Help needed in finalizing my Star Grounding Plan

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studio1670
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Location: San Jose, CA
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Help needed in finalizing my Star Grounding Plan

Post by studio1670 »

Hello all,

I am trying to complete my Star Grounding plan for my home studio and I need some final questions answered before I can go any further. First, here are the details of my setup.

This is a home studio, meaning, that it is in a residential house that I live in. My studio is on the second floor of the house. It consists of a control room (bedroom), live room (loft at the top of the stairs) and a tracking room (another bedroom).

All of the electrical service currently used, is the normal wiring that the house was originally wired with (14 gauge with 15 amp breakers in the power panel on the first floor). The two bedrooms are on one breaker, and the loft is on another breaker. The house is 9 years old and I currently don't have noticable problems with interference from the furnace, refridgerator, lights, ect.

I have experienced the 60 cycle hum when connecting gear from 2 different rooms together, so I have decided to do a star grounding system for these 3 rooms.

So far, my plan is to run 1 new outlet for each room. Each one with a home run back to the panel (12/2 romex and using plastic recepticle boxes). All the existing power to the rooms will stay. I will use the one outlet in each room for anything related to the studio.

I also plan to add 1 tandem breaker (only 1 slot open right now) to my power panel to support these outlets. The tandem breaker will be 20/20. The control room will get it's own circuit and the loft and other bedroom will share the other circuit. The control room will have a higher current draw due to the outboard racks, computer, monitors, amps, ect.

I have read the star grounding sticky several times along with many other threads on this site and other sites. I have also read Jim Brown's paper entitled "Power and Grounding for Audio and Video Systems".

Between all these resources I think I have a pretty good idea of how this works but I need a couple detailed questions answered:

1. How to connect the neutral and ground home runs in the power panel. Remember this power panel is the main one in my house that was installed when the house was built. Do I connect them to the existing busses? Do I need to install a seperate isolated ground bus, and then connect that to the ground bus in the panel?

2. How can I calculate if one 20 Amp circuit is enough power for my control room? I have added up all the wattage requirements for all the gear I currently have, and it adds up to 3400 watts (a 20 amp circuit can deliver 2400). I believe that these ratings for the gear are MAX wattage and not average wattage. Is there a standard formula to use to estimate this? 50% of max rating for example? Right now, all my gear, lights, ceiling fan plus the other bedroom lights, ceiling fan and outlets all share a 15 amp circuit and I have never blown a breaker. I figured a 20 amp circuit for gear only in the control room would be plenty, but I don't want to do this project twice.

Thanks,
Mike
Speedskater
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Joined: Fri Jan 11, 2008 3:21 am
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Re: Help needed in finalizing my Star Grounding Plan

Post by Speedskater »

Mike,

If it works on a 15 Amp breaker with additional loads, then it better work on a 20 Amp breaker all by itself!

In a main breaker box all the Neutrals and Safety Grounds (EGC) are all connected to the same bus or buses.
Connecting all your Audio Neutrals and Safety Grounds to adjacent or nearby terminals would be good.
Kevin
studio1670
Posts: 6
Joined: Sun Feb 20, 2011 7:41 am
Location: San Jose, CA
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Re: Help needed in finalizing my Star Grounding Plan

Post by studio1670 »

Got it.

Thanks for the response!

Mike
Speedskater
Posts: 171
Joined: Fri Jan 11, 2008 3:21 am
Location: Cleveland, Ohio, USA

Re: Help needed in finalizing my Star Grounding Plan

Post by Speedskater »

Speedskater wrote:
In a main breaker box all the Neutrals and Safety Grounds (EGC) are all connected to the same bus or buses.
Connecting all your Audio Neutrals and Safety Grounds to adjacent or nearby terminals would be good.
After further review, it turns out that not not all main panel boxes are wired the same way. Some don't have a heavy jumper bar or wire between the two terminal strips.

depending on how the neutral bar and ground bar are connected. If the ground bar relies on a screw to the enclosure then the neutrals must not be landed. The neutral cannot use the enclosure as continuity to the neutral bar. 200.2(B) NEC 2008 & 2011)

So in some cases the Safety Grounds will go to one terminal strip and the Neutrals to the other.
Kevin
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