knockout seal for odd-shaped hole in metal box

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  #1  
Old 05-14-13, 05:43 PM
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knockout seal for odd-shaped hole in metal box

I have a couple of older style metal boxes installed in the basement with odd-shaped holes on the sides but round holes on the top and bottom. The side holes are kind of oval with a flat bottom.

The problem is that even though the side holes aren't being used right now, they are punched out because they were in use at one time. They are mostly covered by older style metal clamps from inside the box, but this doesn't seem to totally do the job well. I have a "certificate of occupancy" inspection coming up and don't know how detailed they'll be so I want to make sure all holes are fully covered. Is there a knockout seal that is made for this special shape? I've only seen round ones.
 
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Old 05-14-13, 05:51 PM
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How would anyone know what the hole looks like your drying to fill without a picture?
A step drill can be used to make the hole nice and round again so a standard plug will fit.
 
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Old 05-14-13, 05:52 PM
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Is it possible to shoot a picture and post it here for us ?
 
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Old 05-14-13, 06:46 PM
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Sounds like the OP is asking about the KO's for a cable in a metal box with the internal clamps. They are kind of D shaped.

I don't think they could be drilled out for a standard KO seal due to the location in the box. I have never seen a KO seal for them either.
 
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Old 05-14-13, 06:58 PM
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Good call Boss. Sounds about right.

Usually if you use NM clamps inside the box and tighten them down the holes are pretty much covered.

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  #6  
Old 05-14-13, 07:00 PM
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Yep, pcboss has it right. They are kind of d-shaped holes.....old boxes with internal clamps that you screw down. If I get time I will try to post a photo, but it won't be tonight.

I'll check into drilling the holes with a step drill (great idea!), but they might be spaced too close together on this box.
 
  #7  
Old 05-14-13, 09:45 PM
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I'll check into drilling the holes with a step drill (great idea!)
Um, no, not exactly.
they might be spaced too close together on this box.
Not only that, they should be tight against the back - or bottom - of the box. Put a step drill in that and you'd better have the replacement box on the job.

If the internal clamps are still in the boxes, I've passed inspection for years (never failed) by just tightening the clamps down to seal the openings. If they're missing, steal them from any spot in any box where neither of the KOs was ever removed. Steal one out of a new box if you have to - faster, cheaper and less likely to create a problem than replacing the box.

I wasn't hiding anything on those inspections, either. I've actually talked about it with the inspectors, and they're good with it.
 
  #8  
Old 05-15-13, 05:28 AM
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Nashkat1, after looking closer at the box, you're right that the step drill maneuver is a bad idea here. I'll just tighten the clamps as you and PJmax suggest. Thanks for the help, everyone!
 
  #9  
Old 05-15-13, 09:06 AM
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Thanks for the feedback.

My apologies to PJmax - I missed that you'd already talked about just tightening the clamps down. I would have quoted you instead of typing the whole thing over again if I'd caught it!
 
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Old 05-15-13, 11:20 PM
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No problem.....we'll call it server lag. Yeah...that's it.....server lag.
 
  #11  
Old 05-16-13, 07:41 AM
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Would it be code compliant to simply cover the holes with metal tape like is used for HVAC ductwork?
 
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Old 05-16-13, 08:37 AM
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Would it be code compliant to simply cover the holes with metal tape like is used for HVAC ductwork?
No .
 
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