Supporting MC cable above Suspended, Lay-in tile ceilings

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tx2step

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North Texas, DFW area
I'm under the 2002 code.

How do you guys support MC cable (or boxes, EMT, etc.) that you run above suspended, lay-in tile type ceilings? Most of them are return air plenums, so they're not fire rated.

300.11(A)(2) prohibits using the ceiling support wires unless you follow the ceiling system manufacturer's instructions. Have any of you read any of those? If so, what do they say? And if you're installing into an existing ceiling, how would you know how to find that info out?

Do you guys just install your own independent support wires, so you don't have to prove to the AHJ what the ceiling manufacturer instructions say?

Thanks!
 
tx2step said:
I'm under the 2002 code.

How do you guys support MC cable (or boxes, EMT, etc.) that you run above suspended, lay-in tile type ceilings? Most of them are return air plenums, so they're not fire rated.

300.11(A)(2) prohibits using the ceiling support wires unless you follow the ceiling system manufacturer's instructions. Have any of you read any of those? If so, what do they say? And if you're installing into an existing ceiling, how would you know how to find that info out?

Do you guys just install your own independent support wires, so you don't have to prove to the AHJ what the ceiling manufacturer instructions say?

Thanks!
Click to expand...

Ive always clamped bat wings on the support wires. Never gotten jammed up from an inspector for it.
 
The issue is usually when is enough, enough? Securing a fixture whip seems innocent enough but securing 5 - 10- 15- or 20 branch circuits tends to cause deflection - it would seem that the reason for the rule was abuse of wiring methods in which the support wires held up the ceiling grid as well as supporting electrical wiring. The manufactures instructions (not rocket science) are commonly a 4' max distance between support wires on a main beam, so if installed at the maximum distance separation the support wires would technically be installed for the ceiling only.
 
mwm1752 said:
The issue is usually when is enough, enough? Securing a fixture whip seems innocent enough but securing 5 - 10- 15- or 20 branch circuits tends to cause deflection - it would seem that the reason for the rule was abuse of wiring methods in which the support wires held up the ceiling grid as well as supporting electrical wiring. The manufactures instructions (not rocket science) are commonly a 4' max distance between support wires on a main beam, so if installed at the maximum distance separation the support wires would technically be installed for the ceiling only.
Click to expand...

I've never seen a ceiling manufacturer's installation instructions -- do they ever mention hanging electrical wiring from their wire support system?

Do you have a link to any of the ceiling manufacturer's installation instructions?

I don't think I've ever seen a grid system for 2x4 lay-in tiles that was supported any more often than at the corners of the tiles, so that wound be on 4' centers as a minimum -- maybe 8' sometimes... So technically, you could be red-tagged for using the ceiling support wires in most cases, right?

Especially of you are hanging multiple MC cables on some of the support wires?

Thanks!!!
 
mwm1752 said:
The issue is usually when is enough, enough? Securing a fixture whip seems innocent enough but securing 5 - 10- 15- or 20 branch circuits tends to cause deflection - it would seem that the reason for the rule was abuse of wiring methods in which the support wires held up the ceiling grid as well as supporting electrical wiring. The manufactures instructions (not rocket science) are commonly a 4' max distance between support wires on a main beam, so if installed at the maximum distance separation the support wires would technically be installed for the ceiling only.
Click to expand...

Yeah, I was referring pretty much exclusively to switch leg or lamp to lamp jumpers with the bat wings, my bad for not elaborating. If you have a trunk of branch circuits, I'm inclined to take those suckers all the way up. That being said, I don't think 30 bat wings clamped on to a single wire support drop would ever deflect it. Don't think there's enough tension there...

You do bring up a good question about support spacing, though. I have to admit that the weight difference between the lightest and heaviest drop tile I've seen is probably pretty staggering, but I've never actually observed if the heavier tiles require closer distance between supports. Interesting question.
 
tx2step said:
I'm under the 2002 code.

How do you guys support MC cable (or boxes, EMT, etc.) that you run above suspended, lay-in tile type ceilings? Most of them are return air plenums, so they're not fire rated.

300.11(A)(2) prohibits using the ceiling support wires unless you follow the ceiling system manufacturer's instructions. Have any of you read any of those? If so, what do they say? And if you're installing into an existing ceiling, how would you know how to find that info out?

Do you guys just install your own independent support wires, so you don't have to prove to the AHJ what the ceiling manufacturer instructions say?

Thanks!
Click to expand...
Get some beer or Dr. Pepper and a can of spray paint. Give the beer or Dr. Pepper to the ceiling guy and ask him for some grid wire. Spray paint the wire on the floor. Get some more beverages and ask your new ceiling guy friend if he will put them up for you.
 
ActionDave said:
Get some beer or Dr. Pepper and a can of spray paint. Give the beer or Dr. Pepper to the ceiling guy and ask him for some grid wire. Spray paint the wire on the floor. Get some more beverages and ask your new ceiling guy friend if he will put them up for you.
Click to expand...

I'm usually too busy yelling at them for putting mains down the centers of hallways to do that.:thumbsdown:
 
ActionDave said:
Get some beer or Dr. Pepper and a can of spray paint. Give the beer or Dr. Pepper to the ceiling guy and ask him for some grid wire. Spray paint the wire on the floor. Get some more beverages and ask your new ceiling guy friend if he will put them up for you.
Click to expand...


:thumbsup: A lot cheaper than buying a powder actuated pole tool.
 
tx2step said:
I've never seen a ceiling manufacturer's installation instructions -- do they ever mention hanging electrical wiring from their wire support system?

Do you have a link to any of the ceiling manufacturer's installation instructions?

I don't think I've ever seen a grid system for 2x4 lay-in tiles that was supported any more often than at the corners of the tiles, so that wound be on 4' centers as a minimum -- maybe 8' sometimes... So technically, you could be red-tagged for using the ceiling support wires in most cases, right?

Especially of you are hanging multiple MC cables on some of the support wires?

Thanks!!!
Click to expand...


http://www.bcceilings.com/seismic.pdf
 
ActionDave said:
Get some beer or Dr. Pepper and a can of spray paint. Give the beer or Dr. Pepper to the ceiling guy and ask him for some grid wire. Spray paint the wire on the floor. Get some more beverages and ask your new ceiling guy friend if he will put them up for you.
Click to expand...
I walk in and ask who is the ceiling god.
Then beer money or both.
I have never read grid cut sheets. I understood that if the grid installer is willing to take responsibility for allowing us to use his support as a means for us then its ok , but ive never heard one say sure hang all your crap on my wires till its all out of level.


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