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Jim Leach 3rd April 2010 06:31 PM

"Ideal" power line from Service Panel
Hello everyone.

Since I'm doing construction (remodeling) I thought this was a good place to ask this question. (that, and I couldn't find a better place!)

So, what I'm doing is reconfiguring 1/3 of my first floor to be a 'media room' which is the TV room and Stereo room (and a small office in the corner and the [upright] piano will be in here as well).

Since it is the first floor, I have full access from below to run dedicated power just for the stereo system, totally isolated from all the other electronic paraphernalia in the home.

So, here's my plan:

Dedicated 20 amp breaker in the panel (which was just fully replaced/upgraded to 200-amp service; full copper throughout and new 6 foot ground rod), across the cellar ceiling to a 20-amp floating ground outlet "Hospital outlet".

Along the way, I was thinking it might not be a bad idea to run the Romex inside a piece of copper pipe (earthed). Steel pipe is out, as it will probably become magnetized. (Correct me if I'm wrong, but this will be close to 50' run)

I also have a (HUGE) 1:1 isolation transformer/conditioner from an old computer mainframe. 20 amp input, 19.5 amp output. Perfect. The plan was/is to run into this (mounted on the wall in the basement) and out to the outlet upstairs- a very short run <6 feet.

Since the original concept, I have thought about some improvements to the design:
  • Use stranded 12-ga cable for the A/C feed, as a twisted pair in the copper pipe (as opposed to solid 12-ga Romex), with the ground running parallel (or possibly counter-wound on the outside of the twisted pair?) inside the pipe.
  • Split the A/C at the isolation transformer so only the analogue components use the "filtered" power; with all the digital components using the 'unfiltered' by-pass A/C line (this would include the DVD player[s] and other digital equipment as well as D/A converter[s] and CD transport[s]) To hopefully isolate the 'digital noise' from the analogue A/C line.
So, I guess the question is: if you had this (somewhat) unique opportunity, what would you do?

Speedskater 3rd April 2010 08:03 PM

Fro everything you need to know see:
Jim Brown, AES Committee Chair has an excellent paper on power and grounding.
This paper now has been updated and has an International Wiring Version.

See Jim Brown, Audio Systems Group:

The rest of his some 50 plus papers at:
Audio Systems Group, Inc. Publications

If that's not enough see:
The Bill Whitlock of Jensen Transformers Seminar paper

The Jim Brown of Audio Systems Group white paper
"Power and Grounding for Audio and Audio/Video Systems"

"The TRUTH" from ExactPower of Middle Atlantic Products
ExactPower(tm) - Home of the Residential Power Integrity System

or a different version of the same paper

"Power White Paper" from Middle
Middle Atlantic Products - White Paper - Integrating Electronic Equipment and Power into Rack Enclosures

Speedskater 3rd April 2010 08:10 PM

Along the way, I was thinking it might not be a bad idea to run the Romex inside a piece of copper pipe (earthed). Steel pipe is out, as it will probably become magnetized. (Correct me if I'm wrong, but this will be close to 50' run)

No advantage between copper and plastic!
It's the soft steel that does the job.
It wont get magnetized with all that AC current de-magnetizing 60 times a second.

I would rather have all the audio equipment on the same circuit.

All the ground rods (6 ft. is short) must connect together at only one place!
That place is very near the main breaker panel.

gootee 3rd April 2010 08:16 PM

I don't know if any of it it could make much difference. But I might at least consider running several separate power/ground runs to several separate outlets, and maybe even a ground-only run or two, to dedicated ground terminals (for what, I don't really know).

Mainly, just make sure you install about twice as many outlets as you think you might need. And while you've got easy access to the walls, etc, you might also want to install proper wall-plate hookups for whatever else might eventually be desirable, such as audio, data, antennas, etc.

You might even want to consider a separate whole run from the pole transformer to a separate box, first. But, as I implied, considering all of the miles of junk between you and the source of the power, I don't know if any of it makes sense.

I guess you could also consider some sort of centralized power conditioning or filtering, too.

I would probably use some really-thick stranded wire/cable, for everything, maybe especially the grounds. Maybe some of the stuff they use to connect automotive starter motors would be good.

Speedskater 3rd April 2010 08:55 PM

The ExactPower & Middle Atlantic Products papers have good sections on using isolation transformers. (the 2 papers share some common pages, but each has additional stuff)
This is also a good page: - Power Distribution

No difference between solid and stranded wire except for ease of installation.

Twisted pair (really trio) is a good way to run power wires (even Romex).

The power company won't like the idea of running another service entrance.

I like to keep the length of AC wires between components as short as is reasonable.

Speedskater 3rd April 2010 11:36 PM

On second thought a copper tube would be better than a plastic tube.
But nowhere as good as an EMT conduit.
Which is not as good as a heavy steel conduit or pipe.

