Dedicated Power Lines

I have a 55 year old house with an original 100 amp service which, in a way, worked in my favor because I was forced to upgrade. I did this approx 15 years ago with the addition of a 200 amp box bypassing the old one to serve 220V users such as the clothes dryer, stove and A/C air handler. The 100W box was otherwise left unchanged feeding all other existing circuits in the house. This was a matter of convenience because the 100 amp box is in the garage.

Modifications that were made to serve the sound system were done primarily to protect it, to the extent possible, from potential damage from power feed glitches. I didn't consider it from the standpoint of maximizing sonic quality and it still wouldn't be a priority in my thinking today. Anyway, the modification consisted of a lightning arrestor with surge protection and separate 30 amp breakers from the 200 amp panel serving two outlets on the wall which serves the system. I also use a line conditioner for most of the components in the system. I'm sure that there are some purists that would cringe at all these intervening electronics and several have already reminded me that this protection may provide some peace of mind but is mostly not that effective.

From a purely sonics standpoint, and I'm still not convinced that this is an important issue, I may have gained something by accident. The electrician did use 10 gauge Romex from a roll on his truck and the run of these two wires was relatively short (approx 25ft). They were run in the garage attic, parallel to one another with no crossing of other conductors, and the installation in question was far removed from "noisy" installations such as the central air handler by about 60'.

I don't think I added much to the conversation except to remind those who are doing upgrades to their house power, that it's a good idea and pretty simple, to make accommodations for your sound system at the same time.

I also live in an old house and upgraded my service. I had my service upgraded to a 250 amp service with new breaker box and what I think helped the most is changing to new 0/0 wire from the pole to the new breaker box. The new feed to the house is a much larger wire.

I think if I understand it, if you use both phases of power at home then if you cross the hots you can produce 240volts.
06-21-13:

Coxhaus,

A little background.

Most homes in housing developments in the US are fed from a single phase transformer. The 240V nominal secondary winding has a center tap, CT, midpoint of the winding. The CT is called the neutral.
The secondary winding is called a split phase winding.

The neutral is intentionally connected to earth at the main electrical service of the house. The neutral then becomes the Grounded Conductor.
The other two conductors are called the Ungrounded Conductors. Also referred to as the Hot conductors.

From Hot to Hot conductor there is a difference of potential, voltage, of 240V nominal. From either Hot conductor to the neutral conductor there will be 120V, nominal.
Thus a 120/240Vac grounded 3 wire single phase power system.

Click on single phase power systems.
http://openbookproject.net/electricCircuits/AC/AC_10.html#xtocid174140

I would think anybody who uses 220 power conditioning is subject to this and anybody who uses multiple plugs from different phases are all in the same boat.

If you would take the time and research the archives of audio forums you will find the vast majority of audiophiles when feeding their audio equipment from two or more 120V branch circuits will feed the circuits from branch circuit breakers that are fed from the same Line in the electrical panel, when the equipment is connected together by ICs. All from Line one (L1) or all from Line two (L2) but not from both.

As for your 3 isolation transformers you have the same situation. It doesn't matter whether you fed the xfmrs with 240V or 120V. (240V is best IMO). Two of the 3 will be in phase with one another. The other has a 50/50 chance of being in phase with the other two. My simple test, in one of my previous posts above, will tell you for sure.

IF one of the xfmrs is out of phase with the other two all that needs to be done is to reverse the two primary hot branch circuit wires at the breaker that feeds that xfmr.

Transformer phasing?

Click on phasing.
http://openbookproject.net/electricCircuits/AC/AC_9.html#xtocid174063
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This is a good thread. I got help here a number of years ago when I had dedicated lines installed in my current room. A couple of anecdotal observations, while I am not an electrician and don't pretend such expertise:
1. I thought choosing one leg over another was about finding the side which had less noisy appliances, lighting, etc. connected to it.
2. I agree that we tend to over spec, given the amount of actual current drawn by our gear- thus, having separate dedicated lines to support amps, separate from front end electronics, etc. But, in my experience, using very high efficiency horns, I could hear low level grounding issues that I attributed to the 'difference' in separate lines, i.e., the 'Brits' tend to hook everything up to a single line and then use a distribution box in the room.
3. I like the idea of separating lines for analog and digital but if they are ultimately hooked up to either other through interconnects, i.e, a HT system that connects to the audio system, how much difference does that make? (My HT is entirely separate from the hi-fi and uses a 240 volt step down transformer to isolate it from an analog only hi-fi system).

1. I thought choosing one leg over another was about finding the side which had less noisy appliances, lighting, etc. connected to it.
06-24-13: Whart

There are those that follow that belief. Keep in mind when the house was originally wired 120V branch circuits for the kitchen, laundry, furnace, lighting loads, and whatever other possible loads were somewhat evenly divided, balanced, across L1 and L2 to neutral at the service panel.

In most cases our homes are fed from a utility power transformer with a split phase secondary winding. The way a split phase winding works only the 120V unbalanced load returns on the neutral conductor to the source, the utility transformer.

Example. Say L1 to neutral has total connected load of 20 amps for a given point in time. L2 to neutral has a total connected load of 10 amps at the same given point in time. Only 10 amps will return on the service neutral conductor to the source.
The remaining balanced 10 amps is in series across L1 and L2.

Example. Say both 120V L1 to neutral and L2 to neutral loads are exactly 20 amps each.... 0 amps will return on the service neutral conductor to the source, xfmr.
The two 20 amp 120V loads are in series with one another and are being fed by 240V.

Single phase power systems.

So, so much for trying to feed your audio equipment from one Line or the other because of noisy appliances/equipment.

I do believe it helps not to have dedicated branch circuit breakers that will feed audio equipment installed right next to breakers that feed noisy electrical appliances/equipment. Whether the noisy loads are 120V or 240V. A 240V load example would be the air conditioner condensing unit outside of the home.
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