Low Voltage Home Pre-Wire Guide:

Wire Types and Sources


In this section:


Cable Ratings

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All the wire that I used was UL rated as either Level 2 or Level 3 (CL2 or CL3). This is a fire rating for the outer insulation jacket of the cable. Though I don't know the numbers, it certifies that the cable insulation will not burn for a certain amount of time at a certain high temperature. Check your local building code for requirements in your area, but Level 2 is accepted in many areas, and Level 3 is good for most all areas in the US. Local building codes will probably require at least some UL level rating. UL rated wire is marked on the wire itself, usually something like "(UL) CL3" for level 3 wire, which is what is marked on the Monster Cable audio wire I used. Twisted pair cables may be marked "(UL) MPR/CMR" or "(UL) CPP OR MPP" or the like, depending on plenum-rated or non-plenum rated cable; see the section on Phone and Data Cable below for details.

Another reason to use wire designed for in-wall use is that it is made for greater noise tolerance due to the usual proximity to electrical wires (AC) in walls. This is done with shielding and/or by twisting pairs of signal wires. I don't know the exact scientific details behind the twisted pair theory, but the idea is that noise induced by half of the twist is "nullified" (in theory) by the other half of the twist. Long runs of signal wires can get noisy if the wires run perfectly parallel to each other.

Also, 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. Perhaps someone else can contribute a better (and more accurate?) description. All I know is that twisted pairs help reduce induced noise, whether it is audio signal cables or data cables. Wire routing is the greatest prevention for AC-induced noise, since crossing the AC line at 90 degrees (right angles) does not produce noise from that line; see the section on wire routing.

Cable jackets may be different materials to meet different UL ratings, but is generally rated for either normal in-wall installation or plenum installation. Commercial buildings usually use plenum-rated wire because at least some of their runs are through air plenums (such as the space above suspended ceilings) associated with heating and cooling systems (HVAC). Building code usually requires plenum-rated wire in such ducts to ensure a fire is less likely to cause burning insulation to contaminate the air system. Plenum rated wire is jacketed in material like teflon instead of the PVC usually used for non-plenum rated wire. Since homes seldom have duct systems where wire is run, PVC is usually acceptable, especially when put in walls. Therefore, all the audio/video cables discussed here are PVC, not plenum rated. Since plenum-rated cable is usually almost twice as expensive as PVC cable (at least in my area), I also used PVC for twisted pair cabling.

Most of the A/V wire we used was Monster Cable®. They manufacture high-quality cable for speaker wiring, signal level wiring, and coaxial cable, all for in-wall installation. Believe it or not, the prices (in bulk, normally 500 or 1000 foot spools) are fairly reasonable. For instance, quad-shielded coax cable from Radio Shack in bulk (1000 foot spool) is about 18 cents per foot; Monster Cable quad coax cost me 24 cents per foot (with large quantity discounts), and the difference in quality is like day and night (see comparison photo). All the Monster Cable is marked every foot with the amount of cable left on the spool. This made it very easy to estimate length of wire runs and remaining wire on the spool. All wire had white jacketing with color-coded stripes for each wire type (red stripe for 16-gauge 4-pair, black stripe for 16-gauge 2-pair, etc.). This made it much easier to quickly tell which wire you are running or had run.


Whole House Audio:

With the above discussion about induced noise in mind, Monster Cable® makes a series of in-wall rated audio cables [called Monster Standard™] that I used for my in-wall speaker cables and audio signal level cables. I used a two-pair (four conductor) cable from my central audio cabinet to each volume control, for right/left speaker pairs. The four wires are twisted together and covered by the UL-approved PVC jacket. This is certainly easier to run than two separate speaker wires! From the volume control, a separate 2-conductor cable was run to each speaker (Monster Cable again, one twisted pair in the same jacket). I used 16 gauge wire for all whole-house audio systems. I know, I know, 16 gauge wire may be considered too small by some factions, but remember, I am not fanatical about audio, this is not for super high-fidelity in each room, and the music is likely to be background music and not ear-blasting. Besides, this is the design used successfully by SoundTrack for many custom homes. Also, Monster Cable claims (I am told) that their 16 gauge wire is comparable to other 14 gauge wire anyway. So, except for the media room and the main speakers in our Great Room, we used 16 gauge wire. Monster Cable also makes 14 gauge and 12 gauge in-wall pairs and quads, though the 12 gauge is several times the cost of 14 gauge.

