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NEC question: low-voltage wiring crossing 120v wiring.



 
 
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  #1  
Old September 29th 11, 08:19 PM posted to alt.home.repair
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Posts: 764
Default NEC question: low-voltage wiring crossing 120v wiring.

I am running network cables -- shielded, if that makes a difference --
above suspended ceiling where there is already 120V Romex wiring in
places. This 120V wiring is stapled to the joists at intervals.

Is it OK for the network cables to lie on the ceiling support members,
and thus beneath the Romex? Or should the network cables be above the
Romex? Or should one or both be in conduit? -- more precisely, should
what is now Romex be redone with individual conductors in conduit?

Perce
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  #2  
Old September 29th 11, 10:30 PM posted to alt.home.repair
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Posts: 10,666
Default NEC question: low-voltage wiring crossing 120v wiring.

On Thu, 29 Sep 2011 15:19:42 -0400, "Percival P. Cassidy"
wrote:

I am running network cables -- shielded, if that makes a difference --
above suspended ceiling where there is already 120V Romex wiring in
places. This 120V wiring is stapled to the joists at intervals.

Is it OK for the network cables to lie on the ceiling support members,
and thus beneath the Romex? Or should the network cables be above the
Romex? Or should one or both be in conduit? -- more precisely, should
what is now Romex be redone with individual conductors in conduit?

Perce

no issue even with cat5 or cat5e non sheilded - as long as your space
above the ceiling is not an air plenum - and then you just need plenum
rated cat5
  #3  
Old September 30th 11, 01:07 AM posted to alt.home.repair
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Posts: 634
Default NEC question: low-voltage wiring crossing 120v wiring.

On Sep 29, 5:30*pm, wrote:
On Thu, 29 Sep 2011 15:19:42 -0400, "Percival P. Cassidy"

wrote:
I am running network cables *-- shielded, if that makes a difference --
above suspended ceiling where there is already 120V Romex wiring in
places. This 120V wiring is stapled to the joists at intervals.


Is it OK for the network cables to lie on the ceiling support members,
and thus beneath the Romex? Or should the network cables be above the
Romex? Or should one or both be in conduit? -- more precisely, should
what is now Romex be redone with individual conductors in conduit?



*no issue even with cat5 or cat5e non sheilded - as long as your space
above the ceiling is not an air plenum - and then you just need plenum
rated cat5


What's the reasoning behind plenum rating a computer cable? Is there
some fire-reasoning behind it or what? What's the difference between
rated and non-rated cable?

R
  #4  
Old September 30th 11, 03:43 AM posted to alt.home.repair
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Posts: 10,666
Default NEC question: low-voltage wiring crossing 120v wiring.

On Thu, 29 Sep 2011 17:07:32 -0700 (PDT), RicodJour
wrote:

On Sep 29, 5:30*pm, wrote:
On Thu, 29 Sep 2011 15:19:42 -0400, "Percival P. Cassidy"

wrote:
I am running network cables *-- shielded, if that makes a difference --
above suspended ceiling where there is already 120V Romex wiring in
places. This 120V wiring is stapled to the joists at intervals.


Is it OK for the network cables to lie on the ceiling support members,
and thus beneath the Romex? Or should the network cables be above the
Romex? Or should one or both be in conduit? -- more precisely, should
what is now Romex be redone with individual conductors in conduit?



*no issue even with cat5 or cat5e non sheilded - as long as your space
above the ceiling is not an air plenum - and then you just need plenum
rated cat5


What's the reasoning behind plenum rating a computer cable? Is there
some fire-reasoning behind it or what? What's the difference between
rated and non-rated cable?

R

Fire rating. Plenum cable will not support combustion when flame is
removed - will not flame on it's own - and different smoke. Non-plenum
rated is not allowed in an air return.
  #5  
Old September 30th 11, 04:58 AM posted to alt.home.repair
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Posts: 1,738
Default NEC question: low-voltage wiring crossing 120v wiring.

On 9/29/2011 2:19 PM, Percival P. Cassidy wrote:
I am running network cables -- shielded, if that makes a difference --
above suspended ceiling where there is already 120V Romex wiring in
places. This 120V wiring is stapled to the joists at intervals.

