MC Support above Suspended Ceiling

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mkgrady

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Location
Massachusetts
In this office remodel I need to run MC above a suspended ceiling. What I usually find is that securing MC to the bar joists works pretty well but in this case there are no bar joists. The construction is fireproofed steel beams below the corrugated decking with the drop ceiling about 4-1/2 feet below the deck. The beams look to be about ten feet apart. There doesn't seem to be a good place to secure the MC cables. In fact the whole office seems to be wired in MC with hardly any support of the cables above the ceiling. Much of the existing MC is not being touched by me but I won't be surprised if an inspection will cause the owner to have to deal with this.

The existing ceiling is held up with typical wire that have clips shot in to the deck. Much of the ceiling will be taken down and reconfigured for the new space. The only way I can think to support an new MC is to shoot a clip and drop wire into the deck every six feet and attach new MC to it at a height a foot or two above the ceiling, but how do I keep the support wire from swinging around freely without a ceiling to attach the bottom end to? Is there an easier way to do this?
 
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mkgrady

Senior Member
Location
Massachusetts
Nom Deplume said:
Check 300.11(A) and the MA amendment. That was for the 2011, I'm not sure if it the same for 2014.
Click to expand...

Thanks, for 2014 it did not change and it says I can attach to the ceiling grid support wires. I did not know we could do that in Mass. Are tie wraps acceptable for attaching the MC to the support wire? I have seen clips made by Caddy but tie wraps seem easier.
 
infinity

infinity

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Location
New Jersey
Occupation
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We use these, holds about 6 cables fastened to the deck. OK unless there is a roof above the deck.

Erico-CDYMCS50-55346_ZM.jpg

https://www.gexpro.com/support-brac...-ac-cable-support-spacer-4-runs/product/81153
 
infinity

infinity

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Location
New Jersey
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Yes, it gets anchored to the deck. We may also attach them to the bottom of a conduit rack if available and no more than 6' apart.
 
Fulthrotl

Fulthrotl

~Autocorrect is My Worst Enema.~
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mkgrady said:
Thanks, for 2014 it did not change and it says I can attach to the ceiling grid support wires. I did not know we could do that in Mass. Are tie wraps acceptable for attaching the MC to the support wire? I have seen clips made by Caddy but tie wraps seem easier.
Click to expand...

the only problem is, are the ty wraps approved for the purpose?
i've seen inspectors turn down ty wraps above the t bar if they aren't fireproof,
which i don't think most of them are.

the caddy k-8 clips do a spiffy job, except in calif. where they decided that
you can't attach to the ceiling wires anymore, so you have to shoot in wires.
 
jaylectricity

jaylectricity

Senior Member
Location
Massachusetts
Occupation
licensed journeyman electrician
Tie wraps are fine. Hell, electrical tape is fine. I don't believe support has to be listed for anything. It just has to be that beautiful word "adequate".
 
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NewGuy111

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Location
San Jose, CA
don_resqcapt19

don_resqcapt19

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Staff member
Location
Illinois
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retired electrician
Fulthrotl said:
...
i've seen inspectors turn down ty wraps above the t bar if they aren't fireproof, which i don't think most of them are. ...
Click to expand...
That would be an issue only if the above the ceiling space is a 300.22(C) space. Even if it is a 300.22(C) space look closely at the information on the package, many of the standard wire ties are suitable for use in 300.22(C) spaces and they are much cheaper. I looked at one brand where their standard wire tie said it was permitted to be installed in 300.22(C) spaces and that wire tie costs about 5 cents. The same manufacture has a "plenum" wire tie that costs 81 cents. They want you to buy the more expensive one, but there is no need to do that.
 
J.P.

J.P.

Senior Member
Location
United States
Cooper makes a BW-8 for attaching mc or 1/2 " emt to tie wire. The BW-12 will handle 3/4" emt. Batwings are what they are called in my area.

As far as zip tie's I think they are fine to use. The batwings are cleaner.

I do believe you have to have your own grid wire that is identified and secured at both ends for your electrical though. You can loosely secure it to the grid on the bottom. Just don't go overboard and pull the grid out of whack.

We paint both ends of our wire orange for a foot or so in order to identify it.
 
joebell

joebell

Senior Member
Location
New Hampshire
I find this Mass ammendment a little confusing. They delete the third sentence that speaks to adding independent support wires, yet the fourth sentence continues the independent support wire requirement.

I thnk when dealing with this section you have to read a little further and decide if you are dealing with (A)(1) or (A)(2) type of ceiling.

The Fire rated ceiling in (A)(1) requires independent support wires attached to the grid as long as they are "distinguisable" from the ceiling support wires

Similar language appears in section (A)(2) but this is ammended in MA to allow branch circuit wiring associated with equipment located within, attached to, or supportted by, to be allowed to be supported by the ceiling support wires. IMO this includes lighting branch circuits or misc. HVAC equipment located above the drop ceiling, and would exclude cables run for feeders or branch circuits for wall receptacles.

In an installation as described in the OP we typically shoot an "L" bracket with a Caddy WMX-6 attached.
 
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