How do I open the back of this receptacle box?


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Old 04-14-21, 02:16 PM
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How do I open the back of this receptacle box?

I'm trying to install an outdoor outlet on the other side of the existing outlet pictured below.

I think the box is original from the 1940s. It's was then covered with plaster and paneling (twice), so it would be very difficult to pull the box out.

I can't seem to bust through any of the knockouts in the back of the box. Do they have to be "pushed" from the other side? The don't seem to be threaded and I can't even get a knife in between the box and the punchouts on the side. The marks on the middle one on the back are from me hitting it with a screwdriver and hammer.

I'm hesitant to open a hole any bigger than necessary on the exterior stucco side. Should I try to drill it out?

Thanks
 
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Old 04-14-21, 02:34 PM
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Looks like the box is tight up against something in back. Can't tell if it is wood or brick. Are you going to have enough room there for wiring even if you can get a knockout out? From the looks of the KOs on the side I would say they have to be knocked from the outside in unless you can get a sharp edge of a knife or screwdriver under an edge. (Don't plan on using those tools again for their intended purpose if you are successful. ) You might be better off cutting the hole for your new outlet from outside next to the existing box and using a side KO and an offset nipple.

 
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Old 04-14-21, 05:51 PM
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I agree with 2john02458; no useable, if any, space behind that box.

That being said, to remove a knockout from the back of a box drill a hole in the knockout and run a sheet metal screw in it. Grab the screw with you lineman's pliers and PULL. Once it starts to breaks loose, push and pull. Once you can get it to about 45 degrees, grab it with pliers and twist it loose. I usually start with a 1/8" hole and a #6 screw, going larger it the hole strips out.
 
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Old 04-14-21, 06:00 PM
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Thank you for your input.

It's stucco on the other side. I'm guessing that there is sheathing underneath the stucco, so it should be relatively easy to get through to the other side once I remove the KO. There isn't any brick, masonry or concrete for sure and the wall appears less than 5" thick.

Could I open a hole on the other side slightly below the existing outlet and then tie everything together in the new exterior box? I have a raised foundation, so the proposed exterior receptacle would still be at least 2' above grade.

 
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Old 04-14-21, 06:57 PM
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There does not appear to be any available KO at the bottom. (Also looks like a conduit system.) Adding a box to one side from outside should be possible with nipple connection through side KO.
 
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Old 04-14-21, 09:02 PM
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I think you are right that it's conduit in the wall. I'll try the hole/screw method and report back. Thank you for the suggestion!
 
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Old 04-15-21, 02:53 AM
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Don't let a nipple extend too far into either box. Check how far a common fitting extends into a box.

A sturdy ice pick is often the best choice for removing side knockouts. Unless you are working in a cabinet with enough room for a drill with a bit in the chuck, the drill/screw/pull process is usually limited to knockouts in the back of a box.
 
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Old 04-15-21, 06:32 AM
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Don't let a nipple extend too far into either box.
A locknut on the nipple on the outside of the box in addition to the one inside can be used to limit how far the nipple extends into the box. Set the inside nut for minimal intrusion and tighten the other.
 
 

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