Running electrical through floor

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  #1  
Old 07-25-12, 08:28 PM
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Running electrical through floor

I have a computer desk with a 2 computers on it in the middle of my office. There are all sorts of wires running all over the place and I am trying to clean it up. Under the office is an unfinished basement. I plan on putting the computers down there and running everything through a hole in the floor.

Most of the logistics I have sorted out (usb, monitor cable, etc). I will need some power top-side for the monitors and speakers. I was initially thinking of just having an extension cord run through the hole, but that would require a fairly big hole.

Then I figured I could just run romex to keep the hole fairly small, but this probably wouldn't be the smartest idea and I know it would be against code.

I looked at lowes to try to get some ideas, and came away with this:
Shop 25-ft 12/2 MC Cable at Lowes.com

(it's going on a 20 amp circuit). But is this really the best way to go? Can I run this through the floor and tie wrap it to a leg of the desk, then route it in to the innards of the desk where I will have an outlet.

There were a lot of choices at lowes and I didn't really know what the best route would be. Non-metalic condiut that I can run straight romex through (or thhn wire?) Also keep in mind there will be other cables running very near by, such as the video signal, so electrical interference could play a part.

I need it to be a little bit flexible, but most importantly want to keep it safe. What is the proper way to do this?

Any tips would be appreciated.
 
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  #2  
Old 07-25-12, 08:54 PM
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I need it to be a little bit flexible, but most importantly want to keep it safe. What is the proper way to do this?
The best way is to install a floor box - one that does both power and data. Example: Hubbell Floor Boxes.

MC cable is not approved for installation where it is subject to damage. Enclosing everything in electrical raceway, or conduit, would also work.
 
  #3  
Old 07-25-12, 09:10 PM
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The best way is to install a floor box - one that does both power and data
I thought about that, but one of the main reasons I am doing this is to baby proof the room. If I have electrical plugs coming out of the floor, easy for the kid to mess with them.

Does "subject to damage" essentially mean out in the open?

What type of conduit would you recommend?
 
  #4  
Old 07-25-12, 11:24 PM
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I think the floor box is still the cleanest option. If you get a recessed box with cable doors then you can still make all of the connections in the box and close the lid. Only the cables would emerge from the floor. If you need to secure the box cover, you could probably drill and tap a screw through the cover into the flange of the box.

If you are set on conduit, you will want to run the data wires in a separate conduit from the power lines. Also, if you put the power lines in metal conduit (emt or flex) you will provide a shield for EMI coming from the power lines. At the desk, if the power lines have to cross the signal lines, it is preferred that they cross perpendicular to each other. Much of this is not as important if you are using good quality shielded data cabes.

Run the conduit up the desk leg to a box and secure the wires to provide some degree of strain relief. If you want to minimize the hole size, go with THHN conductors over Romex. The conduit isn't supposed to be filled more than 40% and Romex may require you to go to a larger conduit size than THHN. Remember that where the wire emerges from the conduit should have some sort of insulating bushing or clamp to prevent the wire insulation from being pierced by the sharp edge of the conduit.
 
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Old 07-26-12, 04:02 AM
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In addition to the other comments, any hole between floors must be fire blocked using an approved material (caulk). Just having a hole in the floor won't be safe.
 
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Old 07-26-12, 09:36 AM
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one of the main reasons I am doing this is to baby proof the room. If I have electrical plugs coming out of the floor, easy for the kid to mess with them.
As Sparky31415 noted, a recessed box with cable doors puts the electrical plugs and data connections out of reach. Many of the covers are essentially baby-proof too, as they latch closed and require some mechanical action to release the latch. If you scroll down the page at Hubbell Floor Boxes, you can see all the different boxes, inserts and covers - and Hubbell is only one manufacturer. You might want to visit an electrical supplier with a showroom where you can get your hands on some of the options.

Does "subject to damage" essentially mean out in the open?
Yes. Without protection. Not installed within a structure nor a raceway (which may be a conduit).

What type of conduit would you recommend?
Running conduit through the floor is not recommended, in part for the fire safety reasons Chandler noted and the need to effectively address those. Cord bundling above the floor box can be accomplished more easily with braided cable sleeving.

