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In Reply to: Electrician Coming Out To Estimate Install of Dedicated Lines posted by "Red" on December 28, 2006 at 11:08:45:
Start your discussion with the electrician at the circuit breaker panel. If it is old, be sure the breakers are still considered safe to use. Our 30-year old house had breakers that were found to not trip if the load increased gradually, so we had the panel replaced when we had to have wires installed for an air conditioner. This is a safety item and you may not like the cost, but it will be cheaper to get all the work done at one time.I would put in more circuits if the panel has capacity for them. All circuits should be fed from the same leg of the 240-volt main, and circuits with particularly noisy items like computers and TV setups should be shifted to the other leg if possible.
I would avoid metal boxes, as the steel has magnetic properties that can affect the sound. Try to get the electrician to route the cables with some separation between them. Bundling them together looks neater, but increases the coupling between them.
Have a separate ground wire run for each circuit. I believe it is permitted to connect these grounds together at the outlets if the different circuits feed a multi-gang box, but you want the ability to separate them. There will be a ground loop if your equipment is grounded. It should be silent, but it will still influence the ultimate resolution of your system, and experimenting with the grounds' local connection might be a good thing to be able to do.
Follow Ups:
I don't know the reason to run separate grounds. If one feeds to both, it seems that you'd have a better ground reference. I don't know. On my new room, I ran 3 dedicated lines and because it was new, I ran all 12-2 romex, so I have separate grounds.But in adding lines, you probably will run conduit and the electrician will run 4 wires for 2 lines, red, green, white and black. In my old house that's what I did and had zero issues and it was my best tweak by far.
I thnk phase is the biggest issue. Yes, keep them off the major appliance legs, which doesn't help for the air or the welder ;)
On digital, I'm still on the fence. Yes, it needs to be off the analog lines, absolutely. But, in my old place I think I had it on a different phase too.
On last thing, do folks know that the neutral also gets connected to the same place as the ground in the panel. Basically, you really have 2 grounds and a hot. It sure surprised me when I hooked up the panel for my media room.
-Rod
I don't know whether separate grounds or a common ground would give better results in all systems; I suspect each case is sufficiently different that it is worth having the ability to try them both ways. One can always tie the grounds together at the audio system if each circuit has its own ground, but if there is only one ground wire installed, it cannot be divided.The outlets are usually so far away from the safety ground-neutral-earth tie point at the panel that the safety ground wire is an antenna for noise. This is why some folks do dangerous things, such as having a separate audio ground rod or lifting the AC safety ground, and get improved sound. A grounded metallic conduit with insulated equipment ground wire that is tied only to the outlet ground sockets provides some measure of shielding for the AC safety ground wire. Perhaps this is what you had in your previous installation.
But in adding lines, you probably will run conduit and the electrician will run 4 wires for 2 lines, red, green, white and black. In my old house that's what I did and had zero issues and it was my best tweak by far.
4 wires, black, red, white, and green. What you have described is 2 separate circuits, a multi conductor branch circuit, not 2 dedicated circuits. Each hot 120V conductor shares the same neutral conductor. Each hot conductor must be connected, one hot to a single pole breaker on L1 the other hot conductor to a breaker on L2. In this case only the unbalanced load of the two 120V separate circuits will return on the common neutral conductor. The balanced load of the two separate circuits are in series with one another. In other words any ac noise from one separate 120V load will flow through the loads on the other separate circuit.
When installing true dedicated circuits,
(1) hot conductor
(1) neutral conductor
(1) equipment grounding conductor.
Each dedicated branch circuit shall have its own equipment grounding conductor as per NEC. If you choose to tie all the equipment grounds together at the load ends of the branch circuits you can do so as per NEC. Some times in the case of long runs of dedicated branch circuits this will help if ground loop problems exist.
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