Lamp in Middle of Room (Need Power Supply)

Discussion in 'Electrical Forum discussion & Blog' started by molo, Apr 19, 2012.

  1. molo

    molo Member

    Messages:
    844
    Location:
    cold new york
    Hello,

    Details:

    House is on Slab with carpet and a plywood sub-floor. The plywood sub-floor has a rigid plastic drainage mat attached to the bottom. Open living room with no partition walls for power. Home has a minimalist design that would be disturbed by the addition of a wall or column that serves as a chase for power.

    Problem:


    There is a floor lamp placed in the middle of the living room. The home-owner wants to avoid having the extension cord run over the floor.

    Question:

    How can he get power to the lamp?



    Thanks,
    Bill
    Last edited: Apr 19, 2012
  2. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    996
    Location:
    NY State, USA
    Cut the floor. It's the only way.
    Unless of course they will accept a drop from the ceiling. :p
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    Use batteries .
  4. Chad Schloss

    Chad Schloss Member

    Messages:
    329
    Location:
    USA
  5. molo

    molo Member

    Messages:
    844
    Location:
    cold new york
    Would the concrete have to be cut or the 5/8"plywood subfloor with 1/2" rigid drainage board on bottom?

    Wondering what type of wire and if an outlet box on the floor would be necessary.

    Batteries are sounding better!

    Thanks!
  6. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Cutting the concrete would 1) be a pain. 2) technically the best way.

    I wonder. Pull back the carpet. Cut the ply subfloor say 2' wide. Cut the drainage board 1" wide centered on the 2' of the plywood. Use NM intended for direct burial in the ground, as that is unconcerned about how damp the concrete might get. Conventional NM is rated for damp. Certainly not for wet. The direct burial stuff will cost about twice as much. Well worth the upgrade under the circumstances.

    In open office arrangements on slabs classically the power for the various desks would come up in a "monument" which is typically a cast aluminum affair that houses an outlet above grade. It could be legitimately secured to the ply and as long as one had a suitable strain relief for the NM, you would be legit.

    Assuming that you are running a 15 amp circuit, you need a box with a minimum of 10 cubic inches. 2x each wire, and 2x2 per strap. Can you find a box that is 1 1/8 or 1 1/4" deep, with a volume of 10 cubic inches? Possibly then you could install the outlet on its back. 4x4 boxes that are 1 1/2" deep can be had all day. There is also a plastic box that allows for one strap (an outlet in your case) that has space to one side that increases its capacity. I know it is very shallow and that it has enough capacity for you, but I don't know the manufacturer. Home despot at least, stocks it for you.

    The architect dropped the ball on this one, as he should have specified one or two flush in the floor boxes for outlets. Now you would need to bore a hole in the concrete to install one, even if you did feed it with NM above the slab.

    Possibly search around for an image of a monument and show it to the customer, see if they bite.
    Last edited: Apr 23, 2012
  7. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Carlon box

    Oh, of course. Carlon.

    This box is only 8 cubic inches, but it is 1 1/4" deep: B108R-UPC

    The one I was thinking of that has a space off to the side to increase its capacity is an old work box and is 2" deep.

    I'd use the 1 1/4" deep box with a nice bronze cover, all facing up, and call it good.
  8. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Huh. Low voltage. Not the worst idea by half. I wonder how many lumens one can get down that stuff without melting it? Recognizing that it will be living under the carpet.....
  9. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Or use Wiremold (registered)

    Or you could work in wiremold. Don't know how it would last strapped down to a concrete slab. Possibly 50 years..... But the boxes are 1" deep, with enough capacity, I am sure. And your thwn would be in a metal raceway that would be difficult to breach. The raceway comes in two depths the shallower of the two would be .53", so that would fit under the ply.
  10. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    This bell box is supposedly 1 1/8" deep, and has plenty of room:

    Taymac 1-Gang 5-Hole Round Electrical Box

    Model # PRB57550WH

    Internet # 202284522
    Write a review
    Write the first review

    $7.76 /EA-Each

    At home despot.
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    At least he did not consider an extension cord "under" the carpet. Your "bell box" link took me to a description of a "door bell box" for an anounciator type application. I would not run NM wire "exposed" under the subfloor, even if there was little possibility of anyone ever using nails or staples in the wood.
    Last edited: Apr 24, 2012
  12. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Yes, NM under the ply would be dubious. Wiremold would be pretty good stuff. If the underlayment stuff is literally 1/2" it would rule out 1/2" emt, which of course is nearly 3/4" in diameter. The NM could be run in the wiremold. There would need to be some consideration of anti-chafe at each end, but a good connector at the box would satisfy the need for a strain relief at the box. Staple it to some framing soon after it exits the wiremold and enters the wall, and that is your other strain relief.

    The Bell box I referenced is one of those swell cast aluminum items one would use to support exterior lights. Specifically this thing is 4 1/4" in diameter and has threaded holes to take connectors. I know that wiremold has a coupling specifically to transition to conduit in some way or other, quite directly, but I have not worked with it.

    Grainger has photos of it.

    Anyway, a cast aluminum bell box screwed down to the concrete with a bronze face plate will assuredly make a solid and legitimate box to mount an outlet in. Hell, one could daisy chain and put in two, the box is plenty big enough for a line in and a line out.

    The one element that may be an issue is that if the flooring under the carpet is literally 1 1/8" thick, then the box needs to rise up above that to the top edge of the carpet, or nearly. Certainly the carpet cannot be exposed to the interior of the box. And one does not want the bronze face plate to crush down the carpet noticeably.

    The box could be shimmed up. Or a round face plate could close it and support the receptacle, for preference raising it about the thickness of the carpet and pad, like a mud ring. I like the mud ring idea. Get a mud ring with a suitable lift, one for a 4 11/16ths box, and bore a few holes in it such that you can screw it to the bell box. I cannot imagine why an inspector would flag it.

    Or use the wire mold box with a conventional mudring of sufficient offset to lift the face of the outlet to the top surface of the carpet.

    It is like an erector set: there are countless ways of getting there. And some of them are actually legitimate!
    Last edited: Apr 24, 2012
  13. andrew79

    andrew79 Licensed Electrician

    Messages:
    18
    Location:
    Ontario Canada
    if your looking for mechanical protection why not pull individual wires and put a 3/8's conduit under the floor to the location, toss a jb on the other end and run romex to wherever you need to go or use an emt to flex connector and run the individual wire right to your connection point.
  14. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Well, if you are looking at 3/8ths (which is a good idea) why not just use metal clad? Either way, is this a damp location?

    Keeping in mind how shallow the box holding the receptacle needs to be to end up flush with the top side of the carpet.
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