dedicated 20amp circuit?

[Herbonbay]

I'm currently removing a living room wall to better accommodate my system. As long as I'm taking out a wall, I've decided to install a dedicated 20amp circuit. I've never been convinced of the need for a line conditioner, never heard a difference, but a dedicated circuit does make sense.

a few questions:

What is the impact of a 20 amp circuit over 15 amp?

Is a 20 amp power cord necessary and if not necessary, is it preferable?

What gauge wire did you use from your electric panel to the outlet?

Did you use an isolated ground outlet?

Regards Herb

[Glen B]

I'm currently removing a living room wall to better accommodate my system. As long as I'm taking out a wall, I've decided to install a dedicated 20amp circuit. I've never been convinced of the need for a line conditioner, never heard a difference, but a dedicated circuit does make sense.

a few questions:

What is the impact of a 20 amp circuit over 15 amp?

Is a 20 amp power cord necessary and if not necessary, is it preferable?

What gauge wire did you use from your electric panel to the outlet?

Did you use an isolated ground outlet?

Regards Herb

What is the impact of a 20 amp circuit over 15 amp?

Greater available power. A 20 amp circuit provides 2,400 watts (20A x 120V) versus the 1,800 watts of a 15 amp circuit. Since you're doing construction you could install two 20 amp circuits instead of one. That way, you will have an extra circuit for future expansion of your system. Just make sure both circuits are on the same 120 volt leg in the electrical panel.

Is a 20 amp power cord necessary and if not necessary, is it preferable?

12 gauge wire is rated for 20 amps. As you may know, audiophile power cords come in different gauges from as small as 16 gauge to as large as 6 gauge. A cord suitable for the rating of the equipment being used is the "correct" one.

What gauge wire did you use from your electric panel to the outlet?

A 20-amp circuit requires a minimum wire size of 12 gauge. The actual wire size used depends on how far the outlet is from the electrical panel and is dictated by the National Electric Code (NEC). If the outlet is far from the panel, a wire size large than 12 gauge may be required. Some folks (myself included) use 10 gauge wire even when the outlet is fairly close to the electrical panel.

Did you use an isolated ground outlet?

An isolated ground outlet is only necessary if an isolated ground circuit is being installed.

[Kevin P]

If you have several high-power amps in your system (e.g. 200 watts x 5 channels or higher), they may require a 20 amp circuit to get enough juice to operate properly. I'd recommend at least 2 20 amp dedicated circuits to allow for expansion. Just make sure the electrician installs all the circuits for the HT on the same side of the breaker panel so the circuits are in phase, to avoid possible hum. I'm going to install three circuits for the HT gear when I rebuild my house, plus a circuit for the projector.

[Herbonbay]

Ok, I'll bite. Would you isolate the ground on this circuit?

Herb

[Kevin P]

You could if you want. Supposedly isolated grounds improve resistance to surges. I don't know if it's a good or bad thing for ground loops. Here's more info on isolated ground circuits.

[Glen B]

If you install romex and a plastic receptacle box (provided the latter is permitted by your local code) you will have an isolated ground of sorts. However, a true isolated ground circuit requires the use of a metal receptacle box and conduit (such as EMT with individual type THHN/THWN conductors or type MC-IG armored cable which has hot/neutral/isolated ground/redundant ground conductors). The redundant ground in the type MC cable is there to reduce the impedance of the spiral armor.

Isolated ground reference http://www.liebert.com/support/white...s/sl_24275.asp

[basementjack]

Isolated ground explanation

Herb -

Do any of your audio components use a 3 prong plug? If so, the I would use the isolated ground outlets.

I've done a lot with this stuff so let me throw in my 2 cents and my 2 cent explanation...

If you're doing the work yourself, don't buy the 35 cent outlets from home depot - instead spend a few bucks and get one of the "commercial grade" outlets - you'll find they have a much firmer grip on the plug. (isolated ground outlets cost about $12 and are already commercial grade. The firmer grip on your plugs can have an impact, especially if you have a lot of bass and the walls vibrate.

