Physical Damage

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kwired said:
Even RMC/IMC could potentially be subject to damage especially with the driveway thing and vehicles.

Where should one draw the line? I'm talking for just about anything not just driveways or RMC/IMC. Anything you install is potentially subject to physical damage, but not always at same probability.

Items on driveway side of house - probably not just too likely in most cases, but there is always some chance. How often will someone place vehicle that close to the house? They risk damaging other items as well if they do this, so in general they won't do it, it would be sort of rare occasion should it happen.

Something else already brought up - NM cable on surface, usually below 7 feet or so. Why is it automatically considered subject to physical damage? I've seen a lot of it that been exposed in such locations for decades and is in very good condition. If anything first foot or so above floor is where brooms, vacuums and such would be more frequently in use and maybe would possibly cause more damage.
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IMO, for something to be subject to physical damage, there has to be something specific, unusual, and exceptionally likely to cause damage to the wiring method. "I can come up with a scenario where the wiring damage method could be damaged" or "it's exposed" doesn't cut it.
 
electrofelon said:
IMO, for something to be subject to physical damage, there has to be something specific, unusual, and exceptionally likely to cause damage to the wiring method. "I can come up with a scenario where the wiring damage method could be damaged" or "it's exposed" doesn't cut it.
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When it comes to hazardous locations determination they make it clear that not everything needs to be a hazardous location (it’s not an absolute). 70E arc flash “hazard” states that an arc flash hazard exists only if conditions are likely to cause an arc and I will add that also it needs to include that serious injury is likely as it is in Annex A of OSHA 1910.269.

Honestly a lot of local as well as state jurisdictions are effectively all over the place due to this ambiguity when we should be able to easily come up with a list. It would seem to me that the easiest way to solve this is to define “subject to physical damage” in the Article 100 definitions. Personally I think “subject to physical damage” itself is extremely overly broad. For instance are we protecting against crush and impact damage? If so there are big differences between say MC or TCER, as compared to even EMT or just cables in tray. And the various grades of cord (“extra hard usage”) are similarly undefined. And even the strongest raceway, IMC, has limits against physical damage. Nothing, not even concrete filled bollards, is dozer or fork truck driver proof. And this does not include sunlight, oil, water, or chemical resistance which may or may not be affected by raceway choice.

I’m not entirely opposed to being more aggressive towards NM. It is abused heavily. I also can’t really figure out what ENT is for. It’s really just a way of disguising conductors, not much more than the outer jacket on a cord.

The driveway example is kind of silly. There are engineering standards which deal specifically with road crossings and casements. Realistically you need to bury it deep enough based on the load or else use thicker casements. Ductile iron and concrete casements come in different thicknesses for this reason. Dirt contractors are supposed to know this. It is quite literally tables.

NFPA goes overboard on things like fire ratings on construction materials and hazardous locations yet utterly fails to define physical damage limits.
 
The areas where I would consider NM to be subject to physical damage have changed over the years. The jacket on NM in the 70s and 80s would take a lot more abuse without damage than the jacket in the currently available NM.
 
OK......My definition of subject to physical damage. Any wiring method fastened on an exposed surface in a shooting range is subject to physical damage. A #4 GEC fastened to the exterior of a dwelling is not. Please enlighten my AHJ.
 
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