Is it OK for the network cables to lie on the ceiling support members,
and thus beneath the Romex? Or should the network cables be above the
Romex? Or should one or both be in conduit? -- more precisely, should
what is now Romex be redone with individual conductors in conduit?

Perce


the only thing they taught us to avoid is running parallel to high
current cables. But if you're using shielded cable, even that shouldn't
matter. And i don't imagine any cable in a house to be high current
except the range line and the line to the a/c unit. Lay away!

--
Steve Barker
remove the "not" from my address to email
  #6  
Old September 30th 11, 12:41 PM posted to alt.home.repair
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Posts: 1,582
Default NEC question: low-voltage wiring crossing 120v wiring.

On Sep 29, 8:07*pm, RicodJour wrote:
On Sep 29, 5:30*pm, wrote:





On Thu, 29 Sep 2011 15:19:42 -0400, "Percival P. Cassidy"


wrote:
I am running network cables *-- shielded, if that makes a difference --
above suspended ceiling where there is already 120V Romex wiring in
places. This 120V wiring is stapled to the joists at intervals.


Is it OK for the network cables to lie on the ceiling support members,
and thus beneath the Romex? Or should the network cables be above the
Romex? Or should one or both be in conduit? -- more precisely, should
what is now Romex be redone with individual conductors in conduit?


*no issue even with cat5 or cat5e non sheilded - as long as your space
above the ceiling is not an air plenum - and then you just need plenum
rated cat5


What's the reasoning behind plenum rating a computer cable? *Is there
some fire-reasoning behind it or what? *What's the difference between
rated and non-rated cable?

R- Hide quoted text -

- Show quoted text -


If it's a plenum that means something is pumping air through it to the
rest of the building. Can you think of a better way to speed
combustion and spread smoke he asked rhetorically?
  #7  
Old September 30th 11, 02:52 PM posted to alt.home.repair
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Posts: 630
Default NEC question: low-voltage wiring crossing 120v wiring.


"RicodJour" wrote in message
...
On Sep 29, 5:30 pm, wrote:
On Thu, 29 Sep 2011 15:19:42 -0400, "Percival P. Cassidy"

wrote:
I am running network cables -- shielded, if that makes a
difference --
above suspended ceiling where there is already 120V Romex wiring in
places. This 120V wiring is stapled to the joists at intervals.


Is it OK for the network cables to lie on the ceiling support
members,
and thus beneath the Romex? Or should the network cables be above
the
Romex? Or should one or both be in conduit? -- more precisely,
should
what is now Romex be redone with individual conductors in conduit?



no issue even with cat5 or cat5e non sheilded - as long as your
space
above the ceiling is not an air plenum - and then you just need
plenum
rated cat5


[What's the reasoning behind plenum rating a computer cable? Is there
some fire-reasoning behind it or what? What's the difference between
rated and non-rated cable?]

Some wire (non plenum rated), when it burns in a fire, will put off
toxic smoke. You wouldn't want toxic smoke to be sent through all the
air ducts!

  #8  
Old September 30th 11, 03:33 PM posted to alt.home.repair
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Posts: 97
Default NEC question: low-voltage wiring crossing 120v wiring.

On Sep 29, 5:30*pm, wrote:
On Thu, 29 Sep 2011 15:19:42 -0400, "Percival P. Cassidy"

wrote:
I am running network cables *-- shielded, if that makes a difference --
above suspended ceiling where there is already 120V Romex wiring in
places. This 120V wiring is stapled to the joists at intervals.


Is it OK for the network cables to lie on the ceiling support members,
and thus beneath the Romex? Or should the network cables be above the
Romex? Or should one or both be in conduit? -- more precisely, should
what is now Romex be redone with individual conductors in conduit?


Perce


*no issue even with cat5 or cat5e non sheilded - as long as your space
above the ceiling is not an air plenum - and then you just need plenum
rated cat5


If there is romex there already, then let's hope it isn't plenum
space.

