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electrical cable next to heating ducts



 
 
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  #1  
Old March 7th 05, 01:36 AM
Chris
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Default electrical cable next to heating ducts

I am trying to run a new electrical line but have a tight space where there
is a heating duct. That brings the cable close and potentially touching the
house heating duct. I saw a reference to cables in such a situation
requiring insulation or 1" air space.

What kind of insulaiton would you use. Household fibreglass? or is there
some special requirements.

Thanks
Chris


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  #2  
Old March 7th 05, 03:02 AM
TURTLE
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Default


"Chris" wrote in message
...
I am trying to run a new electrical line but have a tight space where there is
a heating duct. That brings the cable close and potentially touching the house
heating duct. I saw a reference to cables in such a situation requiring
insulation or 1" air space.

What kind of insulaiton would you use. Household fibreglass? or is there some
special requirements.

Thanks
Chris


This is Turtle.

I would try Wire hangers and a 1" air space. Anything less than 1" of air space
is less that what should be done. So you may try running the wire in flex
condiut till it passes the duct pipe and then pull the conduit away from the
duct with hangers as much as you can or get the 1" air space.

TURTLE


  #3  
Old March 7th 05, 03:17 AM
Chris
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Default

Don't think I have 1" of space, so would flex conduit work even if it was
close to the heating ducts
Thanks
Chris
"TURTLE" wrote in message
.. .

"Chris" wrote in message
...
I am trying to run a new electrical line but have a tight space where
there is a heating duct. That brings the cable close and potentially
touching the house heating duct. I saw a reference to cables in such a
situation requiring insulation or 1" air space.

What kind of insulaiton would you use. Household fibreglass? or is there
some special requirements.

Thanks
Chris


This is Turtle.

I would try Wire hangers and a 1" air space. Anything less than 1" of air
space is less that what should be done. So you may try running the wire in
flex condiut till it passes the duct pipe and then pull the conduit away
from the duct with hangers as much as you can or get the 1" air space.

TURTLE



  #4  
Old March 7th 05, 03:40 AM
Joseph
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Posts: n/a
Default


"Chris" wrote in message
...
Don't think I have 1" of space, so would flex conduit work even if it was
close to the heating ducts
Thanks
Chris


Turtle, let me add that if you are using romex you have to strip the
jacket off to go into a metal conduit. Also if you use metal conduit you
need to box both ends and ground the boxes and pipe. I would recommend a
non metallic conduit and go for it. If you put the "electrical line" in
conduit you can strap it right to the duct if you want. (Your codes may
very.)

Joseph


"TURTLE" wrote in message
.. .

"Chris" wrote in message
...
I am trying to run a new electrical line but have a tight space where
there is a heating duct. That brings the cable close and potentially
touching the house heating duct. I saw a reference to cables in such a
situation requiring insulation or 1" air space.

What kind of insulaiton would you use. Household fibreglass? or is

there
some special requirements.

Thanks
Chris


This is Turtle.

I would try Wire hangers and a 1" air space. Anything less than 1" of

air
space is less that what should be done. So you may try running the wire

in
flex condiut till it passes the duct pipe and then pull the conduit away
from the duct with hangers as much as you can or get the 1" air space.

TURTLE





  #5  
Old March 7th 05, 04:19 AM
Chris
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Posts: n/a
Default

Thanks for the insight. Is the conduit fairly flexible as I also have a
tight bend to deal with
Chris


"Joseph" wrote in message
...

"Chris" wrote in message
...
Don't think I have 1" of space, so would flex conduit work even if it was
close to the heating ducts
Thanks
Chris


Turtle, let me add that if you are using romex you have to strip the
jacket off to go into a metal conduit. Also if you use metal conduit you
need to box both ends and ground the boxes and pipe. I would recommend a
non metallic conduit and go for it. If you put the "electrical line" in
conduit you can strap it right to the duct if you want. (Your codes may
very.)

Joseph


"TURTLE" wrote in message
.. .

"Chris" wrote in message
...
I am trying to run a new electrical line but have a tight space where
there is a heating duct. That brings the cable close and potentially
touching the house heating duct. I saw a reference to cables in such a
situation requiring insulation or 1" air space.

What kind of insulaiton would you use. Household fibreglass? or is

there
some special requirements.

