Dedicated line which wire?

Thank god it wasn't a grounding question:~)

Sean, thanks for the mini lesson in power cabling. I just bought a new house and plan to have a electrician install dedicated lines. I just surfed the belden site and it's all greek to me. Can you tell me exaxtly what to instruct the electrician to do? Here's what I know. Dedicated ground, 20 amp, star wired, not series. What wire (exactly) should I buy? I also plan to use better ac plugs like PS audio or the FIM. I've heard about whole house surge protection at the panel-what do I need to tell him here? Also, is there different quality in circut breakers too? If so, what's the type/brand to get? Anything else? Thanks in advance...John

I'd like to start by saying I generally agree with what Sean is saying above. I would also like to mention that my profession is Commercial Electrician in Silicon Valley Ca. I have around twenty years experience and have installed many dedicated circuits for all sorts of sensitive equipment.

I'd like to start with a practical look at voltage drop. Why don't we plug in some real numbers that might be used for a stereo or H/T system installation. . What if we say the load is a continuos 15 amps the distance is 150 linear feet from the source (panel) copper wire is being used (k=12.9) Here's how that looks for an electrician trying to size the wire;

VD= 2 x k(resistance x circular mils/1000') x distance x load /(divided by) circular mils

VD= 2 x 12.9 x 150' x 15amps /6530(#12wire) = 8.88 or(7.4%@120volts)
VD= 2 x 12.9 x 150' x 15amps /10380(#10wire)= 5.59 or(4.6%@120volts)
VD= 2 x 12.9 x 150' x 15amps /16510(#8wire) = 3.51 or(2.9%@120volts)
VD= 2 x 12.9 x 150' x 15amps /26240(#6wire) = 2.21 or(1.8%@120volts)

I'd like to note that the allowable voltage drop from the panel to the load is 8% (NEC) So in fact a #12 wire could be used legally in this scenario.

One point I would like to make is the diminishing returns on money invested verses "bang for the buck" Running beldon wire from your panel to your load seems a little extreme to me. (If you do go this route plan on running conduit to protect the wire).
I personally would put the money into isolated grounding or dedicated neutrals.

If you buy wire and twist it together you will need to run conduit to provide protection for that wire. This may be worth the extra expense, as there appears to be some sonic benefits.

MC CABLE has the wire already twisted inside but the ground is twisted in with the hot and neutral. I'm not sure if this would hinder optimum performance? (Comments welcome)

Bumping up the wire size is a good idea. However most electricians are going to think your nuts (Myself included) if you ask them to terminate a #6 wire on a 20 amp receptacle. Especially one that is less than 200' from the panel. #8 would be the most my imagination will allow for a twenty-amp circuit.

THHN is an industry standard and personally it's all I ever use. If you go with romex I think they are making it with THHN insulation around the conductors these days though it use to be TW.

I am of the opinion that it would be better to run two or three dedicated circuits with #10 wire than one with #8 or #6 when you drop the size of the load on the circuit you will reduce the voltage drop. That is to say a 5amp load will have less VD on a #10 wire than a 15-amp load.

As far as breaker selection always match the breaker to the panel manufacturer. I personally like to use the full size breakers when ever possible.

My intention here is not to bash anyone’s comments but instead to lay down some practical wiring methods and common sense approaches. I couldn't agree with Sean more when he said "Weather anyone would want to pay for optimum performance is another story" There is a lot better ways to spend your money in this hobby so lets not be to over zealous on the dedicated circuits.

I hope this helps:~)

A relatively inexpensive alternative would be to run 10 ga. Romex in a 3 wire configuration (~60$ for 250' @Home Depot). Compared to 2 wire Romex, all the conductors in 3 wire are twisted, and contains two hot wires (black and a red), a neutral (white), and a bare ground. Use just the black for hot, white for neutral, and the bare for ground. The red wire isn't attached to anything, and is snipped off at each end. However, one could experiment with grounding the red wire at the panel, or independent ground, and determine if it acts like a shield drain.

Glen, thanks for taking the time to produce the figures and data that you did. It is good to find someone that works in this specific field support some of my basic statements. My line of thinking is that the figures that you provided would probably result in a "best case scenario" and would actually measure slightly worse in a real world installation. Then again, you are the electrician and should know better. I know that many "formulas" put you in the ballpark but you have to finesse the end results from there. Much of my work is DC based and at lower voltage, making line loss even more pronounced.

There is one thing that i would like to point out about your chart though. I have no idea as to what the National standards are, but i know that here in Illinois, a standard 15 amp circuit is run using 14 gauge wire. Glen's chart starts out using 12 gauge, which is standard for a 20 amp circuit. Given the figures quoted, we can see that both gauges of wire are being run "at the ragged edge" of efficiency under those circumstances. If we look at how "in-effecient" 12 gauge is at 15 amps, think about how 14 gauge would work in that situation. This would easily put us at over a 10 percent voltage drop. This is NOT including poor connections or being tiered off of another line.

With the same line of thinking, exponentially calculate the increased losses trying to run 20 amps through 12 gauge. It puts you at about the same 10% power loss ratio. Keep in mind that once you start to heat a wire due to current flow, the wire is no longer operating within its' "window of efficiency" and loss goes up drastically after that point. All of this would meet code in a standard housing development ( at least locally here in Illinois). That is why i stated that "the ratings on wire are a compromise at best".

If you can afford to throw away 10% of the dynamic range or can enjoy your system with 10% compression due to a similar percentage in voltage drop, then stick with what MOST electricians will tell you is "sufficient". Admittedly, this would constitute pulling pretty hard on an individual circuit, but it is not out of the question. People running multiple amps, a large HT system or a LOT of front end equipment might be in this situation and not even know it.

As for me, i like "overkill" and being covered under any situation. Going "overkill" will never leave you guessing as to whether or not it might be "just a bit" better later on. You will never have to second guess yourself and say "maybe i shoulda did XXXXXXX in the first place". Peace of mind in this "over the top" hobby is not easy to come by, so take what you can get when the opportunity presents itself and is under your control.

As to wire suggestions, i'm looking into that. Belden makes a TON of commercial wires. As Glen mentioned, using some of their "fancy" wiring would be WAY overkill in my book. I have used some very simple twisted pair solid conductor wire in the past with great results. I do not know what brand it was, as my Brother used to work at Anixter and would purchase it as we needed it. It was a standard stock item for them though. It is basically standard 2 conductor THHN house wire that the manufacturer twists at the factory, saving you the time and trouble. Believe me, you DO NOT want to try to twist heavy solid conductors for ANY length whatsoever. NOT fun and plenty tough. We then ran a seperate STRAIGHT ground wire ( no braiding, twisting, etc ).

Glen's suggestions are all quite valid, especially those of doing multiple circuits instead of trying to force everything onto one big one. I think that one circuit for the front end components and one for the amp would be excellent and a BIG step up for most people, especially those in older houses. Another way to divide the two circuits would be digital / analogue, etc... If you were running multiple amps i.e. large HT systems, multi-amping, etc, you might want to even consider three or more circuits. They are not THAT costly, especially since you are doing them at one time. Believe me, you'll want to get the most out of your service call. Just ask Glen about Union rates : )

One thing to remember about all of this though: it is VERY important to remember that ALL of these circuits be tied into a common ground. Otherwise, you may end up with an even worse noise floor / hum than you had before. If you want to isolate the "audio ground" from the other ground in the house / building for noise reduction purposes, so be it. Just don't overlook the importance or safety factors involved. Sean
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