Securing ENT in a Steel Truss Ceiling?

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JFletcher

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I'm working on a project right now where I need to secure numerous drops of 3/4" ENT for comm cables inside of a steel truss ceiling. These trusses span approx 60' across a hotel lobby and breakfast area. Screwing in anchors to the floor above for superstrut is out of the question, as its only plywood above the trusses - wouldnt want anchor bolts sticking up into the guests' feet in the rooms above. =D

Anyway, this is the first time I have run across this construction method and would appreciate any links to products designed to attach conduit to these trusses. Didnt see what I needed on T&B/Carlon site.

Not sure I am describing them correctly, but they look like 4 pieces of angle iron connected together with rebar that forms interlocking triangles.

Only thing I have come up with would be field fabrication/cutting of lumber that could sit in between the trusses as anchor points. There has to be a better way. Any input appreciated.
 
Is zip-tying the tubing to the metal framing out of the question? I've done it like that in a suspended ceiling application where it would be hidden from sight. I don't exactly know what you have going on there.
 
Thank you gentlemen.

Jay: that was my initial thought, and I dont see anything in 362.12 or 362.30 (or elsewhere) that would prohibit zip-tying ENT to steel trusses. Just didnt seem right tho.

The trusses look a bit like this: http://www.aecinfo.com/1/resourcefile/00/32/63/tr06a.jpg

I hope that helps visualized the installation.

Jim W: It's above a fire rated ceiling, but that space is not an air return, so I wont need plenum-gard or CMP cable. The conduits will run both perpendicular (through the trusses) as well as parallel. Any strut would need to be attached to the trusses.
 
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JFletcher said:
These trusses span approx 60' across a hotel lobby and breakfast area.
Click to expand...

ENT is like a wet noodle - unless supported A LOT it looks like hose... :roll:

Anyway - I assume is only com/data cable? You may want to check the listing of the floor above the ceiling.

362.10 Uses Permitted.
​
​
(5) Above suspended ceilings where the suspended
ceilings provide a thermal barrier of material that has
at least a 15-minute finish rating as identified in
listings of fire-rated assemblies, except as permitted in​
362.10(1)(a).
Click to expand...

362.12 Uses Not Permitted.
(8) In theaters and similar locations, except as provided in​

518.4 and 520.5
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518.4
​
​
(C) Spaces with Finish Rating. Electrical nonmetallic
tubing and rigid nonmetallic conduit shall be permitted to
be installed in club rooms, conference and meeting rooms
in hotels or motels, courtrooms, dining facilities,
restaurants, mortuary chapels, museums, libraries, and
places of religious worship where the following apply:
(1) The electrical nonmetallic tubing or rigid nonmetallic
conduit is installed concealed within walls, floors, and
ceilings where the walls, floors, and ceilings provide a
thermal barrier of material that has at least a 15-minute
finish rating as identified in listings of fire-rated
assemblies.
(2) The electrical nonmetallic tubing or rigid nonmetallic
conduit is installed above suspended ceilings where the
suspended ceilings provide a thermal barrier of
material that has at least a 15-minute finish rating as
identified in listings of fire-rated assemblies.
Electrical nomnetallic tubing and rigid nonmetallic
conduit are not recognized for use in other space used for
environmental air in accordance with 300.22(C).
FPN: A finish rating is established for assemblies
containing combustible (wood) supports. The finish rating
is defined as the time at which the wood stud or wood joist
reaches an average temperature rise of 121?C (250?F) or an
individual temperature rise of 163?C (325?F) as measured
on the plane of the wood nearest the fire. A finish rating is​

not intended to represent a rating for a membrane ceiling.
Click to expand...

That said - zip ties... Tie wire...
 
JFletcher said:
Thank you gentlemen.

Jay: that was my initial thought, and I dont see anything in 362.12 or 362.30 (or elsewhere) that would prohibit zip-tying ENT to steel trusses. Just didnt seem right tho.
Click to expand...

I snuggled 3/4" into one of the 4 angle pieces. Ran it along the truss until I needed to change direction. Then I'd run it through the triangle "holes" and tie it to same side of each triangle when running crosswise.

Just make sure it is supported at the proper intervals and don't put even 270 degrees of bends without breaking up the run with a junction box. Unlike EMT and PVC, the tubing doesn't tend to hold strong as you're trying to force the cable through the raceway.
 
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