(photo) Close-up of Speaker Cable Samples

By the way, I know that the subject of speaker cable quality is a hot topic, guaranteed to invoke a lot of lively discussion. Some people think that high-quality cable (like Monster Cable) is a waste of money, and zip cord (ordinary lamp cord) may work as well. However, remember that zip cord does not meet most building code for in-wall installation, and may not last over the years as well as cable designed and manufactured for in-wall use. Look at the photo in the link above, and note the heavy PVC sheath (jacket) around the internal wires, which are themselves separately insulated. This outer sheathing protects the cable during installation and makes the cable last longer. The nylon pull string helps keep the wire from stretching as much while pulling through wall studs. And finally, the twisting of the wires inside the cable sheathing should help reduce noise that could be induced from adjacent electrical wiring, which is more of a problem inside a wall. Regardless of the name brand, cable designed for in-wall use seems worthwhile to me for the extra cost for something as hard to replace as in-wall wiring. Just my opinion...

For signal-level wiring (such as source signals from a CD to the amplifier, source for a sub-woofer, or other RCA-jack terminated signals for pre-amplified source input), Monster Cable makes an Interlink 200-4R-CL Standard Two-Channel Shielded Interconnect Cable. This is about a 20-gauge wire pair cable, substantially heavier than any normal pre-made RCA-jack type signal cable. Actually, this cable is two pairs (4 conductor) for right/left channel, and each pair is shielded separately then jacketed. Both pairs are then covered by an outer UL-approved PVC jacket for in-wall installation. If the 20-gauge nature of this wire seems small, try dissecting a standard patch cable normally provided with a CD player or similar equipment for connection to the amplifier -- talk about hair-thin wires!

(photo) Close-up of Signal-Level Cable


Media Room Audio:

Since most critical listening and higher volumes are used in the media room, SoundTrack designed in larger gauge speaker wires for the main speakers - 14 gauge wire pairs. However, due to a shortage of this Monster Cable size at the time, SoundTrack substituted 4-conductor cable instead of 2-wire for the same price. This actually provided a benefit beyond what I had planned, since it allowed doubling up the wires for the main speakers; I will just use two conductors for each speaker pole connection instead of one, making the effective gauge of the wire considerably more than even a single 12-gauge wire! Considering the cost of 12-gauge wire, this provided a super main speaker wire relatively inexpensively. As a bonus (and something worth considering for your own system, regardless of the wire gauge used), the four wire cable could be used to drive bi-wired speakers, where one amplifier output is used to drive just bass frequencies (one speaker pair) and another is used to drive high frequencies (the other speaker pair). Some speakers are made this way since such a large percentage of the amplifier's power is needed for bass. With the separation of the power going to the bi-wired speaker, the 14 gauge wires (separated) should be more than adequate to drive the speakers cleanly at high power. Thus, a four-conductor cable for each speaker would make a very versatile installation for either standard or bi-wired speakers, providing future expansion of your system. To continue this concept, four-conductor 16 gauge wire was used for the seven (front pair, rear pair, side pair, and single center channel) surround speakers in the media room instead of the two-conductor 16 gauge wire recommended by SoundTrack. The SoundTrack consultant informed me that Monster Cable's 16 gauge wire is the only 16 gauge wire approved for THX certified sound systems (normally, 14 gauge wire for surround speakers is required for THX certification).