Only in commercial buildings would I expect space above suspended
ceilings to be used as air plenum (return air is drawn through it on
its way back to the hvac system), and commercial building code
anywhere in N.America requires power conductors to be in conduit or
armored cable, and data cabling to be in either conduit (in which
case, it might not need to be plenum rated) or a cable tray, the
better to prevent it from collapsing into the space during a fire,
blocking egress and creating a hazard for firefighters. At least
that's how it was explained to me.

Single-family residential code doesn't say anything about low-voltage
cabling except that you can't put it in the same boxes as 120V.

Having said that, I think laying it onto the suspended ceiling, as I
understand the OP is proposing, is going to be a pain whenever someone
wants to lift a panel. I'd find some clips to tack it to the joists.

I wouldn't expect simple romex runs to be an interference problem for
data communications. Fluorescent ballasts, light dimmers, fan speed
controls and any kind of motor or switching power supply, maybe.

Chip C
Toronto
  #9  
Old September 30th 11, 04:23 PM posted to alt.home.repair
external usenet poster
 
Posts: 634
Default NEC question: low-voltage wiring crossing 120v wiring.

On Sep 29, 10:43*pm, wrote:
On Thu, 29 Sep 2011 17:07:32 -0700 (PDT), RicodJour









wrote:
On Sep 29, 5:30*pm, wrote:
On Thu, 29 Sep 2011 15:19:42 -0400, "Percival P. Cassidy"


wrote:
I am running network cables *-- shielded, if that makes a difference --
above suspended ceiling where there is already 120V Romex wiring in
places. This 120V wiring is stapled to the joists at intervals.


Is it OK for the network cables to lie on the ceiling support members,
and thus beneath the Romex? Or should the network cables be above the
Romex? Or should one or both be in conduit? -- more precisely, should
what is now Romex be redone with individual conductors in conduit?


*no issue even with cat5 or cat5e non sheilded - as long as your space
above the ceiling is not an air plenum - and then you just need plenum
rated cat5


What's the reasoning behind plenum rating a computer cable? *Is there
some fire-reasoning behind it or what? *What's the difference between
rated and non-rated cable?


R


Fire rating. Plenum cable will not support combustion when flame is
removed - will not flame on it's own - and different smoke. Non-plenum
rated is not allowed in an air return.


Yes, but my question was whether the OP's above-ceiling space is
actually a plenum. I had assumed the question was residential, a
basement and the space was not used for airflow. Granted, that's
reading a lot into it, but perhaps they were bad assumptions.

Here are some interesting (but boring!) videos of the different cable
ratings burning.
http://www.l-com.com/multimedia/vide....aspx?ID=13100
Quite a difference between plain vanilla PVC and rated cable.

R
  #10  
Old September 30th 11, 04:36 PM posted to alt.home.repair
external usenet poster
 
Posts: 764
Default NEC question: low-voltage wiring crossing 120v wiring.

On 09/30/11 11:23 am, RicodJour wrote:

I am running network cables -- shielded, if that makes a difference --
above suspended ceiling where there is already 120V Romex wiring in
places. This 120V wiring is stapled to the joists at intervals.


Is it OK for the network cables to lie on the ceiling support members,
and thus beneath the Romex? Or should the network cables be above the
Romex? Or should one or both be in conduit? -- more precisely, should
what is now Romex be redone with individual conductors in conduit?


no issue even with cat5 or cat5e non sheilded - as long as your space
above the ceiling is not an air plenum - and then you just need plenum
rated cat5


What's the reasoning behind plenum rating a computer cable? Is there
some fire-reasoning behind it or what? What's the difference between
rated and non-rated cable?


Fire rating. Plenum cable will not support combustion when flame is
removed - will not flame on it's own - and different smoke. Non-plenum
rated is not allowed in an air return.


Yes, but my question was whether the OP's above-ceiling space is
actually a plenum. I had assumed the question was residential, a
basement and the space was not used for airflow. Granted, that's
reading a lot into it, but perhaps they were bad assumptions.

Here are some interesting (but boring!) videos of the different cable
ratings burning.
http://www.l-com.com/multimedia/vide....aspx?ID=13100
Quite a difference between plain vanilla PVC and rated cable.


You are correct: this is a residential setting, with a suspended ceiling
installed in the basement.

Perce

 




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