Piggybacking a junction box

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  #1  
Old 01-30-15, 06:38 PM
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Piggybacking a junction box

I want to add a receptacle in a closet because I want to move my WIFI router in there.

So I opened up the switch plate cover to the closet light switch, thinking perhaps I can add a receptacle there. I think I just opened a can of worms.

First, the cover plate will not come off, turned out it was packed full of adhesive caulk...after prying it out, the switch box itself was "caulked" to the wall board, instead of nailed or screwed to framing. There is a piece of 12-2 NM cable that comes in through the KO hole (no connector used). I then removed the switch box. As you can see, this is inside the closet.



If I peak into the hole, I can see the back side of another metal box where the NM cable comes from, what the? So I looked on the other side of the wall, well, that happens to be the tiny closet where the central AC unit is.



If I peek behind the air handler unit, I can see a blank cover plate on the wall. Can't get to it, but I can see it. The air handler is in the way. So QUESTION #1, this junction box can be seen, but can't be reached, not without removing the air handler first, I have a problem.

So I am guessing, at one point in time, the switch to the closet light is on the outside of the wall. Then they added the central AC system, so they closed off that switch box, and put in a new switch box inside the closet, on the other side of that wall. So this is what I have.



Why they didn't just free up that switch box, turn it around, and add an extension ring to it, I don't know. So here is a close up picture of the back of the old switch box, note that there is an EMT conduit connected to it up top.



If I can access that box from the AC side, I would redo the connection, but I can't. So here is my plan.

I would like to mount a 4" square metal box to the back of the old switch box WITHOUT any conduit or tubing in between (because I can't access the front side of that box to make the connection). I will enlarge the hole in the wall, to accommodate a square box, such that the 3/4" KO hole will align directly onto the plastic NM connector of the old switch box. Then I will tap and drill two 10-24 holes, and use 10-24 machine screws to connect the two boxes back to back. If the new box is recessed into the wall cavity, I will use an extension ring or mud ring to get it to sit flush. Like this:



Thoughts? If I have an attic I will do it differently, but this is a flat roof with no attic.

By the way, this doesn't solve my receptacle issue, as there is no neutral in this box, so I need to find another way.
 
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Old 01-31-15, 04:16 AM
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I think your plan of attack will work, although it still leaves the "accessibility" of the other box in question. Should anything go wrong with the conduit wiring and the NM wiring in that box, you can't access it. However, technically it is not hidden in the wall and is accessible with the removal of the air handler. It is a switch loop and there is no neutral, as you have stated. Will you be using it as a switch or a receptacle/switch? Having conduit you could possibly run a neutral from its origin into and through the box and out your new box (before you attach the new one). If so, you can have the best of both worlds.
 
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Old 01-31-15, 05:38 AM
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Here is a thought,if that buried box doesn't have a plate on it you maybe able to cut the box bracket off with a Sawsall,stick the blade through next to the stud and cut and spin the box around, that may give you an option to get a neutral up through the pipe.
Geo
 
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Old 01-31-15, 07:44 AM
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It is a switch loop and there is no neutral, as you have stated.
Do we really know it is just a switch loop in the box facing the airhandler? I don't think so, there could be a neutral in that box, but we really don't know.

you maybe able to cut the box bracket off with a Sawsall,stick the blade through next to the stud and cut and spin the box around, that may give you an option to get a neutral up through the pipe.
I agree with Geo on this one. This would make the existing box accessible and allow the OP to find out if there is a neutral in it. If no neutral, there has to be one at the light and it's a short pull to get one to the switch box. There will be some drywall to repair, but that would be normal when you find a mess like this.
 
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Old 01-31-15, 07:48 AM
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chandler I can't put a receptacle there unless I can find a way to get a neutral there.

I removed the light in the ceiling and looked up the box and yes that was the first stop, then the hot and switch leg went down that EMT conduit to the old box facing the wrong way. However those are solid conductors and I never had luck feeding new conductors through existing solid ones unless I pull them all out.

I don't think I can feed a new neutral conductor down this way since I can't get to the inside of the box to pull wire or even make a connection.
 
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Old 01-31-15, 07:56 AM
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Do we really know it is just a switch loop in the box facing the airhandler? I don't think so, there could be a neutral in that box, but we really don't know.
There isn't, because after I removed the light I can see the other side of the EMT conduit feeding that old switch box. There are only two conductors going in, two black solid #12s. So inside that old box, the two black conductors are connected to a short piece of NM that they stuck out the back of it.

Here is a thought,if that buried box doesn't have a plate on it you maybe able to cut the box bracket off with a Sawsall,stick the blade through next to the stud and cut and spin the box around, that may give you an option to get a neutral up through the pipe.
Geo
There is a cover plate on it. I can see it on the air handler side with a flash light through a sliver of space. If I try to spin it I will have to cut the wall board all around it from the closet side.
 
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Old 01-31-15, 08:04 AM
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Another option which I really hate to consider, and is made complicated by the wood middle plate right above the old box, is to go up two feet or so on the closet side, and open a 10" wide 18" hole. I should see the old conduit then.

I can cut the conduit with a close quarter tubing cutter. Then try and wrestle the remaining conduit down the old box free...I can't get to the set screw either, it's inside the middle plate. If I can get it free somehow with the remaining conductors in place, I can put a new coupling onto the EMT, then bend a piece of offset EMT and put in a junction box up higher. Then I can pull a neutral in from the light, then fed them all down to the old switch location, and totally abandon the old box facing the wrong way.

I am just really not into cutting these old thick one inch plastered walls.

Oh wait, I also have to notch out a new channel for the EMT on this side of the middle plate.
 
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Old 01-31-15, 08:56 AM
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How many conductors are coming out the back of that box? It's hard to tell from the pics ,but looks like 4 to me,where is this blocking you mentioned? Is the plate on the box metal or plastic,I would try an cut around the box and spin it you should be able to loosen the lock nut by working the box around.
Use the solid 12 as a snake and pull in new stranded
Geo
 
  #9  
Old 01-31-15, 09:29 AM
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It's a piece of 12-2 NM cable coming out of the back of the box.

There is wood stud to the right of the box and wood middle plate right above the box, if you look at the last picture, you can see the wood plate notched for the conduit.

The more I think about it, the easier approach may be just to add an extension hexagon ring to the ceiling light, to lower it a bit so I can attach a new surface mount EMT run to the wall and down and surface mount a new box for the receptacle and switch, and completely abandon that box and run. It's a closet so I am not that fuzzy.
 
  #10  
Old 01-31-15, 11:20 AM
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You could also use surface race. It would look better if you ever wanted to sell.
 
  #11  
Old 01-31-15, 11:23 AM
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It really should not be that hard to remove two small conductors in conduit.
 
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