Video Coaxial Cable:

CEBus recommends the use of RG-6 coaxial cable for the two pairs run to each TV location. RG-6 uses a larger gauge center conductor (18 gauge) and has a foil shield in addition to the braided shield compared to RG-59. RG-59 is the standard coax cable used for cable TV installations and the like, until recently. RG-6 has a lower loss at higher frequencies than RG-59. However, I have found that there are different grades of RG-6 cable, depending on manufacturer and cable specifications. Most consultants and sources recommended quad shielded cable, which is made of a foil shield covered by a braided shield covered by a second foil shield covered by a second braided shield. In addition, the braided shield may consist of different coverage, measured in percentage of coverage. For example, a 30% braid is a much looser braid made of fewer strands of copper or aluminum than a 60% braid. A 60% braid is very tightly woven. Finally, the center conductor may be made of solid copper or copper-covered steel. The copper-covered steel is used to provide greater rigidity when the center conductor is inserted and re-inserted into a coax jack, since the F-connectors used for coax termination use the center conductor as the "pin" for the connection (others have disagreed with me on this). However, I feel more comfortable with solid copper conductor (copper is a better conductor, does not get worn off with multiple insertions, and is not as subject to manufacturing quality control during the copper plating operation) -- my opinion only. Monster Cable makes the best quad-shielded RG-6 coax cable I have seen. It uses a 60% (or higher, it appears) all-copper braid for both braid shields, has a solid copper center conductor, and is quite flexible and tough.

(photo) Coax Cable Comparison

Two runs of coax were made from Node 0 to each TV location. To make it easier to distinguish between the two coax wires, several sources recommended using either different colors for the two coax wires, or using different manufacturers. Since Monster Cable only uses white coax, I chose to use a different manufacturer for the second coax wire. I still used quad shielded RG-6 coax, and the wire (also purchased from SoundTrack) was supposed to be of quality similar to Monster Cable coax, but was a little cheaper (2 cents per foot less than Monster). However, after I installed most of the wire, I stripped an end to look at it and was disappointed. Where the Monster coax was tightly braided with copper (about 60% coverage braid), the other coax was loosely braided (about 30% coverage braid) with aluminum alloy wire strands. If I had it to do over again, I would probably stick with the Monster coax for the small difference in price, and just carefully mark both ends of the second wire for identification.


Phone and Data Cable:

Phone and data (LAN connections, infra-red audio control data, etc.) wire is normally 24 gauge (AWG) twisted pair cables with four pairs of wires (8 conductor). Solid conductor wire is used to allow connecting to 66 or 110 punch-down blocks at the central node, for easy and versatile interconnection. CEBus specifies 24 gauge 4-pair for both phone and TPBus. I could not find much more than this for TP wire specifications in the CEBus book, so I discussed LAN and related cable requirements with several sources who had experience in LAN and phone installations (IS department technical people and installers, wire distributors, etc.).

In addition to the UL level rating for wire (level 2 and 3 fire rating required for in-wall installation), twisted pair cabling is rated by a "category" specifying essentially the number of twists each pair has per unit of length. I never really found the specifications for the actual count of twists per foot for each category, but it really boiled down to the most common types of wire being category 3 and category 5 TP cables. Cat 3 cable is commonly used for 10BaseT wiring, which is 10 Megabit per second LAN specifications often used for Ethernet networks. Cat 5 cable is much more tightly twisted, and can support up to 100 Megabit networks (Token Ring, Asynchronous Transfer Mode, etc.). Most companies are moving toward installing cat 5 wiring to plan for such 100 Mbit systems; if it is good enough for 100 Mbit systems, it is good enough for me! Cat 3 wire is usually better than what phone companies install in houses for phone wire (phone cables don't really need much twist), so I used it for phones. So why did I install both? Well, though this is relatively cheap wire, cat 5 wire is still about twice as expensive as cat 3; I wanted two separate cables to avoid cross-talk; and the cat 3 cable I got was tan colored while the cat 5 cable was purple, so it was easy to distinguish during installation and maintenance. Of course, this was only valid since I needed multiple 1000' spools of cable; if you only need one spool, it may be more economical to just get one spool of cat 5 cable. I did not use shielded cable since everyone I talked to thought unshielded was fine as long as I was using cat 3 or cat 5 (shielded cable is much more expensive). BTW, yes, there is a category 4 cable, but it is not used much due to the more common use of category 5 for high-speed LANs.

