Wiring method for above ceiling grid

[rc/retired]

Everyone knows romex is the most deadliest wiring there is.

I feel silly. Dang!

Ron

 

[don_resqcapt19]

Is possible to have occupancy where NM cables can be used, but NM cable is not allowed in suspended ceilings other than in dwellings. Why dwellings, IDK. I mean we sleep at night in dwellings and is not a problem but most other places we don't sleep there but it is apparently a fire/smoke hazard if not in a dwelling??

It was all part of the horse trading that took place to get rid of the old 3 story limitation for NM. Much of the discussion centered around physical damage to the NM, with the idea that while the building is being constructed, there is more likelihood of physical damage to the NM above non-dwelling ceilings because of the other systems that are often installed above those ceilings.

I don't recall much discussion of the fire/smoke issue, and there really should not be, as there is a much greater fire/smoke hazard from the finishes and furnishings of the structure than from the electrical and mechanical systems installed using non-metallic methods.

 

[kwired]

We install MC Lite in contact with concrete all of the time without issue. There would need to be some other factor (like a corrosive environment, water intrusion, etc.) involved for it to corrode.

same here

 

[kwired]

It was all part of the horse trading that took place to get rid of the old 3 story limitation for NM. Much of the discussion centered around physical damage to the NM, with the idea that while the building is being constructed, there is more likelihood of physical damage to the NM above non-dwelling ceilings because of the other systems that are often installed above those ceilings.

I don't recall much discussion of the fire/smoke issue, and there really should not be, as there is a much greater fire/smoke hazard from the finishes and furnishings of the structure than from the electrical and mechanical systems installed using non-metallic methods.

I guess that makes some sense, but only slightly IMO.

 

[electrofelon]

I have never understood what is supposed to be so great about MC. All it has is that thin aluminum wrap over it. It crushes easily. Kink it and then you have exposed inner conductors and a bunch of sharp edges. It is definitely better for rodent resistance though I will give it that.

 

[letgomywago]

I have never understood what is supposed to be so great about MC. All it has is that thin aluminum wrap over it. It crushes easily. Kink it and then you have exposed inner conductors and a bunch of sharp edges. It is definitely better for rodent resistance though I will give it that.

It's MCwiring just like a Mc-coffee so you put MC before it and it's supposed to taste better. And the MCap is supposed to come extra crispy.

 

[letgomywago]

In all seriousness mc will ground out faster if cut and won't scrape off the sheathing and insulation if pulled against metal t bar like NM can

 

[electrofelon]

In all seriousness mc will ground out faster if cut and won't scrape off the sheathing and insulation if pulled against metal t bar like NM can

Sure, I can imagine certain situations, like abrasion type damage where MC is better, but I can see other situations where NM would be better.

 

[letgomywago]

Sure, I can imagine certain situations, like abrasion type damage where MC is better, but I can see other situations where NM would be better.

I agree. NM has a smaller profile and when installed correctly I think is tighter to the ceiling finish than MC is. Mc ends up on batwings and those slide down and so forth so you end up with spaghetti up there. I also think people are more fearfully of damaging it so don't walk on it but people use mc as a ladder or even as a place to strap their work to.

 

[ramsy]

see UL categories (AALC) and (PJAC)

PJAZ describes MC Cable

"Cable marked for direct burial is also considered acceptable for encasement in concrete."

I believe direct burial is underground, a wet location per AALZ below.

Cable with a nonmetallic outer jacket that complies with the Limited Smoke Test requirements specified in UL 1685, ‘‘Vertical-Tray Fire-Propagation and Smoke-Release Test for Electrical and Optical-Fiber Cables,’’ and all unjacketed metal-clad cable may be marked with the suffix ‘‘-LS."

AALZ - INSTALLATION REQUIREMENTS for Ordinary locations, as defined in the NEC, include:

Damp Location — Partially protected locations under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderate degrees of moisture, such as some basements, barns, and cold-storage warehouses.

Wet Location — Installations underground or in concrete slabs or masonry in direct contact with the earth, and locations subject to saturation with water or other liquids, such as vehicle washing areas, and locations exposed to weather and unprotected

 

[roger]

PJAZ describes MC Cable

"Cable marked for direct burial is also considered acceptable for encasement in concrete."

I believe direct burial is underground, a wet location per AALZ below.

Cable with a nonmetallic outer jacket that complies with the Limited Smoke Test requirements specified in UL 1685, ‘‘Vertical-Tray Fire-Propagation and Smoke-Release Test for Electrical and Optical-Fiber Cables,’’ and all unjacketed metal-clad cable may be marked with the suffix ‘‘-LS."

AALZ - INSTALLATION REQUIREMENTS for Ordinary locations, as defined in the NEC, include:

Damp Location — Partially protected locations under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderate degrees of moisture, such as some basements, barns, and cold-storage warehouses.

Wet Location — Installations underground or in concrete slabs or masonry in direct contact with the earth, and locations subject to saturation with water or other liquids, such as vehicle washing areas, and locations exposed to weather and unprotected

Correct, for damp and wet locations you would have to use a proper cable. As I said, if the MC lite leaves a dry location you would have to make a transition at that point.

 

[roger]

I have never understood what is supposed to be so great about MC. All it has is that thin aluminum wrap over it. It crushes easily. Kink it and then you have exposed inner conductors and a bunch of sharp edges. It is definitely better for rodent resistance though I will give it that.

We probably used as much steel MC as Al.

 

[electrofelon]

We probably used as much steel MC as Al.

I don't think steel MC is commonly available any of the places I work. I don't think I've ever even seen it. Definitely much tougher.

 

[roger]

I don't think steel MC is commonly available any of the places I work. I don't think I've ever even seen it. Definitely much tougher.

Another regional issue I guess. We could walk into any supply house and ask for either.

 

[electrofelon]

Another regional issue I guess. We could walk into any supply house and ask for either.

What about AC cable, is that common down there? That is also pretty much non-existent here, most of the supply house guys will look at you like you have two heads if you ask for it.

 

[roger]

What about AC cable, is that common down there? That is also pretty much non-existent here, most of the supply house guys will look at you like you have two heads if you ask for it.

AC itself is not common however, most HCFC is the AC version not MCAP. I never purchased MCAP and have never actually seen it.

 

[roger]

I have to take back never having seen it. I do remember having a few rolls on a small healthcare facility once.

 

[electrofelon]

I actually kinda have always hated MC. I much prefer AC or MCAP and not having to deal with added work of making up EGC's. And those cables should be substantially cheaper than MC in theory (but I don't think they are presumably because of the massive amounts of MC made). Of course almost everyone is a grounding nut these days so probably prefer MC, so it's probably unlikely we will ever get back to an AC type cable as being the standard.

 

[roger]

so it's probably unlikely we will ever get back to an AC type cable as being the standard.

And that's a shame.

 

[don_resqcapt19]

AC itself is not common however, most HCFC is the AC version not MCAP. I never purchased MCAP and have never actually seen it.

I think AC is common in the New York City area, but not so much in the rest of the country.