ceiling grid conduit mounting

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Coppersmith

Coppersmith

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Location
Tampa, FL, USA
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Electrical Contractor
I have a question about this section:

300.11 Securing and Supporting.
(B) Wiring Systems Installed Above Suspended Ceilings.
Cables and raceways shall not be supported by ceiling grids.

I worked a job where they installed a second ceiling grid system strictly for mounting electrical conduit and devices. There were no tiles installed in it. It was installed two or three feet above the actual ceiling. It was the exact same grid normally used for suspended ceilings.

Legal or not?
 
Is it possible the upper grid was the original one, and the lower one the new one?

Either way, I'd say the upper grid is not "the ceiling grid" and thus okay for support.
 
Answer still the same: there's only one ceiling, thus one ceiling grid.

The grids are separately supported, right?
 
In the strictest interpretation of that part of 300.11, that installation is not compliant - it doesn't say the ceiling grid, it says ceiling grids.

Two sentences before that though it says, and I quote:

" support wires and associated fittings that provide secure support and that are installed in addition to the ceiling grid support wires shall be permitted as the sole support"

Which in my humble opinion and code interpretation makes it legal IF the two ceiling grids had two completely separate sets of support wires.
 
I think the call could go either way. You have a secondary, auxiliary, or unused ceiling grid above a ceiling grid, but it is still a ceiling grid. If everything up there would stay in place if you remove the grid and just had the tie wires holding it in place, there would be no question whatsoever that it is code compliant.

I've only seen one building with a basic double grid system, and none of the electrical was supported by the original grid. The second, lower grid was added years later.

I would absolutely hate to rip all of that out because of a simple "the" missing from 300.11.
 
If the upper grid were installed solely for the support of the conduit then IMO it's up to the AHJ to decide if its strength is adequate to be used as means of support.
 
I did this job about 10 years ago and the reason I'm asking about it now is that I'm doing a "changes from NEC 2014" training, I read this section, and it caused me to think about that job.

If I am remembering correctly, the upper grid was separately supported from the lower, but it was not tied to the lower. It was attached to the walls as per normal. I should also note that we were laying conduit directly on top of the grid members.

After reading the responses so far, I'm tending to think this was not a ceiling grid. It was an independent conduit support system that just happened to be constructed out of ceiling grid material.
 
Coppersmith said:
I did this job about 10 years ago and the reason I'm asking about it now is that I'm doing a "changes from NEC 2014" training, I read this section, and it caused me to think about that job.

If I am remembering correctly, the upper grid was separately supported from the lower, but it was not tied to the lower. It was attached to the walls as per normal. I should also note that we were laying conduit directly on top of the grid members.

After reading the responses so far, I'm tending to think this was not a ceiling grid. It was an independent conduit support system that just happened to be constructed out of ceiling grid material.
Click to expand...
It may well be an independent support system, but IMHO supporting conduit or wires on the grid members rather than directly from the support wires is still a bad idea and a violation.

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GoldDigger said:
It may well be an independent support system, but IMHO supporting conduit or wires on the grid members rather than directly from the support wires is still a bad idea and a violation.

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Click to expand...

I agree. Ceiling grids are to support ceilings. It may be adequate to support coppersmith installation, however had he tried to use that grid to support multiple runs of say 2in IMC, it probably would have buckled those thin aluminum t bars and the whole thing would have come down if those conduits were not supported
directly by the support wires.

Some ceiling grids are strong enough to support fixtures, like a heavy-duty grid-like is in a commercial kitchen. Those drop tiles are heavier than sheetrock of an equal size. And lightweight devices, like smoke detectors, I believe can be supported by the grid, perhaps even the tile itself.

If I were the inspector on that job, I would have failed it, however I would not have made him remove the grid rather just install wires to the ceiling to support all of the conduits. At that point the grid is irrelevant and it's not supporting anything.

Eta: one of the first jobs I ever cable with v/d/v cable was a 44 room addition to a hotel that was up sizing and changing brands. Right before the rough-in inspection, my boss came by to see how everything was going. all of my cables, save for one we're all nicely and neatly bundled and supported, however this one cable had a bit of slack in it between 2 D-rings and was touching the grid. There was probably less than a gram of weight on that ceiling, however he made me pull it tight so that it was not touching the Grid at all. In that case though, one of the concerns is a firefighter poking an axe through the ceiling and getting it hung up in a wad of cable and bringing it all down on himself
 
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