(photo) Comparison of Cat. 3 and Cat. 5 Twisted Pair

The category rating is usually printed on the TP cable jacket, and usually spelled out like CATEGORY 5 or CAT. 3. You can easily see the difference between cat 3 and 5 by removing a few inches of the outer jacket to see the twisted pair wires inside. Cat 3 wire does not have very well distinguished twists to the pairs (blue and white/blue are a pair, green and white/green a pair, etc.) unless you strip about a foot or so of the jacket. Cat 5 wires are very tightly twisted (a couple of full twists per inch) and the pairs can be easily distinguished and separated as pairs.

In addition to the category printed on the cable jacket, the fire rating with codes like MPP (MultiPurpose Plenum), CMP (CoMmunications Plenum), CMR (CoMunications Riser), MPG (MultiPurpose General purpose), etc. This is

usually not critical, unless you need plenum rated cable (in which case you should look for codes like CPP/MPP) -- just ask for category 3 or category 5 four-pair 24 AWG wire that is UL level 2 or 3 rated, depending on code in your area.


Wire Type/Cost Chart:

The following chart illustrates the wire types I installed, the lengths I used, and my cost per foot. Wire types with an asterisk (*) indicate Monster Cable brand. Note that the Monster Cable prices reflect a volume discount; full retail prices seemed to be about twice the amounts shown below. Also, the price I paid for the S14-4 wire was the price that would normally have been for S14-2, but SoundTrack was out of stock on the 2-conductor wire and just substituted the 4-conductor wire at the same price. The descriptions at the top of the chart indicate how the wire was used.

Wire Types:

Wire Type | Cost/ft. | Total Length
----------+----------+-------------
16g-4*    | $  .49   | 2000'
16g-2*    | $  .32   | 1500'
14g-4*    | $  .44   |  400'
IL200*    | $  .54   |  800'
RG-6*     | $  .24   | 2000'
RG-6      | $  .22   | 1000'
22g-4     | $  .08   | 1200'
22g-8     | $  .16   | 2000'
24g-8:3   | $  .044  | 3000'
24g-8:5   | $  .095  | 2000'

Purchase Sources:

I purchased most of the audio and coax wire from SoundTrack because they would sell it in any length, I could return any length that I did not use (not just in multiples of 500 or 1000 feet), and their prices were very comparable to mail-order with the volume I purchased. I did purchase a spool of Monster cable (4-conductor 16 gauge) from Home Automation Systems, Inc. (HAS, mail order), but the savings were not really enough to justify the gamble that I might be stuck with too much wire I could not return for credit, so I was conservative in purchasing mail-order. Also, I goofed and did not read the fine print on another two-conductor spool I purchased from HAS; it was not rated for in-wall installation. They gracefully credited me for the return of the roll, though.

I purchased the telephone and LAN cable (both category 3 and 5 four-pair twisted pair) from a wire warehouse called Allwire, Inc. in Denver (303-295-0106). Their prices were quite a bit lower than other local houses, often by 50% or more; so shop around for prices. They sold both 500 foot and 1000 foot spools or dispenser packs, and always had it on hand.

I had a hard time finding 22 gauge wire. None of the wire houses stock it normally; they consider 22 gauge telephone-type wire a "dinosaur", saying it has been replaced by 24 gauge. For the 22 gauge wire I needed (as recommended by SoundTrack for keypad/infra-red wiring), SoundTrack sold me what I needed. However, it was considerably more expensive (about three times the cost of comparably rated 24 gauge). Even SoundTrack had trouble getting me more than my original order -- it was delayed by over a week.

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