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.
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, 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.)
Where does this silly idea come from? 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.
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.
In my area it is not allowed by the "silly inspectors". The inspectors reference the heating of the conduit which somehow diminishes the romex rating. I should not have advised the stripping of the romex jacket that came out wrong but I have been allowed an exception by inspectors to strip romex when leaving the building space to connect to the HVAC equipment 3 to
6 feet. This was done to meet the requirement of no jacketed wire in metal pipe. I now use non-metallic conduit exclusively for all residential applications, problem solved.
See other post for my clarification, it maybe allowed by code. Someone posted it about protecting the cable. I always error on the safe or over do it side of the fence.
I think I mis-spoke here as to stripping the romex, not a good idea. I meant that to go from romex to conduit you would have to go with individual conductors. I have to be more careful in posting here, and to be clear in the info given. I am an HVAC tech not electrician.
If the wiring method is conduit, single conductor is the cheaper way to go, so common sense kicks in here, right?
Help me here, where is it that it's not permissiable to use sheath nm in conduit where physical protection(you call "spot mechanical protection")? Book is big, and I'm learning everyday.
Nipples need to worry about conduit fill, just that you goto 60% column, instead of the others. I think the tiny-tiny piece for floor transistions is ignored, but once again, I have to check the notes in chaper 9.
You are mentioning Canada a lot, so maybe we are in different books.
- 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.
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