liquid tight flex conduit strapped to roof top exhaust duct

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I mentioned kitchen exhaust ducting because you shouldn't just puncture it with sheet-metal screws, I've been told.
 
oldsparky52 said:
Most likely structurally capable of the added weight of some flex and wire (plus the fixture on top).
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Probably. I'm not really concerned about it "being able to support it." That's pretty much a duh. I'm just being nit picky about the idea of fastening things to the building structure as opposed to equipment.

I believe there are exceptions to this rule, but I've always been told "it needs to be securely fastened to the building structure." I believe it's mentioned somewhere in the early 300's. Then again, we do it all the time with disconnect switches on HVAC units. So I'm not really sure where the line is to be honest. All I know is there's a lot of stress about fastening things to the structure as opposed to equipment and that equipment is not a structure.
 
Jerramundi said:
Probably. I'm not really concerned about it "being able to support it." That's pretty much a duh. I'm just being nit picky about the idea of fastening things to the building structure as opposed to equipment.

I believe there are exceptions to this rule, but I've always been told "it needs to be securely fastened to the building structure." I believe it's mentioned somewhere in the early 300's. Then again, we do it all the time with disconnect switches on HVAC units. So I'm not really sure where the line is to be honest. All I know is there's a lot of stress about fastening things to the structure as opposed to equipment and that equipment is not a structure.
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When's the last time you looked up "structure" in the NEC definitions? :)

By the NEC definition, that duct could be considered a "structure".
 
j2020 said:
That's the reason why I am asking. I wasn't sure if there would be a code violation screwing in straps to the exhaust fan shaft housing going that far up.
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Probably not an NEC violation, that don't mean there can't be a violation of some other code related to what this exhaust stack is for, or just plain a bad idea if it will effect performance in some way.
 
Jerramundi said:
Huh, I would have never thought using magnets would be acceptable... in any circumstances...
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Better not go up on a commercial roof then where conduits are just strapped to durablocks that just so on the roof by gravity. Actually gravity is the weakest of the fundamental forces. If the strong force has a force of 1, the gravitational force is an astoundingly small 10^-41. The electromagnetic force is 10^-3. 😁
 
oldsparky52 said:
When's the last time you looked up "structure" in the NEC definitions? :)

By the NEC definition, that duct could be considered a "structure".
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When is the last time you looked it up? ;)

It's true that there WAS significant room for interpretation in the NEC definition of a "structure" as that which is "built or constructed" could mean literally anything and I mean ANYTHING, lol.

But the 2017 code change clarified this definition to NOT include equipment.

I think it's common sense that metal duct work IS equipment and NOT structure, but I suppose if you wanted to play lawyer, you could make a few semantic arguments to the contrary... especially pre-2017 code change. Post 2017 NEC, it's a little more difficult.

But again, I'm just being nit picky because we fasten disconnect switches to HVAC equipment all the time, so like I said, I'm not really sure where the line technically is.

None of this addresses the ambiguity between (1) the OP Title, which refers to this installation as a duct... and (2) the OP Post, which refers to this installation as a "shaft," as pointed out correctly by @gadfly56. I think of a shaft as being structural, whether it carries the exhaust or just houses the duct... and a duct as being equipment.
 
Like I said, I'm not sure where the line technically is... and I actually may be wrong about this particular instance after quickly parsing 300.

I'm not sure where I got the idea that supported by the building structure as opposed to equipment was required... I suppose it's just another case of the game of telephone played by contractors and yet another reason why reading the code for yourself is important.

I think I may be making too much of a generality out of securing and support requirements. There are instances in which cables and raceways explicitly require support by the structure... but it seems it's more general in most instances and just requires being "securely fastened in place."
 
Jerramundi said:
When is the last time you looked it up? ;)

It's true that there WAS significant room for interpretation in the NEC definition of a "structure" as that which is "built or constructed" could mean literally anything and I mean ANYTHING, lol.

But the 2017 code change clarified this definition to NOT include equipment.

I think it's common sense that metal duct work IS equipment and NOT structure, but I suppose if you wanted to play lawyer, you could make a few semantic arguments to the contrary... especially pre-2017 code change. Post 2017 NEC, it's a little more difficult.

But again, I'm just being nit picky because we fasten disconnect switches to HVAC equipment all the time, so like I said, I'm not really sure where the line technically is.