In a US 120V 15 amp outlet, there are 3 openings. The wide thin bar is neutral (white wire) the short thin bar is power (black wire) the roundish opening is the ground (green wire)
A 20 amp outlet is the same, except the power opening looks like a sideways "T"

In a normal (non isolated ground) outlet, the ground pin is electrically connected to the tabs that you use to screw the outlet to the wall, and also to the screw that hold the faceplate on. In areas that use metal conduit, these tabs make the connection to ground, and the green wire is not required.

Interestingly, the white wire, and the ground wire, electrically are the same in your circuit breaker panel.

An Isolated ground outlet does not connect the ground connector of the outlet to the installation tabs or the faceplate screw. In this case the ground wire is required. For an audio application, you'd want a single run of green (ie not bare copper) wire to go from the outlet directly to your electric panel. in this way you are "isolating" the ground of that outlet from the rest of the ground connections in your house.

So that's what an isoground does. If you have all equipment with 2 prong plugs, it won't make a bit of difference, except for the firmer grip.

[Herbonbay]

Thank you to all Herb

[Glen B]

For an audio application, you'd want a single run of green (ie not bare copper) wire to go from the outlet directly to your electric panel. in this way you are "isolating" the ground of that outlet from the rest of the ground connections in your house.

The isolated (insulated) ground does not isolate the circuit ground from the rest of the household ground connections, since it terminates at the service panel ground bus with all of the other circuits. The isolated ground provides a grounding path for the connected equipment that is largely free of noisy ground currents only in the circuit in which it is used.

[taz13]

Understand one thing, a residential circut breaker is designed for 80% continuious load. So if you have more then 16 amps of continuious draw a 20 amp breaker is not going to be sufficient.

[basementjack]

I agree with TAZ13, and in line with what Kevin P said, best to dedicate a few circuits if you can, and all from the same feed for US homes with 220 service (I believe UK homes are all single phase service)

To follow up with Glenn B - Glen you're right - any speculation if this makes a difference - I've wondered about this since it's all connected in the box, yet I wondered if the path of last resistance would have the noise go down the grounding rod and not back out the rest of the circuits.

Hey one more crazy thought on AC filtering - has any one ever seen a motor-flywheel-generator type device? Would such a device eliminate all noise on the line?

- Jack

[taz13]

They work by fly wheel effect(read that : very heavy so that any flucuations are smoothed out) and are very noisy but the power out is considered first grade and we use it in our DC converter stations for essential equipment. Also even the small ones are very expensive for any kind of load rating.

[whoaru99]

So, let's make sure I'm straight on this.

1. Dedicated circuits for the HT systems should all come off the same leg of the breaker panel since there can be voltage differences between the two legs. Of course, this is assuming that one is running 120 circuits from a 120/240 panel.

2. If using "Romex" cable and installing isolated ground circuits and outlets, I will need 3-wire w/ground cable.

a. The bare grounding wire will connect to the outlet frame (using plastic/fiberglass boxes).

b. White wire and black wire connect to the outlet as usual.

c. Mark the red wire with green tape at each end and connect to the isolated ground prong screw at the outlet.

d. Black connects as usual to the breaker; the white wire, bare grounding wire, and the red (marked with green tape) isolated ground all connect to the neutral/grounding buss bar at the main panel.

e. The exception to "d" would be if you had a dedicated sub-panel since only in the main panel are neutral and ground bonded together. At subpanels neutral and ground are not bonded, therefore the bare grounding wire and the isolated grounding wire would be connected to the grounding buss bar and the white would be connected to the neutral buss bar.

The caution with isolated ground being that all components in the HT system must be on the same isolated ground circuit or you defeat the purpose and may even be worse off with ground loops, etc.

Do I have it straight?

[Glen B]

So, let's make sure I'm straight on this.

1. Dedicated circuits for the HT systems should all come off the same leg of the breaker panel since there can be voltage differences between the two legs. Of course, this is assuming that one is running 120 circuits from a 120/240 panel.