That said, if you still want to install some exposed conduit - to connect to a box mounted in or on the surface of the desk, for example - then non-metallic liquidtight might work well for this application.
 
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Old 07-26-12, 12:06 PM
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That said, if you still want to install some exposed conduit - to connect to a box mounted in or on the surface of the desk, for example - then non-metallic liquidtight might work well for this application
I am still leaning toward the exposed conduit option, I looked seriously at floor boxes... however, I view it as an eyesore in case I end up wanting to move my office, or even my desk. With the conduit option, if I want to remove the whole thing in a few years it will only leave a small hole in my floor.

At any rate, I did see the non-metallic liquidtight at lowes and it looked promising.

With this type of conduit, I couldn't figure out at by looking at the connectors at lowes how to connect it to a steel junction box with a 3/4" KO. The guy at lowes said just use a romex clamp down but that seemed wrong. Some of the conduit had connections already applied, but they were 25 feet or something long and I only need about 6-8 feet.

Also can I pull romex 12/2 through it or would it be better to get THHN? I have some 12/2 romex, so that would save some extra costs. In the research I did, it didn't seem anything in the NEC prohibited pulling romex through it... but it might be difficult?

Thanks again for everyones responses
 
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Old 07-26-12, 01:46 PM
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I am still leaning toward the exposed conduit option, I looked seriously at floor boxes... however, I view it as an eyesore in case I end up wanting to move my office, or even my desk. With the conduit option, if I want to remove the whole thing in a few years it will only leave a small hole in my floor.
How baby-safe do you want this room to be?

All UL-approved floor boxes are designed, constructed and tested to maintain the fire rating of the floor, so long as they are installed according to their instructions. While it might be possible to do that with a conduit penetration, it would be a bit of a challenge. Certainly with more than one conduit.

Safety v. aesthetics.

I did see the non-metallic liquidtight at lowes and it looked promising.

With this type of conduit, I couldn't figure out at by looking at the connectors at lowes how to connect it to a steel junction box with a 3/4" KO. The guy at lowes said just use a romex clamp down but that seemed wrong.
Non-metallic liquidtight requires connectors made for it. The guy at lowes eas talking through his.. er... head. Check at HD or an electrical supply house. And don't you need 3/4" conduit at least twice, if not three times? 3 x 8 = 24?

Also can I pull romex 12/2 through it or would it be better to get THHN?
THHN. Type NM-B, aka Romex, can be sleeved in conduit for a short distance for protection, but not used as the pull through a complete raceway.

Speaking of that, it seems to me that part of making the floor penetration safe will be to have a complete raceway - conduit ending in an approved box on each end.
 
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Old 07-26-12, 06:37 PM
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Here is another floor box that may be a little more cost effective for installation in a residential wood floor. Look at pages 2-3 and 5-6.

http://www.carlonsales.com/Floor%20Boxes_2B38.pdf
 
  #10  
Old 07-26-12, 06:57 PM
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Ideas for you

Consider reducing the number of wires by using a switch or even a power-over-ethernet. You can always bundle your computer wires using some zip ties. The best ethernet cable will be either Cat6 or Shielded Cat6(requires grounding if i remember right).
 
  #11  
Old 07-26-12, 08:09 PM
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How baby-safe do you want this room to be?

All UL-approved floor boxes are designed, constructed and tested to maintain the fire rating of the floor, so long as they are installed according to their instructions. While it might be possible to do that with a conduit penetration, it would be a bit of a challenge. Certainly with more than one conduit.

Safety v. aesthetics
I wanted to make this pretty simple, and I think a conduit is more simple then a floor box. Also I think it is more baby proof, unless my kid gnaws thru the conduit! I know a floor box could easily be baby proof but those that have a cover on them don't look great. I want to be able to take this whole thing apart if I move my office.

Here is another floor box that may be a little more cost effective for installation in a residential wood floor. Look at pages 2-3 and 5-6.

http://www.carlonsales.com/Floor%20Boxes_2B38.pdf
These are great if one was going the floor box route. Still, I don't want a plug just sticking out of the floor where I kid could come over and start messing with it.