None of this addresses the ambiguity between (1) the OP Title, which refers to this installation as a duct... and (2) the OP Post, which refers to this installation as a "shaft," as pointed out correctly by @gadfly56. I think of a shaft as being structural, whether it carries the exhaust or just houses the duct... and a duct as being equipment.
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Equipment is built or constructed as well, but you need to use NEC definition of equipment and not the general definition, take another look at that definition it says "used as a part of, or in connection with, an electrical installation". So the metal duct that is not part of the electrical installation is not "equipment" from NEC perspective. As I mentioned earlier there could be other codes that also apply to this that would prohibit foreign objects being attached to this, there just is no violation of NEC going on here.
 
kwired said:
Equipment is built or constructed as well, but you need to use NEC definition of equipment and not the general definition, take another look at that definition it says "used as a part of, or in connection with, an electrical installation". So the metal duct that is not part of the electrical installation is not "equipment" from NEC perspective. As I mentioned earlier there could be other codes that also apply to this that would prohibit foreign objects being attached to this, there just is no violation of NEC going on here.
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Well, ultimately it's only relevant if there is something in the code that EITHER (1) RESTRICTS the OP's installation from being "secured and supported" by equipment AND/OR (2) REQUIRES the OP's installation to be "secured and supported" by the "structure."

I already clarified that I was taking "securing and supporting" requirements too far. That there are instances in which the means of "securing and supporting" has to be "structural," but that generally it's only required to be "securely fastened in place."

I looked through the article on liquid tight and it's just "securely fastened in place" as far as I can tell. There's nothing that requires it to be "secured/supported to/by a structure." But I didn't look at junction boxes and fixture support... Two other areas that could potentially be relevant.
 
kwired said:
Equipment is built or constructed as well, but you need to use NEC definition of equipment and not the general definition, take another look at that definition it says "used as a part of, or in connection with, an electrical installation". So the metal duct that is not part of the electrical installation is not "equipment" from NEC perspective. As I mentioned earlier there could be other codes that also apply to this that would prohibit foreign objects being attached to this, there just is no violation of NEC going on here.
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Yes, equipment is "built or constructed" as well and that created some overlap between "equipment" and "structure" in previous editions of the code. But that's why I was bringing up the 2017 code change to the definition of a "structure" to NOT include "equipment." So we can now confidently conclude that "equipment," as defined by the NEC, is EXCLUDED from the NEC definition of a "structure."

So the next step is to look at the NEC definition of "equipment" to confirm what exactly is excluded from the definition of a "structure." Should HVAC duct NOT be excluded from the definition of a "structure" by NOT meeting the definition of "equipment," YES.. I suppose you could argue that the duct now meets the definition of a "structure" as it most certainly is "built or constructed." However, this is conditional upon an HVAC duct NOT meeting the definition of "equipment."

So, let's look at the definition of equipment. As you correctly point out, the NEC definition of "equipment" is that which is "...used as a part of, or in connection with, an electrical installation."

Based on that PARTIAL definition of "equipment" alone, I would argue that an HVAC duct IS in fact "used as a part of, or in connection with, an electrical installation," DOES meet the definition of "equipment," and thus is NOT a "structure."

But let's say that leaves you unconvinced. You've only provided a portion of the definition of "equipment." The complete definition is as follows:

Equipment. A general term, including fittings, devices, appliances, luminaires, apparatus, machinery, and the like used as a part of, or in connection with, an electrical installation.

Is that which powers the movement of air not an "appliance" per the NEC definition of an "appliance" as "utilization equipment?" Thus, the HVAC duct could be considered an "appliance" as it is intrinsically part of something that IS "utilization equipment," thus making the HVAC duct meet the definition of "equipment" and therefore be excluded from the definition of a "structure."

But let's say you're STILL unconvinced and want to argue that the "utilization" is not performed in the duct itself. *headdesk* There is more to make the case for HVAC duct being "equipment."

The NEC doesn't define "apparatus" or "machinery" and so the only logical thing to do is to use the socially agreed upon terminology (i.e. that which is in the dictionary) outside of the NEC.

Merriam-Webster defines an "apparatus" as (a) "a set of materials or equipment designed for a particular use," and (c) "an instrument or appliance designed for a specific operation." So I would argue that the HVAC duct is part of an "apparatus," further qualifying it as "equipment," and thus NOT a "structure."

Besides all of the above, there's the "common sense" argument to be made. If you're searching for HVAC supplies... are you more likely to call them "HVAC equipment" or "HVAC structure?"

Ultimately there are MULTIPLE logical arguments to be made that an HVAC duct IS in fact "equipment" and thus NOT a "structure," but ultimately, as I previously posted, it is only relevant if there is something in the code that EITHER (1) RESTRICTS the OP's installation from being "secured and supported" by equipment AND/OR (2) REQUIRES the OP's installation to be "secured and supported" by the "structure."

It's your typical semantic debate that we seem to love, lol. IMO, all of the above dictates that an HVAC duct is "equipment" and NOT a "structure."
 
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