Threaded conduit - does it exist?

Old 11-15-02, 07:37 PM
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Threaded conduit - does it exist?

I am planning on putting a GFI outside of my house. I bought a box and cover from Red Dot. I have a couple of questions regarding the mounting of the box.

I will be mounting the box to the outside of the house and running the conduit in to the back of the box. I will be mounting it low enough so that I can bring the conduit out from the top of the basement, up at the rafter level. I've heard this referred to as the "skirt" of the house.

I want to minimize the hole that I need to put through the house. The guy at Home Depot suggested using a set screw connector at the back of the box. Since this connector will be recessed into the hole, I will not be able to screw the connector onto the conduit when it is in place. I would have to cut a short piece of conduit, attach it to the box with the set screw connector, Attach the box to the house and then use a coupling to connect the rest of the conduit to the short piece inside the basement. The thing that I don't like is the set screw connector will force me to make a larger hole than I would like, especially to accommodate the screw.

The instructions that come with the box mentions threaded conduit. Conduit that would screw right into the box without a connector would allow me to make a smaller hole. Does this exist and where would I find it?

I also have a question about the physical mounting of the box. This box does not have a screw tab on the outside like some boxes. What appear to be mounting holes on the inside are covered by metal plates used for mounting the receptacle. There doesn't appear to be any way to mount this to the house. Will the conduit connection alone provide a suitable mounting?

Thanks in advance,
Old 11-15-02, 08:26 PM
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Yes,, ridgid conduit,,, essentially a galvanized steel pipe nipple. Then you can adapt with a coupling and a connector back to emt. There is probably spots marked in the box to poke a screw thru or drill holes to put screws in for mounting. I have on occasion used a set screw connector,, tighten securely and then snip the screw off and just notch the house a bit with a chisel so it fits.
Old 11-16-02, 05:56 PM
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There should be some mounting tabs that screw on to the back of the bell box, then you can screw the tabs to the wall. You can also use romex to come through the back of the box or you can purchase a precut nipple from the store that is already threaded for you. Make sure you get a ridgid coupling for the end that is inside the house.
Hope this helps,
Old 11-16-02, 08:03 PM
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Thanks for the input. I did find a couple of three-hole tabs that came with the box and would probably screw into the back of it.
The problem is that I'm cutting a hole in my vinyl siding to mount the box. Getting access to the tabs would require that I cut larger holes in the siding and I do not want to do this.

I should not have waited until the night before I started to ask this question. I ended up having to do the work before I was able to read the replies.

Here's what I ended up doing:

We have vinyl siding over 1" Dowguard foam. I cut a hole in the siding and foam the size of the box so the back of it rested on the sheathing. This worked well for recessing the fixture. The foam provides a snug fit and should prevent the box from rotating.
I used a set screw connector after all. I drilled a hole large enough to accept it (15/16" I think, the connector is 1/2"). Then I notched the hole with a Sawzall to accommodate the screw (I didn't break it off).

Before inserting the box I attached a short piece of conduit. I made the conduit short enough so that the coupling fits tight against the inside of the wall, preventing the box from pulling out. I had to put a washer between the coupling and the wall since the hole was larger than the coupling.

After reading your suggestions, I looked at the box. In the back of it are four recessed circles where the metal is thinner than the rest of the box. I should be able to get a couple of screws through these. No sense in relying on foam and a coupling for mechanical support if I can use a couple of screws.

Thanks again,
Old 11-18-02, 03:17 AM
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Originally posted by HomeownerJ

After reading your suggestions, I looked at the box. In the back of it are four recessed circles where the metal is thinner than the rest of the box. I should be able to get a couple of screws through these.
Are you sure those aren't knockouts? If so, it's not a good idea to use them to mount the box. They are designed to break away.
Old 11-18-02, 07:03 AM
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No they're not knockouts. Wouldn't a standard knockout compromise the water tightness of the box? The only access for connections is the three threaded holes in the box, one in back and one on each side. I plugged the side holes with the plugs provided, wrapping pipe thread tape around the plugs before screwing them in.

These holes were maybe 3/16" in diameter. I ended up drilling through them and screwing the box into the sheathing.


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