Thanks
Chris

This is Turtle.

I would try Wire hangers and a 1" air space. Anything less than 1" of

air
space is less that what should be done. So you may try running the wire

in
flex condiut till it passes the duct pipe and then pull the conduit
away
from the duct with hangers as much as you can or get the 1" air space.

TURTLE







  #6  
Old March 7th 05, 11:28 AM
Doug Miller
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Default

In article , "Joseph" wrote:
Turtle, let me add that if you are using romex you have to strip the
jacket off to go into a metal conduit.


Code cite, please? Unless that's a change in the 2002 Code, I believe you're
mistaken.

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?
  #7  
Old March 7th 05, 05:11 PM
The Real Tom
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Default

On Mon, 07 Mar 2005 01:17:15 -0500, wrote:

Where does this silly idea come from?


Don't know! Our state hasn't adopted 2005 NEC yet, the 2002 is still
the governing version. This will change in a few months.

But.... I've heard this so many times, to not put NM in conduit. When
right in ART 334 says you need to do it, when tranversing floors and
tells you to do it where physical protection is needed. Even a note
in Chapter 9 explains how to calculate size when using an
multiconnductor cable for conduit sizing.

To reiterate, I hear from any seasoned electricians, no cables in
conduit. The stick to their stories even after looking at the book,
but then, I guess they have to do what the boss says.

later,

tom @
www.MedicalJobList.com


The 2005 code has specifically addressed this saying it is OK to put
cables in raceways. In fact stripping the jacket off voids the
listing.
As for the "fishing" question, look into"MC" cable. This is an
assembled cable in a spiral flex aluminum jacket.


On Sun, 6 Mar 2005 19:40:47 -0800, "Joseph"
wrote:

urtle, let me add that if you are using romex you have to strip the
jacket off to go into a metal conduit.


  #9  
Old March 7th 05, 05:33 PM
Goedjn
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Default


Turtle, let me add that if you are using romex you have to strip the
jacket off to go into a metal conduit.


The only time you should be stripping the jacket off romex is
when you've decided to use it for sculpture.

Can't you just use THHN cable? I'd be mildly surprised
if the heating duct operated in excess of 160F.

--Goedjn
  #10  
Old March 7th 05, 06:44 PM
Chris Lewis
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Default

According to The Real Tom Tom @ www.WorkAtHomePlans.com:

But.... I've heard this so many times, to not put NM in conduit. When
right in ART 334 says you need to do it, when tranversing floors and
tells you to do it where physical protection is needed. Even a note
in Chapter 9 explains how to calculate size when using an
multiconnductor cable for conduit sizing.


It boils down to something like this:

- you have to consider "conduit fill" (possible overheat
issues) and potentially conductor derating.
- when the wiring system _needs_ to be in conduit (ie: Chicago codes,
or hazardous location rules), you must use unsheathed cable. You
can't get away with stripping the sheath off and running individual
conductors. It's no longer a "permitted" use of the wire...
- when you're using it for "spot mechanical protection" of
a system that's otherwise permissible as NM, inspectors will give
you a certain amount of leeway. This is partially codified
(IIRC a 1-2' limit on "sleeves" without having to worry about
conduit fill), and partially "inspector permitted".
- whatever you do, they'll be concerned that it's done without
damaging the cable (eg: cable pulling grease if necessary)

For example, I've had inspectors approve 3-6' "drops" of NM
sheathed cable in PVC electrical conduit[*]. Mostly 14/2 (wg for
the Americans ;-) in 1/2" PVC, but also several of 14/3 and
even one of 10/3 also in 1/2" PVC.

[Note that in no case is there more than 3 current carrying
conductors in the PVC - the sheath wouldn't let you...]

In Canada, we also have a provision by which we can bury NMW
(aka UF, looks just like ordinary NM, only heavier) in PVC
black irrigation tubing (as long as it's the CSA-approved grade),
to reduce burial depth requirements by 6".

In both cases, while the length of conduit is longer than the 1-2',
the inspector knows that a free-air conduit on a wall is going
to be okay heat-wise, and buried system will generally not
have trouble with heating either.
[*] wired garage NM on ceiling, since walls already finished, the
shop outlets and switches are on PVC conduit "drops" on the
inside wall face to provide mechanical protection agains the
wall.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
 




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