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I need to extend a USB device from a corner of my room to the above the fireplace. Since I'm already going to be installing some HDMI and audio cables through the wall, I'd like to have my USB device run through the same wall plate; I'm not having any luck determining if it's safe to do so, whereas it's quite easy to find in-wall rated HDMI or speaker cables. Would this extender be safe to run through the wall?

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How long is the cable run? –  Craig Apr 20 '12 at 20:13
    
if the wire carries less than 30 Volts and less than 100 Volt-Amperes, you should be fine. –  Tester101 Apr 20 '12 at 20:28
    
These extension cables have active components to regenerate the signal. Would they be allowed in a wall? My gut feeling is no -- but I don't know. –  Craig Apr 20 '12 at 22:38
    
I'm looking at that exact cable. The item i would plug in is only a foot long, and is only going to hold an IR receiver. I am only concerned about it being safe. –  Scott Apr 21 '12 at 13:22

6 Answers 6

up vote 9 down vote accepted

If you are going in-wall over 16 feet, you need an active extender as many have pointed out. One alternative to this is to use a Cat5 extender: this allows you to run Cat5e/6 in-wall (riser or plenum cable is rated for in-wall use), then convert to USB at both ends as needed. One I found at Monoprice is rated for 150ft.

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The downside to these is that you are restricted to USB 1.0/1.1 device speed, but for my needs (a single IR receiver), I'll be fine. –  Scott Apr 24 '12 at 12:59

If you are using USB 2.0 and your run is more than 16 feet, then I would suggest not to run it. USB 2.0 standards specifies that the maximum length to be not more than for 5 meters (16.4 feet). USB 3.0 does not have a length rating but the wire gauge (26 AWG) limits it to 3 meters, or 9.8 feet. Source is from Wikipedia.

EDIT gregmac is bang on with running the cat5. 0A0D is right about the safety end. It's like speaker wire in wall. You can not run just any speaker wire in the wall, it has to be in-wall rated. As for the extenders in the wall, I really don't think any wiring, even low voltage with coupling or connectors that are not accessible should be run in the wall.

The reason I like gregmacs answer is that cat5, with the right connectors can be used for a multitude of things.

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Downvoting as this doesn't address the real question of whether or not it's safe to run in the wall. Will gladly upvote if real question is addressed. –  Scott Apr 23 '12 at 12:43
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@Scott you are correct in downvoting as it really didn't answer. I just took it for granted that you could read my mind. Even tho I was the recipient, I encourage more downvotes as long as the explanation is just and comment explaining why. –  lqlarry Apr 24 '12 at 0:16
    
@lglarry Removed donwvote with edit. The real reason I asked is, there seems to be no real distinction for USB cables for in-wall use (optical cables are another which have no rating, and I'm sure I could find more if I needed to). –  Scott Apr 24 '12 at 12:36

Is it safe to do run USB in the wall? Yes. Does it follow the standard? Possibly. The standard sets the limit at 5 meters, so if it is less than that then you should be good. USB is notoriously testy about current flow. While it may work for your current setup, when you try the new USB 3.0 at high speed you may get some nasty data loss. Not to mention the EMI from the other cables. If you insist on running it through the wall use a high quality cable that is shielded. If you need more technical info the full spec is here Good luck!

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I wouldn't run USB cable in a wall if it is not rated for in-wall installation. You could release toxic smoke or cause a fire if not done correctly.

One option you may not have considered is a Wireless USB hub. It's less intrusive and works well depending on what you are planning to do.

http://www.google.com/products/catalog?hl=en&q=wireless+usb+hub&um=1&ie=UTF-8&tbm=shop&cid=2468399203349082242&sa=X&ei=Yq-VT5mxAYW46QH_tbW7BA&ved=0CLoBEPMCMAE#

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Low voltage wire is not going to *cause a fire. If a fire does occur, however, and the jacket on the cable isn't plenum rated, and the fire reaches the wire, then yes you could release toxic smoke. But then riser-rated Ethernet cable is fine for in-wall installation, but not okay for installation in areas that require plenum-rated cable. That's because plenum-rated wire/cable has insulation that burns slower and releases fewer toxic/acidic gases. I think people are probably getting their terminology a little mixed up, here. –  Craig 11 hours ago

Generally speaking, most low-voltage wires are OK for behind-the-wall wiring.

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Any sources which state this? –  Scott Apr 23 '12 at 12:47

Pretty much any low voltage cable can be installed in a metal raceway (conduit).

You really need to consult your local electrical code if you're worried about this.

But in general, in-wall low voltage cable should be fine if it's rated CL2 or CL3.

Most USB cables you come across are probably UL CM rated (higher rating than CL2/CL3).

CL2X or CL3X (lower rating) with a diameter under 1/4 inch is probably also okay in a single-family dwelling.

The cable ratings indicate how much toxic gas the insulation will emit when it burns, and higher rated cable usually burns more slowly. This is a bigger deal in areas with higher airflow or that move air between different parts of the dwelling (ducts, plenums, vertical penetrations between floors), both because the increased airflow feeds the fire, and because the airflow moves gases to other parts of the building that may not be on fire yet.

Cable with higher ratings can always be substituted for cables with lower ratings.

Cable rated higher than CL2/CL3 include CM, CMP, CMR, CMG, CL2R, CL3R, CL2P, CL3P, PLTC.

Use firestop (caulk or foam) to plug any holes between floors or between rooms.

CL2R and CL3R are riser-rated cables ("R" for riser). They're required for vertical penetration between floors if they aren't in air ducts (which would require plenum-rated cable). Not all inter-floor penetrations necessarily require riser-rated cables in a single-family house.

CL2P and CL3P are plenum rated, which is a higher rating than riser, and are suitable for use in plenum areas/air ducts. Most drop ceilings in commercial buildings act as part of the return air system and require plenum rated cable.

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