Consider reducing the number of wires by using a switch or even a power-over-ethernet. You can always bundle your computer wires using some zip ties. The best ethernet cable will be either Cat6 or Shielded Cat6(requires grounding if i remember right).
I've looked in to that stuff, but I shouldn't have too many wires. The big ones are the DVI connectors. 2 of those, 2 x usb, 2 x audio (those are small) and 1 ethernet cable. I know I can try to cut down on the DVI by using HDMI, that saves a little...
 
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Old 07-26-12, 10:30 PM
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Originally Posted by Nashkat1
All UL-approved floor boxes are designed, constructed and tested to maintain the fire rating of the floor, so long as they are installed according to their instructions. While it might be possible to do that with a conduit penetration, it would be a bit of a challenge. Certainly with more than one conduit.

Safety v. aesthetics
I wanted to make this pretty simple, and I think a conduit is more simple then a floor box. Also I think it is more baby proof, unless my kid gnaws thru the conduit!
I don't think you heard me. Perhaps I wasn't as clear as I was hoping to be. I'll try again.

1 - A UL-approved floor box is rated to stop the spread of a fire between floors at least as effectively as the floor would if no box were installed.

2 - Cutting a hole in a floor and running a conduit through it may serve as a pathway for a fire to be spread between floors. There is no UL rating for that because it depends on how you do it.

Your kid gnawing through the conduit is not the issue here. Preventing the spread of a fire is. It doesn't matter how damage-proof the conduit itself is if it aids in the spread of a fire. How safe is that for your baby, you, and the rest of your family?

I know a floor box could easily be baby proof but those that have a cover on them don't look great. I want to be able to take this whole thing apart if I move my office.
It sounds like you're more concerned about how it looks than about doing it safely.
 
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Old 07-27-12, 09:14 AM
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2 - Cutting a hole in a floor and running a conduit through it may serve as a pathway for a fire to be spread between floors. There is no UL rating for that because it depends on how you do it.
When they built my house (2001) they routed BX cable through a hole in the floor for the oven, range, and dishwasher. It passed inspection I assume.
 
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Old 07-29-12, 03:33 PM
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What do you need two computers for?

How about stepping back a moment - what do you need to do with those two computers and how? Do you need direct physical access, such as for pin-outs/hardware projects: Do you need high performance such as for FPS gaming?

How about the possibility of a home wireless network? I have computers, remote hard drives, and a printer in my basement, and I can use my laptop over the wireless network to use them all, through Remote Desktop/VNC/X/SSH/CIFS/NFS. If all you need is a screen, keyboard and mouse, a laptop, tablet or thin client over wireless network might be an idea. You'd be left with one or zero cords. Who needs the hole in the floor?
 

Last edited by wgc; 07-29-12 at 03:34 PM. Reason: making the point explicit
  #15  
Old 08-01-12, 08:33 PM
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How about stepping back a moment - what do you need to do with those two computers and how? Do you need direct physical access, such as for pin-outs/hardware projects: Do you need high performance such as for FPS gaming?
Yes one of them is a high performance computer, the other is a mid-range computer. Before I started this project, both computers sat on the floor of my office with a bundle of wires around them including surge protectors, power cords, etc. If my baby got within 5 feet of the whole thing I would usher him away. It got to the point basically where he couldn't come in to my office as within a minute or two I would have to stop him from getting in to the mess of wires.

My idea was to put the computers in the basement (on a shelf near the ceiling) and route the cables through a hole or two in the floor. Initially I was thinking of running on extension cord through the floor but as I thought about it, I figured a conduit would require a much smaller hole.

The two computers in the basement work great. Less noise, they run cooler, and I don't have to worry about my kid getting electrocuted.

I have two holes in my floor, one 1/2 inch (for the MC flex cable) and the other about an inch for the monitor cables, speaker cables, and USB.

I have a home network with ethernet in every room but I need real computers in my office, not a laptop over a wi-fi network.
 
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Old 08-01-12, 09:44 PM
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I have two holes in my floor, one 1/2 inch (for the MC flex cable) and the other about an inch for the monitor cables, speaker cables, and USB.
No floor penetration using electrical or data cables without adequate physical protection and fire prevention methods meets current code requirements.
 
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