PVC Conduit in Walls

[bcorbin]

I have a 2-story medical office building that has most of the main feeders from the exterior main service distribution panel are run in PVC. It's an obvious code violation as it stands, as many of the conduits are run through return plenum space (not wrapped). Even if the plenum is converted to a ducted system, I am concerned about the "subject to physical damage" aspect of 352.12 still being a violation.

If a conduit is found to run vertically inside a wall, rather than through it, would this be considered "subject to physical damage"? It could be nailed into by accident, just like Romex (which luckily, we haven't found).

Or am I just being too cautious?

 

[Strife]

I would guess the same 1-1/4" rule would apply as rommex,

I have a 2-story medical office building that has most of the main feeders from the exterior main service distribution panel are run in PVC. It's an obvious code violation as it stands, as many of the conduits are run through return plenum space (not wrapped). Even if the plenum is converted to a ducted system, I am concerned about the "subject to physical damage" aspect of 352.12 still being a violation.

If a conduit is found to run vertically inside a wall, rather than through it, would this be considered "subject to physical damage"? It could be nailed into by accident, just like Romex (which luckily, we haven't found).

Or am I just being too cautious?

 

[Smart $]

I would guess the same 1-1/4" rule would apply as rommex,

Exception No. 1 to pertinent 300.4 subparagraphs alleviates the 1-1/4" requirement.

Steel plates, sleeves, or the equivalent
shall not be required to protect rigid metal conduit, intermediate
metal conduit, rigid nonmetallic conduit, or electrical
metallic tubing.

 

[Smart $]

... Even if the plenum is converted to a ducted system, I am concerned about the "subject to physical damage" aspect of 352.12 still being a violation. ...

What would cause the physical damage?

 

[bcorbin]

What would cause the physical damage?

It could be nailed into by accident

.

 

[Strife]

Which is kinda weird? don't you agree?
I mean PVC is prone to being penetrated just as well by a dry wall screw as rommex is???

Exception No. 1 to pertinent 300.4 subparagraphs alleviates the 1-1/4" requirement.

Steel plates, sleeves, or the equivalent
shall not be required to protect rigid metal conduit, intermediate
metal conduit, rigid nonmetallic conduit, or electrical
metallic tubing.

 

[bcorbin]

I do agree that on the surface it seems weird.

As in the high-rise residential I did a while back. I discovered that romex in the ceiling was indeed legal, but only if it wasn't exposed. (This was the kind of ceiling with a big suspended cloud in the middle...everything would have been painted black above it.)

I figure you'd have to be a real dummy to nail through exposed romex. Concealed? Definitely possible.

But I'm sure a bunch of guys smarter than me already thought it all through.

 

[cowboyjwc]

I'd be wondering more how you were getting your redundint grounding if the feeders are plastic.

 

[Smart $]

It could be nailed into by accident

It could... but the exception I noted alleviates additional protection requirement. To me, that says PVC concealed in a wall is not "subject to physical damage" of that type. Some discretion and moderation has to used when we consider what could cause physical damage. A plane could drop out of the sky and slam into any structure. Shall we consider this scenario as "subject to physical damage"???

 

[Smart $]

I'd be wondering more how you were getting your redundint grounding if the feeders are plastic.

Redundant grounding applies to feeders???

 

[kwired]

I'd be wondering more how you were getting your redundint grounding if the feeders are plastic.

May not feed patient care areas, all he said was "medical office building". Even so only branch circuits in patient care areas are required the redundant grounding. A feeder does not have be redundant grounding.

 

[bcorbin]

Smart$, I see your point about physical damage. The exception could definitely be interpreted that way.

You know, I didn't think about the redundant grounding, since they are feeders. However, there are a couple of outpatient (X-Ray, MRI, CT) care rooms in the building, so it's definitely something to keep an eye out for!

Thanks a bunch.

Designing things to code is a lot easier than spotting every little thing someone else built wrong. My sympathies (however brief ) to the inspectors out there.

 

[cowboyjwc]

May not feed patient care areas, all he said was "medical office building". Even so only branch circuits in patient care areas are required the redundant grounding. A feeder does not have be redundant grounding.

That's true, as long as they pulled a ground wire.

 

[kwired]

That's true, as long as they pulled a ground wire.

With PVC I would sure hope they pulled a ground no matter what it is feeding.

 

[cowboyjwc]

With PVC I would sure hope they pulled a ground no matter what it is feeding.

I'm an inspector, I wouldn't bring it up if I hadn't seen it before.

 

[kwired]

I'm an inspector, I wouldn't bring it up if I hadn't seen it before.

Well, if they would have used a bonding bushing on the PVC adapter with a nylon bonding jumper to the enclosure they would not have needed to pull a grounding conductor in the raceway unless it was supplying circuits in patient care areas:lol::lol:

 

[jaggedben]

I mean PVC is prone to being penetrated just as well by a dry wall screw as rommex is???

I wouldn't think so. I would think whereas romex would offer no resistance noticable to the drywaller, PVC in many or most cases would cause the screw to spin out or deflect it's direction. It depends somewhat on the size and schedule of the PVC of course, and also how much wood the screw passes through before hitting the PVC (less wood would actually be better).

 

[kwired]

I wouldn't think so. I would think whereas romex would offer no resistance noticable to the drywaller, PVC in many or most cases would cause the screw to spin out or deflect it's direction. It depends somewhat on the size and schedule of the PVC of course, and also how much wood the screw passes through before hitting the PVC (less wood would actually be better).

Don't be so sure about that, some drywall screws have pretty sharp tip and can zip right into EMT without the installer even knowing -- seen it before.

 

[jaggedben]

Don't be so sure about that, some drywall screws have pretty sharp tip and can zip right into EMT without the installer even knowing -- seen it before.

I used to be a theatrical carpenter and I've drive a lot of drywall screws in my time. Used them to attach PVC to things a few times too, and had to drill pilot holes. Of course in certain circumstances, I'm sure what you describe could happen, but it's a question of probabilities. I think EMT is stronger than PVC is stronger than romex when it comes to protecting against damage from screws. PVC offers some protection, romex essentially none.

 

[mjf]

I used to be a theatrical carpenter and I've drive a lot of drywall screws in my time. Used them to attach PVC to things a few times too, and had to drill pilot holes. Of course in certain circumstances, I'm sure what you describe could happen, but it's a question of probabilities. I think EMT is stronger than PVC is stronger than romex when it comes to protecting against damage from screws. PVC offers some protection, romex essentially none.

where and how romex is attached is really its only protection against the DDS (dreaded drywall screw). Unless the screw happens launch its attack real close to a fastener, the romex should have a little flexibility to move away from an attacking screw (key word is should).