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#52687 - 06/02/05 10:47 PM Floor Duct  
golf junkie  Offline
Joined: Apr 2001
Posts: 507
York, NE
I'm looking at a job that will require a remodel installation of some floor duct. I've never worked with this stuff.

Any pros or cons with flushduct -vs- trenchduct. Which is easier to work with?


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#52688 - 06/04/05 11:16 PM Re: Floor Duct  
Scott35  Offline

Broom Pusher and
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
There are several Manufacturered types of Floor Duct / Infloor Raceway - each have Pros and Cons.

The type I am most familiar with is "Walkerduct" - from, of course, Walker / Wiremold.

The (most common) Walkerduct systems consist of:


[*] 1 Electrical Duct - dimensions being apx. 2.25" H x 4.25" W,

[*] 1 Communications Duct - dimensions being apx. 2.25" H x 6.75" W,

[*] Junction / Pull boxes W/ 12", 14" or 18" round covers - sized depending on type and number of Ducts used + necessary Volume,

[*] Couplings for Ducts,

[*] End Caps - come in two flavors: Cherry and Vanilla [Linked Image]...
No, actually the two flavors are "Dead-End Caps", where the Duct simply ends, and "Riser-End Caps", where a Riser section of Duct is used to connect to a Panelboard - or stub flush with the floor at a T.B.B. (there are also ends with K.O.s for connection to Conduit),

[*] Activation Boxes: these mount at finished floor level, via long, threaded Nipples - which screw into the Factory installed (or field installed) Threaded Hubs of the Duct.
Boxes come in many types.

The Ducts are 10' lengths, with options for factory mounted access hubs @ either 12" centers or 24" centers (have used more 24"C than 12"C), or simply "Blank" Ducts (no Hubs).
There are also "Inserts", which allow placement of a Hub at any point on the Duct - or to cut in a Hub on "Blank" Ducts.

Infloor Raceways are actually kind of interesting and a "Good" challenge to install. You should not have any problems with the installations, just "Out Think The Materials!"

Place the Ducts, so the top of the Hubs is just about ΒΌ" below the flush / "soon to be" finished floor. Do the same with the Junction / Pull boxes.

Under the Junction / Pull boxes + intervals of the Duct (like at couplings), "Grout-In" these items with Concrete after they are set flush.
This eliminates the problems of having voids in the Concrete when Trenches get filled, eliminates the problems resulting from People / Things standing on the Ducts and causing damage (during the time the Trenches are still open), and also keeps the entire assembly sturdy during the Concrete fill process.

Don't perform any make-up in the Duct!
Pull from J-Box to Outlet, and do make-up in the J-Box.

Lastly, if you will be involved in the Concrete finishing of the Trenches, make it easy to find and knock out the covers over the Hubs you will be activating. After the Carpet is layed out, then you will return to install the Outlets, so do something to identify the access points, and inform the Carpet Installers - so they will make cuts at these points.

Make sure the finished level of the Concrete is nice and uniform around the activation points too! Too low at the centers, and the Nipples will not reach the Hub. Too high at the centers, and the Outlet will not seat completely to the floor.

I forgot to mention some alternatives:

  • Underfloor Raceways: used on Multifloor Buildings, where the floors are Light-Weight types (like "Elastocrete"),
  • Modular Floor Boxes: Used in "Standard" Concrete Floors, these are simply Cast Iron or PVC Outlet Boxes, and connect with Conduit. Some have an option, similar to the "Poke-Thru" Box, described below,
  • "Poke-Thru" Boxes: Used on same types of Floors as listed in the first example above, these require drilling a given size hole in the floor, then "Poking" the assembly thru the floor, until the top is flush with the finished floor. They are secured by tightening up wedging expansions.
    Conduit/Conductor termination is done underneath the assembly.

Good luck.


edited for pour spelleeng!

[This message has been edited by Scott35 (edited 06-04-2005).]

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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