low voltage and opening back of an electrical box

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  #1  
Old 07-16-11, 04:35 PM
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low voltage and opening back of an electrical box

I bought some Arlington Industries recessed boxes for mounting behind my tv. they put the face of the receptacle back behind the face of the wall so you can get plug in without bending the wire if you have say tv or couch right against wall. so I am going to put two behind tv-one for line voltage and one for low voltage (cable, internet, HDMI, speaker wire, etc). so just noticed that although boxes UL listed for line and low voltage, they only have the 1/2" opening in back with removable plastic NM connectors. That is not big enough for all the wires that may be going into the one box. I know a lot of low voltage boxes do not have a back. can I just cut the back off this one? I know that altering a UL listed device is not allowed. I am not worried about inspection, I am worried about whether there is any danger in doing this. sometimes code has no common sense and just trying to see if this would be the case here-meaning there is no reason that this is dangerous to do and should be allowed but it isn't by code.
 
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Old 07-16-11, 05:31 PM
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Which box did you get? They make a 2 gang that has a divider for the LV. How much cable are you trying to put in the box?

Communications
 
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Old 07-16-11, 05:36 PM
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I'm pretty sure I have seen dual-gang combo boxes at one of the mega-mart homecenters that was a standard line-voltage box with an adjacent low-voltage face frame.
 
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Old 07-16-11, 07:15 PM
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yeh, saw those boxes you are talking about at lowes furd. been a while but there was something I didn't like about it and that is why I looked for something else. I bought the Arlington Industries DVFR1W

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off hand couple things about the box at lowes. it might have built in receptacle that is not tamper resistant? like the clock ones that home depot still sells even though they are code violation where I live?? I wanted one that let you use whatever receptacle you want. also I wanted to separate high and low voltage as much as possible. and 2 boxes made for symmetry-will be visible till I get my TV-this is in niche above fireplace in master bedroom.

don't know how much cable will be putting in, but trying to leave room for expansion. I can see in future possibilities:
HDMI from box to TV, cat 6 to TV?, component video to TV, audio out from TV? till I get working on system not sure what all will need. but I know will need more room than two 1/2" knockouts! don't even think you can get an HDMI connector through that.
 
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Old 07-16-11, 07:32 PM
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I usually recommend as a minimum a double-gang box wherever one thinks they might want a wired telephone, data or television connection and to connect that box to a central hub with flexible plastic conduit. That way they can simply put a blank cover over the empty box and save on cabling costs until they actually need the box.

In your case I would recommend probably a three or four gang plastic box and no less than two 1-inch conduits back to the hub. Since it is all for communication signals I would have no problem cutting out the back of the box or if I could find a suitable low-voltage frame I would use that. The rules for low-voltage communications wiring are much less stringent that for power wiring so I wouldn't worry too much about UL ratings that normally pertain to line-voltage installations.
 
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Old 07-16-11, 11:03 PM
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Will, you could use a LV1N or an LV1 near the box you have or switch to one in my link above.
 
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Old 07-16-11, 11:51 PM
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The video of the product PCBoss linked to. Instructional Videos | Arlington Electrical Products
 
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Old 07-17-11, 03:59 AM
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Since you've already bought the boxes, cut the back off the low voltage box or expand the existing hole. There are no issues with code, and no safety issues with low voltage signal wiring.

Common sense would dictate that you protect the cabling where it enters the box so it doesn't get damaged. (Even plastic boxes can have sharp edges.) Try and keep AC power cables at least 12 inches from your low voltage wiring if run parallel, and cross them at right angles. OK to put the boxes next to each other, but try & run the AC on one stud in the void and the LV cabling on the other.

Your LV cables should be rated for in-wall use.
 
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Old 07-17-11, 07:36 AM
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Use a heatgun to round out the edges on the cut box.
 
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Old 07-17-11, 08:37 AM
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thanks guys. I think I would just cut back off this one, but after answering some of your questions here I realize that furd is probably right and I need bigger box. if one box is dedicated line voltage and other is low voltage, I think probably need a double gang for low voltage. a leviton cover plate has openings for 6 push in units. a component video cable would use 3 and then you have audio as well. doesn't leave much room for HDMI, cat 6, etc. maybe need to switch to LVU2W-double gang low voltage recessed.

Communications


pcboss, the LV1 is not recessed. may not make difference since tv will have to be on articulating arm anyway, but just in case prefer to get recessed boxes. and the link you provided has line and low voltage in same box which I prefer not to do.

I guess could use the one I already have and if need bigger one later just put it in. the way they mount it would be very easy to to this as long as I leave room in the framing to accomadate bigger box if needed. Often times my grand plan doesn't pan out and I may never need all those cable. heck, the wife doesn't even want TV in bedroom!
 
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