How to install floor receptacles?


  #1  
Old 11-01-04, 10:58 AM
LowellSpecht
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How to install floor receptacles?

I want to install 3 floor receptacles in my wood shop. The shop has a wooden floor on cinder block piers. I can access the floor from underneath. I plan to install hardwood flooring over the subfloor at some point in the future. Total thickness of the flooring (subfloor plus hardwood) will be 1.5 inches. I have a 100 amp service panel in my wood shop. The electrical work will be inspected.

I've had some trouble finding an electrical box for the outlets that suits my needs. It may be that I don't know what to look for. I'm assuming the boxes need to be weather proof and the cable needs to be rated outdoor and in conduit. What kind of boxes should I use and how should they be installed? One of the outlets will be 240 volt and the other two will be 110 volt.

The books I have don't address this type of installation specifically. I'm not sure if the boxes need to be flush with the upper floor surface or if they can be recessed from the floor surface. The weather proof PVC style boxes I can find at Lowe's and Home Depot don't appear to be designed for this application or I just don't know how to use them. Please advise.
 
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Old 11-01-04, 11:31 AM
G
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H.D. and others have a floor mounted recept. but its only for 110 V and quite expensive. It has a brass faceplate and a screw in plug to protect it when not in use.

I would rethink my needs vs wants and maybe consider some form of pedastal mounting, where the plugs are off the floorand less likely to get wood dust or accidential water spillage into them.

Stay tuned, I'm sure others will have further on this.
 
  #3  
Old 11-01-04, 11:42 PM
Savant
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As mentioned, floor mount stuff will be costly, and there may be other considerations if your floor is considered an 'external' area. (as you mention weatherproofing)

The only floor stuff I have worked with is made by Wiremold for commerical applications. Here's an example of what they have for wood floors. You just run cable between them. (if you click the link, look to the left on that page for the 'cutsheet' PDF which has info on related boxes and covers)

The only issue would be whether your underfloor area is considered 'external' or 'crawl space'. More info on your setup would likely be handy in this case.

Regards,

Savant
 
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Old 11-02-04, 05:48 PM
LowellSpecht
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I prefer not to have the outlets above floor level on pedestals but may end up having to do that. Unfortunately, I don't think the area underneath the shop can be classified as a crawlspace. In my opinion it is an external area. Only Lattice was used to hide the concrete piers (and anything else under the shop) from view.

I think I can easily handle the weather with PVC conduit but couldn't really find an electrical box that would take the conduit and also protrude through 1.5 inches of flooring and be weatherproof. I checked the Walker 861 you recommended but it is not weatherproof.

One idea I had was to build a weather proof compartment below the floor where the outlets would be located, then just run the conduit into the compartments. Access from above would be with a cut out section of floor that could be easily removed. I should mention that all the outlets would be located together in the center of the shop. The access door would also prevent any spillage of dust or liquids into the outlets when in place. Does this sound reasonable?
 
  #5  
Old 11-02-04, 10:29 PM
Savant
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They actually have an underfloor PVC conduit line, as you can examine here. Check out the cutsheet for details, and you'll see they are flush to the floor. The only problem is that they were designed for installation in concrete, and they are not likely rated to be installed in your situation.

If you want to be on the safe side, the ideal situation would be to build in a 6" subfloor and then use the underfloor wood boxes that I linked above. (which do have flush to floor covers) Yeah it's a lot of work, but at least you wouldn't have to concern yourself with being waterproof. Or you could look at a modular floor system that would give you the flexibility to move your outlets in future should you rearrange your shop. Whether you have the ceiling height is another matter of course.

Regards,

Savant
 
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Old 11-04-04, 06:53 PM
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Heres a suggestion: Why not run the conduit to stub-up {about 6" to 8"} thru the floor at the desired location with an aluminum W.P. box. To secure the box {conduit cannot be used as support per NEC} use a peice of unistrut of sufficient length bolted to the floor & attached to the back of the box thru the K.O. with a 1/4-20 bolt & springnut.You'll also need a conduit hanger with a 1/4-20 bolt & springnut to support the pipe. Hope this helps
 
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Old 11-04-04, 06:55 PM
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This method will prevent or limit the amount of damage in the event of a water leak or flood
 
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Old 11-22-04, 06:09 AM
LowellSpecht
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Thanks to all who responded to my post. I decided to call the inspector and run my plan to build the weatherproof compartment and get his input. Glad I did. He said since under the floor was considered to be "under a roof" I didn't need conduit or outdoor cable. Romex would work fine and I wouldn't need to build the weatherproof compartment. So I simply bought some weatherproof PVC outlet boxes and ran the cable to them without conduit. I did decide to use outdoor cable anyway for my own piece of mind. He did say I needed to put the weatherproof covers on the receptacles to prevent sawdust from getting in and I did that. My final inspection passed last week.
 
 

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