CL2 through same hole as NMB?

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tallgirl

tallgirl

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Controls Systems firmware engineer
I went to pass a piece of CL2 wire (door bell) through the same ceiling plate hole as two pieces of NMB and was told not to. CL2 has at least 150v insulation and the NMB will (obviously, since it's a house ...) be carrying 120v.

What did I do wrong? I thought that as long as the insulation was sufficient for the voltages I could mix and match wires through the same hole.
 
You can put the doorbell wire through a bored hole that contains NM cables. I try and separate low volt from high but it is not necessary. The jackets on the cable are separating the wires. That's my understanding.
 
Dennis, that was my understanding as well, based on 300.3 (C) (1). I know a hole drilled through a 2x4 isn't the same as an enclosure, cable or raceway, but if it's permitted in the same raceway, I don't see how it's not permitted in a hole ...
 
tallgirl said:
I went to pass a piece of CL2 wire (door bell) through the same ceiling plate hole as two pieces of NMB and was told not to. CL2 has at least 150v insulation and the NMB will (obviously, since it's a house ...) be carrying 120v.

What did I do wrong? I thought that as long as the insulation was sufficient for the voltages I could mix and match wires through the same hole.
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Sorry to be a party pooper, but 725.55(J) say its a no no. (2" separation required)

Edited after re-reading 725.55(J) again. I may have mis-spoke. May have to think about this again.
 
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rlMutch said:
Sorry to be a party pooper, but 725.55(J) say its a no no. (2" separation required)
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That rule is for conductors, not cables. No separation is required.

I frequently run doorbell and t-stat circuits in the same holes as NM cable.
 
Rod, keep reading???

(J) Other Applications For other applications, conductors of Class 2 and Class 3 circuits shall be separated by at least 50 mm (2 in.) from conductors of any electric light, power, Class 1 non?power-limited fire alarm or medium power network-powered broadband communications circuits unless one of the following conditions is met:
(1) Either (a) all of the electric light, power, Class 1, non?power-limited fire alarm and medium power network-powered broadband communications circuit conductors or (b) all of the Class 2 and Class 3 circuit conductors are in a raceway or in metal-sheathed, metal-clad, non?metallic-sheathed, or Type UF cables.
 
peter d said:
That rule is for conductors, not cables. No separation is required.

I frequently run doorbell and t-stat circuits in the same holes as NM cable.
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I agree. Sorry for the quick, incorrect answer
 
rlMutch said:
I agree. Sorry for the quick, incorrect answer
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No worries. We all make mistakes, and usually (OK, always) someone will pick up on it. You would be amazed at how much you learn this way!
 
peter d said:
No worries. We all make mistakes, and usually (OK, always) someone will pick up on it. You would be amazed at how much you learn this way!
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And if it doesn't work out that way, we wind up with a massively huge thread on whether the grounds go up or down :D

Oh, and Obligatory On-Topic-Remark -- thanks for the answers.
 
peter d said:
No worries. We all make mistakes, and usually (OK, always) someone will pick up on it.
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Sometimes, three in two minutes! :D

You would be amazed at how much you learn this way!
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Absolutely. :)

One other point to note, while we're talking low voltage and shared holes with NM cable: All the above posters were very specific in that they run doorbells and thermostats in the same hole.

Phone/Data cables such as Cat-5 and TV cables such as RG-6 should maintain a 24" seperation to avoid interference on them from the 120V line voltage 60 hz hum.

(Julie, this clarification was not for your benefit, but others who may be lurking, to be clear. :) )
 
georgestolz said:
Phone/Data cables such as Cat-5 and TV cables such as RG-6 should maintain a 24" seperation to avoid interference on them from the 120V line voltage 60 hz hum.
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In regards to the phone wire, I thought the twists cancel out any AC interference?

The phone cables on the poles run in parallel with high voltage AC lines for countless miles and seem to do fine. :)
 
georgestolz said:
Phone/Data cables such as Cat-5 and TV cables such as RG-6 should maintain a 24" seperation to avoid interference on them from the 120V line voltage 60 hz hum.

