Instructions to electrician about dedicated line

Bear: While i can understand your thoughts about using one BIG isolation transformer to feed the A/V breaker box for sake of simplicity, what are your thoughts on using multiple smaller ( 15 - 20 amps each ) yet identical transformers wired in parallel ? Sean
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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.