Wiring in insulated concret forms (ICF's)

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ammklq143

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Iowa
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Electrician
I have two questions about wiring in an ICF basement.

1. How do you fasten the NM cable within 12 inches of the box, or don't you, since it runs in a groove cut in the ICF?

2. Since I am using 4 inch metal boxes with mudrings, do I need a ground conductor connected to the box/mudring?

Thanks.
 
Ive done that before, its a real pain. I assume the rock is going right on the foam and its not getting studded out? Are you chewing away the foam and tapconing a box right to the concrete? There is no actual exception I see to the securing requirement so I would run it by the inspector and see if he cares. If he does perhaps you could zip tie to the nearest poly tie? Yes you need to ground the box. I you are mounting the box right to the concrete I would recommend getting boxes that have the recessed ground screw hole.
 
ammklq143 said:
I have two questions about wiring in an ICF basement.

1. How do you fasten the NM cable within 12 inches of the box, or don't you, since it runs in a groove cut in the ICF?

2. Since I am using 4 inch metal boxes with mudrings, do I need a ground conductor connected to the box/mudring?

Thanks.
Click to expand...
1. I use a zip tie that has the eye on the end and the same kind of concrete anchor that I use to mount the box.

2. Anywhere that an EGC comes into a metal box and is spliced you have to bond to the box. You may not need to attach an EGC to the device. Switches- no. Recepts- depends, some have the grounding tab on one of the screws.
 
Why would you not be able to secure and support the NM within the channel you cut by spraying some foam around it? That would seem to cover it quite nciely.
 
Thanks for the help. I did call the inspector and he said I could cut a groove in the ICF for the conductor and use expanding spray foam to hold it in. He said he wouldn't make me actually strap it, as long as it was set back in the foam 1 1/4 inches and held there with something.

My supplier did send me boxes with the raised ground screw hole. Thanks for the suggestion. I'll have to make sure to specify those next time, just in case.

Thanks again.
 
Oscillating tool works great for cutting the foam forms. Hot knife works even better, but you won't use it for anything else. Wedge just about anything you can find that will not damage cable into your groove to hold it in place or use expanding foam as others have mentioned.
 
ammklq143 said:
Thanks for the help. I did call the inspector and he said I could cut a groove in the ICF for the conductor and use expanding spray foam to hold it in. He said he wouldn't make me actually strap it, as long as it was set back in the foam 1 1/4 inches and held there with something.
Click to expand...

The 1.25" setback is required from the front edge of framing members not from the back surface of the Sheetrock.
 
infinity said:
The 1.25" setback is required from the front edge of framing members not from the back surface of the Sheetrock.
Click to expand...


I'm not sure I understand what you mean. Wouldn't the back surface of the sheetrock and the front edge of the framing members (ICF form) be the same thing. They screw the sheetrock directly to the ICF, so it would have to be set in 1 1/4 from the front edge of the ICF or the back of the sheetrock, right?
 
infinity said:
The 1.25" setback is required from the front edge of framing members not from the back surface of the Sheetrock.
Click to expand...

ammklq143 said:
I'm not sure I understand what you mean. Wouldn't the back surface of the sheetrock and the front edge of the framing members (ICF form) be the same thing. They screw the sheetrock directly to the ICF, so it would have to be set in 1 1/4 from the front edge of the ICF or the back of the sheetrock, right?
Click to expand...

I suppose you could consider the plastic ties of the ICF as being the framing members and you will need to be 1-1/4 back from those. Not really any different concept than if you had wood furring strips on a concrete wall that gets a wallboard applied over it.
 
The ICF stuff that we encountered had plastic "studs" spaced every 16 inches for the attachment of drywall. They were not always apparent. You could take a nail or awl and poke into it to find these "studs" -- keep your romex away from that area in any case.

We simply cut a groove into the styrofoam and tucked the wires in there, with some expanding foam to keep it in place.
 
ammklq143 said:
I'm not sure I understand what you mean. Wouldn't the back surface of the sheetrock and the front edge of the framing members (ICF form) be the same thing. They screw the sheetrock directly to the ICF, so it would have to be set in 1 1/4 from the front edge of the ICF or the back of the sheetrock, right?
Click to expand...

The 1.25" setback would only apply to the member that the Sheetrock gets fastened to. You could run in a shallow groove down the center of the ICF just deep enough to fit the cable in. Maybe someone could post a photo f an ICF installation.
 
In the YouTube link I posted above, at the end it shows installation of the cable and boxes using a hot knife.
 
electrofelon said:
Ive done that before, its a real pain. I assume the rock is going right on the foam and its not getting studded out? Are you chewing away the foam and tapconing a box right to the concrete? There is no actual exception I see to the securing requirement so I would run it by the inspector and see if he cares. If he does perhaps you could zip tie to the nearest poly tie? Yes you need to ground the box. I you are mounting the box right to the concrete I would recommend getting boxes that have the recessed ground screw hole.
Click to expand...


I bought some ground straps for the boxes. They come with a screw in one end and a forked terminal on the other end. Should I clip the fork terminal off and tie the ground strap in with the ground conductors, or does it terminate with the fork terminal somewhere?
 
ammklq143 said:
I bought some ground straps for the boxes. They come with a screw in one end and a forked terminal on the other end. Should I clip the fork terminal off and tie the ground strap in with the ground conductors, or does it terminate with the fork terminal somewhere?
Click to expand...

If you buy the right ones you will have two or three lengths of green conductor all terminated together at the screw, one (or two for 2 gang applications) will have fork terminal(s) for attaching to devices and the other lead has no connector on it and is for wirenutting with other grounding conductors.

If you just have a single conductor with screw on one end and fork on the other, it must be intended to go from box to device - not the best one to use for wiring methods that include a equipment grounding conductor vs using a raceway as the EGC but it will work. The idea is to save some time on installation. If you have to modify the pigtail you are not getting full benefit of time saving you would get if you have the right one for the application.
 
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