Soundscape Articles of Interest - Wiring Guide

Wire Routing and Installation

Running Wire

AC current in 120 (or 220) volt lines produces a magnetic field in wires running parallel to the AC current. This produces hum on audio wires or noise on data wires. Twisted wire pairs help reduce this noise, but can't eliminate it. Careful wire routing is the is the best way to prevent AC-induced noise. Building codes usually require plenum-rated wire in certain areas such heating ducts to reduce the risk of fire. Plenum-rated wire's insulation is less likely to burn and contaminate the air system.

Routing Around Electrical

The main thing to watch in routing low-voltage signal cable is avoiding high-voltage AC wiring. It is OK to cross low voltage signal and speaker wires at 90 degrees to electrical wiring (cross perpendicularly). Avoid running parallel and close to electrical wiring. This may cause noise in speakers and could cause data errors in data lines.

You should never run the cable in the same holes as AC for parallel runs&emdash;keep at least some separation, and keep parallel runs very short. Low voltage wiring should also never go into the same wall box as AC. Running a thousand feet or more of cabling can prove to be quite a challenge! The keyword here is "planning." Foresight and organization will pay off in the long run.

Planning Routes and Pulling Cable

Spend time finding routes for runs and individual locations prior to drilling holes and pulling cable. Plan main cable runs along the full length of the house from which you can split out individual runs. Make sure these main runs are well away from AC runs (electricians will be putting in such main runs, too) due to the length and number of signals that would be affected by noise. Ensure that such main runs (or any smaller runs) do not get blocked by a lam beam or steel beam, and that they can hold all the wire. A good, easy location is across the lower member of roof trusses. You can tape together several wires going along the run. When pulling through trusses, do not pull the cables through the center of a "V" section&emdash;the wire will settle in the bottom of the "V," and settling of the house or expansion/contraction may pinch the cables, possibly causing shorts or cuts years down the road. When pulling the cable, either through holes in studs or across trusses, pull slowly. Don't yank or pull the cable too tight, especially around corners or areas that might get pinched or kinked&emdash;it's not worth breaking a wire, which may not be found until it is way too late.

Remember to clearly mark any cable runs. If you have several people helping you run cables, organization during the cable pulling is even more important. You can often end up with a couple of people scratching heads and planning a route around AC cables, lam beams, and congested locations, while everyone else is waiting to drill holes and run wire. Plan the main routes and many of the individual routes in advance; paint or mark the paths on the joists and ensure you don't get trapped by impassable lam beams 3/4 of the way to the destination. A two-man crew is ideal for wire-pulling. After running the wires, staple them to the studs to avoid getting a wire pinched between the drywall and the stud. For bundles of cables, use those plastic insulated staples (hammer needed) used for AC electrical wire. you can also use metal electrical wire staples, but don't drive them deep enough to pinch the cable. Keep the cables in the middle of the stud to avoid an angled drywall screw or one that just misses the stud. Staple cables close to outlet boxes to also reduce the possibility of lost cables. Drywall installers will push the wires out the back of the box to get them out of their way.

· Stuff all cable ends completely into the boxes to avoid damage during drywall. If

· you need to run cable near the surface of a beam, be sure to use a steal nail plate on the beam over the wire path. This will prevent a drywaller from nailing into your cable and shorting out a wire, a very costly error, if you discover it after the house is textured and painted.

If you use surface-mount speakers, drive a nail into a stud at the location you will terminate the wire and tape the wire to the nail so it sticks out into the room. Dry wall installers are notorious for hiding anything they can behind the dry wall. The nail with the wire is a more sure indication that the wire must be brought through the wall. Don't rely on a walk-through with the planner&emdash;it's the guy driving the nails you must guide. If you use recessed wall speakers, locate the wire where you want it, coil it, and photograph and document its . Iocation. Putting speakers on outside walls may not be a good idea, but if you do it, make sure you pull the wire through the insulation after the insulators hide it from you. I recommend getting the drywall up, or even finished, before cutting the hole for in-wall speakers so you can carefully fine-. tune where you want the speaker on finished surfaces instead of a visually different set of studs. You could also install ; a "hole guide" before the drywall goes up so that the drywall installers will cut and finish the hole for you.

With everything clearly marked and documented on the architectural plans, choosing the electronics and final t installation is all that is remaining. I recommend consulting an experienced. - licensed and insured custom retailer/ installer to help with the selection of what will ultimately be installed as a system. There are also numerous Home Theater publications that regularly make recommendations of components. Consulting these may be extremely helpful if you are to be involved with final equipment selection. One final caveat. be sure to ask for and verify references, from any installation company you consider. The results of a good installation will reflect well on you, but poorly designed and installed systems can cause you seemingly unending aggravation.

Marc Silver is the owner of Soundscape in Santa Rosa, CA. and an expert with 28 years of comprehensive experience in audio and video.

EXTENDED WARRANTY INFORMATION

Updated: January 1, 2001

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