Instructions to electrician about dedicated line

Sure, Sean, that's pretty good in principle - but you have to think about what happens to the grounds too...

Also, are you saying multiple 240vac lines, or 120vac lines?
One of the advantages of the 240-->120 stepdown is that it makes for a way stiffer line in general.

I'd be worried about voltage drops over multiple lines being different, and causing a ground problem on a 120v-->120v iso set up. With 240vac you have two hots and a dedicated ground there... dunno, I haven't thought this through all the way...

I'll have to get back to you later tonight. Running late today : ( Sean
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Bear, the system that i was thinking of would make use of multiple high current isolation transformers all wired in parallel. These would be used for one 120 volt feed into a secondary breaker box. This box would be used strictly for A/V gear and would have a dedicated ground.

To achieve this, you would have a parallel feed coming from the mains of the houses' primary breaker box feeding the isolation transformers. In order to protect the transformers should a winding(s) short out, fuses would be installed on both the hot and neutral legs between the transformers and the mains. The parallel wired transformers would then feed the input of the A/V breaker box.

In effect, every circuit connected to this box would be filtered and isolated from the rest of the house and whatever noise was coming in via the outside lines. Not only would you have dedicated lines, those lines would all be filtered. One could then use smaller isolation transformers at the component feedpoint as needed. My primary thoughts are that one would want to use such an approach for digital gear. While this is not so much to further filter what is going into the digital components ( although it would do that), i was thinking more along the lines of keeping the hash and trash that such gear generates from being pumped back into the line and other components.

The total output of the parallel wired transformers would be rated for a higher level than what the secondary breaker box was rated for. This would insure that the transformers could not be damaged due to pulling on them too hard. If such a situation started to develop, the main breaker on the A/V box would trip long before the transformers could come close to saturation. At the same time, running more isolation transformers than needed would also guarantee a measurable amount of headroom so that core saturation would never take place. This would keep the power cleaner with less distortion than what other current limited filters might introduce.

Does this sound like a plan ? Any thoughts / suggestions ? Keep in mind that i've partially based this on the fact that i already have several "beefy" identical isolation transformers. I have not ruled out going to one "huge" transformer as that would surely be far simpler to install. At this point in time though, i've not run across anything that was reasonably priced although i have been looking. Sean
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Sean,

My comments were strictly regarding CODE requirements. The NEC only considers heat generation withing a cable when specifying its ampacity (current carrying ability). Many electrical engineers make their living sizing cable to carry power to voltage sensitive equipment.

I like your idea of isolation transformers on your system's dedicated lines. It would be easy for me to incorporate that addition to my system. One question, though: if cleaning up power is as easy as installing a transformer, then why are the PS Audio Power Plants so popular? It would be interesting to try a Power Plant in the same system using an isolation transformer and not using an isolation transformer. Then you'd know how much regenerating the AC sine wave contributes to the effect of the PP.

I'm not claiming that isolation transformers are better or equivalent to power regeneration. There is NO substitute for power regeneration. Regenerators start from scratch and provide the best that they can give you whereas isolation transformers are simply trying to separate the good from most of the bad. With isolation transformers, you can still end up with a high level of distortion if the sine wave is not "clean" to begin with. TRUE "power regeneration" corrects this problem but is EXTREMELY inefficient ( high levels of thermal losses / heat build-up ). This is not to say that i think that the PS is the best that one can do in terms of having "clean AC", but it is probably the most commonly used amongst audiophiles.

Having said all of that, i do think that isolation transformers have their place. So long as you never come close to saturating the transformer, i think that they are less detrimental to AC than most PLC's and many times, do a better job of getting rid of noise. There are a few "good" PLC's that simply make use of multiple smaller isolation transformers with additional circuitry supplementing the job that the transformer is already doing. Obviously, a smaller transformer is suitable for line level components and / or sources, but you would not want to run a power amp through one. Personally, i would not want to run a power amp through a smaller PS Power Plant either. If you had a very small amp or one that ran in Class B or was a "switcher" and had high efficiency speakers, i would not see a problem with doing so. Since most all of my speakers are low impedance and low efficiency and most of my amps are relatively inefficient high bias designs, that would not work for me.

If i had my "druther's", i'd "druther" have my own high current AC generator ( with a BIG muffler ) and a "kick ass" voltage regulator in the backyard OR be able to run off of a bank of batteries. Neither is practical for me though, although the generator might be more feasible depending on where i relocate to. I will probably leave an option in the wiring to either draw off of the AC line or be able to insert a generator into the path if / when i move.

Right now, i have enough transformer ( 170+ lbs worth ) to isolate at least 60 amps of current at 100% duty cycle and up to 80 amps for an extended period of time. I'm working on doubling that capacity. I'd like to have all of the "goodies" that i need to do this before i relocate. That way i can get everything wired in / laid out prior to moving in all of my "junk".

As i mentioned, this will feed a breaker box that will feed MULTIPLE systems, not just one. That is why i want such a high current capacity. While i will never have all of the systems "cranking" at one time or be able to pull that type of power at once, i am a firm believer in designing for "worst case scenario". My motto has always been "over-kill baby, over-kill". I'd rather "feast all the time" rather than "famine" just once : ) Sean
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