Don't mount a big power transformer anywhere near your equipment.

prairiemystic 4th April 2010 05:31 AM

I did a recording studio and the biggest change was breaking the neutral-ground tie using an isolation transformer with subpanel and dedicated ground rods. So much noise gets in there, as neutral is wired all the way back to the substation and then it gets tied to ground in your service.
I put an array of ground rods in, verified their impedance (as they better handle 20amp faults too!).

SoNic_real_one 4th April 2010 07:09 AM

Isolation transformer does ZERO for filtering the noise in the line. The noise is mainly HF noise and that passes from primary to secondary wound by inter-wound capacity. You would need transformers with a foil of grounded copper shield between the primary and secondary to cut that capacity - usually the industrial isolation transformers don't have that.

Forget about Romax or EMT conduit. Buy some AC cable with isolated ground (IG). Or MC cable with normal ground and isolated ground. Those cables have copper conductors, twisted arround each other. Do NOT use stranded conductors - they require special termination in order to maintain good contact over years.
Installation must have isolated ground receptacles but it MUST be done corectly, as described here:

An isolated ground receptacle (IGR) can reduce electrical noise, but if installed incorrectly, it can create a dangerous installation. This receptacle differs in construction from its self-grounding counterpart. The grounding terminal for an IGR is insulated from its metal mounting yoke. This means you must connect the grounding terminal directly to an effective fault current path by an insulated equipment grounding conductor. To ensure the device you're installing is an IGR, look for the Code-required orange triangle located on the face of the receptacle.
I would go with #10AWG conductors (even if NEC allows for #12AWG) on a 20A breaker. Voltage drop (dependent of load) will be greatly minimized.
Also, any kind of "conditioners" will increase the (variable) voltage drop and they are not good for audio. Regardless what salesman say. The only thing that can be on the line is some kind of surge arrester device.

Also, in the audio center, bring two or three dedicated circuits - not sharing the neutrals and all from the same phase (breakers from the same side of the panel). Balance the panel load with consumers somwhere else in the house. Using the same phase will minimize the interferences.

You don't need other ground rods beside the one at the service entry - it is banned by the NEC (interfere with GFI receptacles functionality) and will create ground loops that could pick up hum. Neutral and ground shall be tied toghether just at the main panel.

Jim Leach 4th April 2010 12:46 PM

See! I knew this was the best place to ask this question!:D

Just to clarify a few things:

The ground rod I was referring to is the new one installed outside where the service enters the house. I will NOT be adding a second one. It may be 10' long (probably is if that is code requirement) as I did not see it before it was pounded in...

Isolated ground outlets will have an isolated ground; boxes are plastic.

Good call on keeping phase the same! That was something I did not consider.

Terminating the ends of the (stranded) wire won't be a problem, if that is the best way to go up to and excluding the terminations. I can work with the wire; I just need to know it is the better choice in wire for the run. If not, solid is easier to deal with for sure. If I do go solid, should I pull apart the standard Romex and strand that? I can't imagine parallel solid is the best way to go for interference rejection... (but I'm not sure, so I'm asking!)

It seems like the steel conduit is the way to go up to the transformer. On that note, this thing is a line filtering transformer for a main frame- NOT an off the shelf 1:1 transformer. It was made to 'clean up' the power for an old-*** computer. I've had it for a while. It has its own gravitational field. I think it's made of depleted Uranium. It's a bit heavy- I may need to pour a slab for it... It does make a bit of noise, so it will be below the floor of the listening room, and only the output will come up to the room.

What about the analogue/digital separate outlets? any worthwhile advantage, or should I just have a secondary line conditioner on the outlet (one for Analogue and one for digital) to provide isolation?

Zero Cool 4th April 2010 02:11 PM

One thing i will caution is that NONE of this will pass electrical inspection if not followed to code carefully. and trying to get your local inspector to understand what your doing and why is a whole other issue. I have dealt with this in several new construction recording studios and large home theaters. Electrical inspectors don't necessarily understand star grounding, low impedance ac runs. they think its all the same. and trying to get the inspector to understand a balanced power system whooooo! yeah that was fun. it was clear to everyone including him that i knew more then he did and he got mad and pulled the electrical permit on us. we had to fight to get it back and show proof that what we were doing was safe and by the book. In the end he relented and signed it but not because he ever understood it or wanted to.

SOOOO, things like stranded wire, copper pipe etc are not going to fly past an inspector. I would suggest you speak with your local and make sure of what you are doing before you do it!

Once you get cleared...I would mount the isolation transformer as near the room as possible to keep the secondary feed as short as possible. I would also think about HOW you are going to mount the transformer to reduce hum/buzz from being transmitted into the structure. Mounting on rubber pads or isolators is recommended. and use flexible plastic conduit as well.

and in the end you haven't done anything to reduce noise or stabilize voltage so i wouldn't go too overboard here.

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