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In wall AC cables

Hi to my fellow audiophiles. I am installing an new electrical panel as part of a renovation. As such, I would like to install a few dedicated in wall cable runs to my audio system and welcome your advise regarding best cable to install, brand, gauge, amperage etc. Thanks in advance for sharing your knowledge with me.
audiofool1

Showing 5 responses by cleeds

cleeds
6,070 posts
 
erik_squires
Honestly the normally recommended sizes is best. Having too low an impedance will encourage more noise going back and forth in the wires ... To get uber-fancy run a 220V 60 AMP line and dedicate 220->120 V transformers in the room.
Using "recommended sizes," or using the minimum gauge to meet code, is often not the best approach. By de-rating the wire, you'll reduce or eliminate voltage drop and improve the quality of your ground connection. That can yield greatly improved results. Using minimum wire gauge as a way to reduce noise is introducing a remedy that may be as bad or worse than the disease.

As far as I know, a 220V line is not an option for residential use in the US. Erik may have meant to suggest 240V, but you'll absolutely want to check with local officials before considering that - I think it may be against code in some locations. If you want to install isolation xformers, one option is to keep them out of the room and install them at or near the service panel.
cleeds
6,070 posts
 
erik_squire
There are other safety issues involved with overrating cables in that they may increase the minimum break current of circuit breakers.
It's not "over-rating," it's "de-rating," and perfectly within code. A 20A breaker should trip at the same current regardless of the gauge wire to which it is connected. That's why it's perfectly within code to connect 8 ga or 10 ga wire to a 20A breaker.
Voltage drop should be negligible.
Yes, with de-rated cable, voltage drop should be negligible. What you call "normally recommended sizes" can often result in voltage drop. It's measurable.
I wasn't recommending he use 220 outlets, but that he run 220 service to a transformer ($200 - $500 ish) professionally installed in the room.
Again, I'm pretty sure that isn't always allowed under code, at least in the US.
cleeds
6,070 posts
 
erik_squires


What exactly do you think is not allowed? 220V is an uncommon, but not illegal outlet type.
It’s not the outlet that may not meet code, but your suggestion of a " 220 service to a transformer ($200 - $500 ish) professionally installed in the room." Professional installation here suggests a hardwired xformer - otherwise the user could plug it in himself - and these are governed under code. Always, always, always check local code.
So, increasing the gauge of the cable used at the service entrance may in fact result in having to change the service or main breakers ...
We’re not talking about the cable used at the service entrance, but the gauge of cable used in a branch circuit, and your dubious recommendation to use the minimum gauge cable.

cleeds
6,070 posts
 
lak
10 gauge wire to a 20 amp breaker. Be awear that 10 gauge is a bit harder to attach to the AC outlet, but it can be done for sure.
Yes, the heavier the gauge, the more difficult it is to work with. One workaround when using 10 ga. or 8 ga. wire on a 20A receptacle is to use a pigtail from the wire to the outlet.
cleeds
6,070 posts
 
ozzy

Your workaround would result in the smaller wire being the rated value. So, don't use a pigtail with a smaller gauge to a larger gauge.

Yes, of course, but it's perfectly acceptable to use a pigtail when de-rating wire in the remainder of the circuit, and it doesn't diminish the value of de-rating the remaining wire.
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