Running electrical through floor
#1
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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.
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.
#2
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?
MC cable is not approved for installation where it is subject to damage. Enclosing everything in electrical raceway, or conduit, would also work.
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The best way is to install a floor box - one that does both power and data
Does "subject to damage" essentially mean out in the open?
What type of conduit would you recommend?
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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.
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.
#5
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.
#6
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?
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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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
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
#8
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.
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.
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.
Also can I pull romex 12/2 through it or would it be better to get THHN?
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.
#9
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
http://www.carlonsales.com/Floor%20Boxes_2B38.pdf
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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).
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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
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
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
http://www.carlonsales.com/Floor%20Boxes_2B38.pdf
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).
#12
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
Safety v. aesthetics
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.

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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.
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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?
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
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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?
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.
#16
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.