetral/ground.

would this fullfill the star grounding requirements?

the other option is no subpanel, run all the lines out to the studio for main/service panel. 3 circuits and all the dedicated grounds. this means digging up the old underground conduit and installing 1" conduit. lots more work/money. and i'm not sure if it's necessary.

thoughts?

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room dimensions: free standing, floor 23'x17', roof slopes short distance (17') from 11'-8'. approx 100 year old sauna house. most framing 2x4, 24 OC. approx 3500 cu/ft.


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PostPosted: Sat Aug 15, 2009 3:18 am 
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Joined: Fri Jan 11, 2008 3:21 am
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Location: Cleveland, Ohio, USA
Nope. this will NOT be good, safe or legal!
You need 4 wires from the sub-panel to the main panel. Hot (A), Hot (B), Neutral (white) & Safety Ground (green).
In your room, you can run a Neutral (white) wire from each outlet to the sub-panel Neutral bus (which is insulated from the sub-panel chassis). You can also run a Safety Ground (green) wire from each outlet to the sub-panel Safety Ground bus which is chassis mounted. You can add a ground rod if you wish (if your room is in a different building like a garage you must add a ground rod). This ground rod is connected to the sub-panel Safety Ground bus, then to the main panel through the green wire. All ground rods in the system/building must be connected together at the main panel (bad things can happen during a thunderstorm if they aren't).

For lots more information see:

The Bill Whitlock of Jensen Transformers Seminar paper
http://www.jensen-transformers.com/an/g ... eminar.pdf

The Jim Brown of Audio Systems Group whit paper
"Power and Grounding for Audio and Audio/Video Systems"
http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf

"The TRUTH" from ExactPower of Middle Atlantic Products
http://www.exactpower.com/elite/wpapers.aspx

or a long version of the same paper

"Power White Paper" from Middle Atlantic.com
http://www.middleatlantic.com/power.htm

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PostPosted: Sat Aug 15, 2009 6:24 am 
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Location: san francisco
this is all done with conduit. doesn't the conduit act as safety ground?

i have those papers. but reading them is a bit confusing for me. they will probably make more sense after i have a better foundation.

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room dimensions: free standing, floor 23'x17', roof slopes short distance (17') from 11'-8'. approx 100 year old sauna house. most framing 2x4, 24 OC. approx 3500 cu/ft.


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PostPosted: Sun Aug 16, 2009 10:15 am 
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Location: Cleveland, Ohio, USA
Well you can use the EMT conduit for the only Safety Ground connection, but I wouldn't!

First re-read page 33 of the "Power White Paper", especially the part near:

"Conduit must be installed as a complete system before the wiring is installed. The conduit is considered a “grounding conductor”. A supplemental grounding conductor may be installed. For AV installations it is recommended to use an insulated ground wire when metallic conduit is required or specified."

Lots of people go to extra effort to isolate the Safety Ground to their A/V equipment from the conduit.

The "Power White Paper" and it's companion "The Truth" are both easy reads (being mostly drawing) and show the best ways to wire a A/V room.

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PostPosted: Sun Aug 16, 2009 10:35 am 
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Location: Cleveland, Ohio, USA
If you do add an auxiliary ground rod near your A/V room, I would definitely run a Safety Ground wire back to the main panel.

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PostPosted: Sat Aug 01, 2015 9:31 pm 
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Very good and informative exchange .. Thank you!


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PostPosted: Mon Oct 26, 2015 2:29 am 
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Joined: Sat Aug 01, 2015 9:06 pm
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Very good and informative exchange .. Thank you!


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