2. If using "Romex" cable and installing isolated ground circuits and outlets, I will need 3-wire w/ground cable.

a. The bare grounding wire will connect to the outlet frame (using plastic/fiberglass boxes).

b. White wire and black wire connect to the outlet as usual.

c. Mark the red wire with green tape at each end and connect to the isolated ground prong screw at the outlet.

d. Black connects as usual to the breaker; the white wire, bare grounding wire, and the red (marked with green tape) isolated ground all connect to the neutral/grounding buss bar at the main panel.

e. The exception to "d" would be if you had a dedicated sub-panel since only in the main panel are neutral and ground bonded together. At subpanels neutral and ground are not bonded, therefore the bare grounding wire and the isolated grounding wire would be connected to the grounding buss bar and the white would be connected to the neutral buss bar.

The caution with isolated ground being that all components in the HT system must be on the same isolated ground circuit or you defeat the purpose and may even be worse off with ground loops, etc.

Do I have it straight?

In #2 above you said "If using "Romex" cable and installing isolated ground circuits and outlets, I will need 3-wire w/ground cable."

If you are using romex (more appropiately called type NM-B cable/non-metallic sheated cable) the issues that apply to isolated ground circuits are moot, since romex is non-metallic. There is no metal path between the service panel and outlet, other than the ground wire. If you run two grounds with plastic-sheathed cable, all you will have is a redundant ground.

A [true] isolated ground circuit requires the use of metal conduit as I mentioned in my previous post. You cannot use romex and have an isolated ground circuit. What you will have is a standard circuit that happens to be using an isolated ground receptacle. In your case, all you need to ensure is that the ground wire of your romex cable terminates at the ground terminal screw of the receptacle. IMO, the receptacle manufacturers are pushing IG receptacles to the audiophile community without making these facts clear. Those who are unfamiliar with what is entailed, will be misled into thinking that there is some benefit to be gained simply by installing IG receptacles.

A couple of other things. In any application, you cannot re-mark a red wire for use as ground. The only re-marking permitted is of a white wire with black tape when that wire is used in a switch loop (where that conductor is HOT). When it comes to [true] IG circuits, you can have components in the same system on multiple circuits as long as all of the circuits are [true] isolated ground. It is only when you mix IG and non-IG circuits that you will have a problem.

[taz13]

:agree:

[whoaru99]

Boy, it sure is nice to know there are guys like y'all that are willing to try to keep some of us out of trouble!

This attachment is from one of those DIY books you can buy at your local home improvement center. You'd think the publishers would have vested interest to make sure the books are accurate given today's propensity to litigation. There is probably a disclaimer in fine print somewhere...

Thanks for your clarifications!

[brian p]

usually two 20 amp circuits are plenty. you got some good info here from everyone.
keeping both breakers on the same leg keeps the outlets on the same phase so you don't have to deal with opposites. also don't get confused between the difference between grounded and grounding. they only become the same potential at the loadcenter. if you'll notice the grounded (neutral) bar does'nt touch the metal panel, the grounding bar does.
the two are joined (bonded) by a large headed green screw through the neutral bar.
grounded is neutral or white, grounding bonds the non-current carrying parts of a system (metal boxes and such) to ground and is bare or green. 3 conductor w/gr is good for home isolated grounds, but you probably won't need it. you have to have the load center properly set up or it won't even work right. you can write a book on isolated grounds. try it without one. remember also as far as power needs, take your maximun system requirements (power consumption not output) add them up, divide by 120, and you'll
arrive at an amp rating that will guide you on how many breakers you'll need.
good luck.

[Glen B]

you can write a book on isolated grounds.

Actually, there is a book devoted solely to grounding issues. Soares Book on Grounding, published by the International Association of Electrical Inspectors (IAEI) is the bible of grounding systems theory, design and installation.

[Glen B]

Boy, it sure is nice to know there are guys like y'all that are willing to try to keep some of us out of trouble!

This attachment is from one of those DIY books you can buy at your local home improvement center. You'd think the publishers would have vested interest to make sure the books are accurate given today's propensity to litigation. There is probably a disclaimer in fine print somewhere...

Thanks for your clarifications!

The National Electric Code has a provision [219(B)]for re-identification of conductors in a multiconductor cable with tape, shrink tubing or labels but a residence does not meet the conditions for this re-identification. This may only be done in a commerical or industrial environment.