(Julie, this clarification was not for your benefit, but others who may be lurking, to be clear. :) )
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I'm not sure that's correct, particularly for data -- I run a TON of Cat5 right on top of 120 and 208 (we don't use 240, but I can't imagine 240 being any different) cabling at 1Gb/s and higher, with absolutely no interference. The reason, as we've discussed previously, is that UTP has the ability to self-correct for noise due to the way the conductors are twisted.

I suspect that properly shielded and constructed coax has even better noise rejection than UTP. Back in the day when Ethernet was run as either "thin net" (mostly RG-58 or RG-59, as I recall -- been a very long time) or "thick net" (some weird form of coax), I never saw power cable induced error problems. We ran our network cabling all over the floor, under the floor, in, on, binder-clipped to the ceiling along with our other cables.

The only low voltage cables I've seen that consistently hate being around power cabling is RS-232, but then it's more a question of the type of load than the voltage or even the current. Fluorescent lights are death for RS-232 cables.
 
iwire said:
In regards to the phone wire, I thought the twists cancel out any AC interference?
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Cat5 is UTP -- "unshielded twisted pair" -- and will cancel out AC interference. Some of the older telco wire isn't UTP and would pick up noise. Now that Cat5 is cheap I've seen Cat5 run instead of the unshielded and untwisted telephone wires of my youth ...

The phone cables on the poles run in parallel with high voltage AC lines for countless miles and seem to do fine. :)
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I thought those particular wires were shielded. You're talking about the cables that are about 1 1/2" in diameter, right?
 
iwire said:
In regards to the phone wire, I thought the twists cancel out any AC interference?
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tallgirl said:
The reason, as we've discussed previously, is that UTP has the ability to self-correct for noise due to the way the conductors are twisted.
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Technically speaking, the tight, consistent twists assure that both conductors of a pair pick up induced noise as similarly as possible, so the common-mode noise-rejection input circuitry (typically differential op-amps) can reject it.

All conductors can carry high-speed data streams. The greater the number of twists per foot, the higher the frequency (i.e., the shorter the wavelength) of noise that can be rejected, and thus the greater the reliable transfer rate.

Ever noticed that UTP cable pairs are twisted at slightly different rates? That's to minimize cross-talk among pairs in a given cable, as well as others in close proximity. UTP data cabling is practically immune to 60-Hz interference.

Added: By the way, for POTS (Plain-Old Telephone Service), CAT-3 is all that will ever be needed, and is all I ever run, for voice-only lines, unless I'm paid to run CAT-5e (or better) instead. We'll have optical before that's needed.
 
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I could be misinformed, I know that a 24" seperation is preached by the local LV gurus. I haven't done much research to confirm or deny their claims; I just said "okay" and began maintaining the seperation. :)
 
iwire said:
In regards to the phone wire, I thought the twists cancel out any AC interference?

The phone cables on the poles run in parallel with high voltage AC lines for countless miles and seem to do fine. :)
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Aren't the phone cables run about a foot or so apart from the power lines. This would allow them to be run parallel.
George our LV guys say 12" clearance--- who knows....
 
The rules in 725 are for conductors.
We are discussing a chapter 3 wiring method, NM cable
If you will accept that a door bell cable can be run in the same bored hole hole as RMC, or EMT, then the only logical conclusion is that it can be done with NM cable.
In some cases, such as a computer cable, its not a recommended practice.
 
tom baker said:
In some cases, such as a computer cable, its not a recommended practice.
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I'd like to see engineering data on that. This sounds like one of those things that people did back in the 70's and 80's and never stopped doing when it was no longer required. I know it was a problem back when we were using RS-232/422 for data, but I'm not convinced its a problem with coax, twinax or UTP.

Unshielded audio, sure -- keep audio cabling away from power, but a 60Hz power signal is nothing to a data signal being clocked at 400MHz, which I think is the clock frequency for 1000BaseT.
 
tallgirl said:
Unshielded audio, sure -- keep audio cabling away from power, but a 60Hz power signal is nothing to a data signal being clocked at 400MHz, which I think is the clock frequency for 1000BaseT.
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Even this is not an issue on the amplified side of audio. The low impedance of the speakers will null any noise which can cause a hum.

On the pre-amp side is where induced noise is an issue, or 60 cycle ground loops on non-commonly grounded MOSFET amps.
 
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