Low Voltage

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  #1  
Old 11-07-06, 09:37 PM
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Low Voltage

I will be running telephone, alarm, cat 5, coaxial, and speaker wire as part of my garage project. I have a good bit of experience with 110v and 220v but have never pulled low voltage (LV) and have many questions. Can I pull the cat 5, coaxial and telephone together? How far should the LV be away from 110V/220V wiring? Should the wiring be shielded? Do they make a prefab cable with cat 5, telephone, and coaxial in the same cable? Can standard plastic blue junction boxes be used with the cat 5, telephone, and coax. combination cover plates? How often does this wiring require support? Any additional tips or requirements would be greatly appreciated.
 
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Old 11-08-06, 12:14 AM
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Let's take each question one at a time:

1. Pull wires together? Yes.

2. Distance between HV and LV? It depends on the application as there are exceptions. The best thing to do is read NEC Article 800.133 Installation of Communication Wires, Cables, and Equipment. You can read it here: http://www.nfpa.org/freecodes/free_access_document.asp

3. Shielding? Unless you expect exposure to high levels of EMF or RFI I would not use shielded cables.


4. Prefab cable? I don't know the answer to this one. You'll have to surf around at some cable web sites to find out.

5. Blue boxes? Yes, you can use these types of boxes if you'd like. They also make LV boxes if you prefer. Either type is OK.

6. Support? Again, it depends on the application, but the best rule is common sense. I recommend keeping wires neat, orderly, and out of the way. Communication wires are lighter and more fragile so keep them out of harms way.

Hope this helps!

Rick
 
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Old 11-08-06, 03:20 AM
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Basically, NEC mandates they stay separate (to prevent 120/240 from accidentally energizing the communications tables.), but allows the sheathing of NM cable to suffice for separation. So, you can run communications cables in the same holes and raceways as Romex (NM-B), but not into the same outlet boxes. There are special split boxes and box splitters you can buy that allow you to do this if you want.

No shielding is required, but I wouldn't put speaker wires too close to any electrical cables. Aside from that, rules on routing communications cable- spacing, support, protection, etc, are practically non-existant. You can run them however you feel like. Treating them like you would Romex is safe, though.


FYI, 120V and 240V (and everything 600V and below) are considered "low voltage" by code, so don't be confused if you see that. Medium Voltage and High Voltage are what you find on power lines and some commercial sites.
 
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Old 11-08-06, 04:31 AM
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"LV" wires

Speaker wires ordinarily are not shielded since they are in a relatively low impedance circuit, typically 4, 8, 16 ohms. Hence they are fairly immune to stray pickup.
 
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Old 11-08-06, 05:49 AM
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Excellent. Thank you.
 
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Old 11-08-06, 06:47 PM
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So, you can run communications cables in the same holes and raceways as Romex (NM-B), but not into the same outlet boxes. There are special split boxes and box splitters you can buy that allow you #


Same raceway, only if the insulations are rated the same.

Supports, same as any other cable. 'Neat and workman like".
 
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Old 11-08-06, 07:00 PM
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lectriclee:
Same raceway, only if the insulations are rated the same.
--------------------------------------------------------------
actually, same raceway allowed only if the lowest voltage rated insulation is at least as great as the highest voltage present.

NEC 300.3(C)(1)

I know, I'm being picky. Just wanted to re-phrase what lectriclee posted.
-------------------------------------------------------------------------------------
Do they make a prefab cable with cat 5, telephone, and coaxial in the same cable?


Probably. They make just about any configuration of cable you want if you are willing to hunt for it and pay for it.
 
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Old 11-08-06, 07:30 PM
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Smile

NAG,NAG,NAG. OOOPS, I Meant, NAP,Nap,Nap.
Your correct, It is a Very important point, Thanks.
(I'm a lazy typer.)

RE: Prefab cable. Don't bother, for the 100 or less ft. you need,
You'll have to sell everything. Then you'll have no place to install it.
 
  #9  
Old 11-09-06, 04:23 AM
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Keep your low voltage cables separated from your 120 and 240 volt cables by at least 12 inches. Cross them only when necessary, and only at right angles.
 
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Old 11-09-06, 02:58 PM
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You can get what is called "structred cabling", which is two each of Cat 5e and RG6 in one sheathing, although I don't know if there is any buriable/outdoor grade cable of that sort, if that is what you want.
 
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