Supporting Conduits/Box

horsegoer

Senior Member
Location
NJ
Hello. Have unusual situation. Bunch of recessed 2x2's in acoustical ceiling. Ceiling will be at about 12' AFF but the deck is at about 22' AFF. So there is 10' above the hung ceiling. Job is all EMT and conduit MUST be supported from either beams or metal deck above not ceiling structure or supports.

Temp lighting currently shown in pics.

Usually we put a 4" j-box between roughly 4 fixtures( depending on layout) and install a fixtures tail/whip from fixture to the 4" box. Seems like supporting boxes and conduit might be tricky due to only be able to support from bean or metal deck above. Thinking just like the picture shows supporting of other systems( think it's HVAC) is how we will have to support our conduits. Either threaded rod from the deck to strut or to a conduit hanger like in the pic attached. And I think we can support the 4" box right from out threaded rod or on the strut. Any thoughts or potential PIA issues you see ? Thanks a lot
 

Attachments

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Actually that's a very usual situation. The only unusual part is that they called you before the ceiling was installed.

You can do what you say but it would be cheaper to use grid hanger wires like Dave said to support your EMT and boxes. Don't forget hanger wires to support the fixtures while you are up there.

-Hal
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Hello. Have unusual situation. Bunch of recessed 2x2's in acoustical ceiling. Ceiling will be at about 12' AFF but the deck is at about 22' AFF. So there is 10' above the hung ceiling. Job is all EMT and conduit MUST be supported from either beams or metal deck above not ceiling structure or supports.
Sounds like you'll need to support the boxes and EMT from the deck above with threaded rod. Why can't you just use the black iron and pencil rod?
 

horsegoer

Senior Member
Location
NJ
Sounds like you'll need to support the boxes and EMT from the deck above with threaded rod. Why can't you just use the black iron and pencil rod?
port authority job at airport. I was told you can't although the spec doesn't say that. know anyone who has done work there? maybe they'd know for sure. we haven't yet. was told conduit has to be independently supported.

BTW of slab Is already poured above that metal deck what best deck insert to use? I know those blue banger hanger inserts are.good but that's prior to slab being poured.

Sent from my SM-N960U using Tapatalk
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
We always use these, for 3/8" and 1/2" rod the hole is the same size as the rod size.



What airport we have a big job starting soon at LaGuardia.
 

sameguy

Senior Member
Location
New York
Occupation
Master Elec./JW retired
I hear they will lock you up as a terrorist if they see you using powder actuated fasteners.

-Hal
Shoot your wires in, get it approved first and have the GC contact security with you following up with security posting signs and calling security letting them know when you are starting/stopping; they might post a guard.
If not have fun drilling.
 

horsegoer

Senior Member
Location
NJ
Most of us would install grid wires and hang emt from that. Since you said you use fixture whips can you use emt for home runs, set a few boxes in the room and use MC to daisy chain the light fixtures?
MC is not allowed. Only EMT. Grid wire from where? The deck? Why not threaded rod. Again everything must be independently supported from beam or deck. Can't attach anything from ceiling supports.
 

horsegoer

Senior Member
Location
NJ
Actually that's a very usual situation. The only unusual part is that they called you before the ceiling was installed.

You can do what you say but it would be cheaper to use grid hanger wires like Dave said to support your EMT and boxes. Don't forget hanger wires to support the fixtures while you are up there.

-Hal
What's a good type "hanger wire" to use to support the recessed 2x2's. Something like aircraft wire? Thanks.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
LGA. What exactly is that? Expansion anchor? Just drill and insert?
Rod hanger anchor, yes drill hole, bang in, and tighten. I use an impact gun to tighten it literally takes seconds after the hole is drilled to have it fully installed. No one uses hanger wire in NYC especially in a Port Authority building.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
What's a good type "hanger wire" to use to support the recessed 2x2's. Something like aircraft wire? Thanks.

Grid wire from where? The deck? Why not threaded rod. Again everything must be independently supported from beam or deck. Can't attach anything from ceiling supports.
Wow, you've never done a commercial job like this with a hung ceiling? We know you can't attach anything to the ceiling, that's in the code.

You use the same wire the ceiling guys use to hang the T bar grid from the deck or beams, whichever is available. Two for each fixture, at diagonal corners.

What's there is mechanical and plumbing. You don't need that threaded rod and anchors to support your little conduit and boxes. You use hanger wire.

After the ceiling guys are done and you come in to install your fixtures you'll kick yourself when you see how they did it.

-Hal
 
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infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Wow, you've never done a commercial job like this with a hung ceiling? We know you can't attach anything to the ceiling, that's in the code.

You use the same wire the ceiling guys use to hang the T bar grid from the deck or beams, whichever is available. Two for each fixture, at diagonal corners.

What's there is mechanical and plumbing. You don't need that threaded rod and anchors to support your little conduit and boxes. You use hanger wire.

After the ceiling guys are done and you come in to install your fixtures you'll kick yourself when you see how they did it.

-Hal
There is no wire installed for anything on his job. The grid ceiling in NYC is supported by something other than wires, typically pencil rod and black iron.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
So that's a NYC building code requirement? No wire there now because that's all mechanical so you can't necessarily go by that. Probably a good idea to look at the NYC building code or better yet talk to an AHJ to find out what's permissible since neither of us has done work there before. This could be a Port Authority requirement.

-Hal
 
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