3

Let's say I have a 200 amp breaker panel that is flush mount. I want to wire in an EVSE across the garage using conduit. Somehow I need to make that transition for the conduit from behind the drywall to conduit on the surface of the drywall. I believe a junction box is the right way to do this. The obvious solution is a surface mount junction box and have conduit enter it from the back, turn in the box, and come out the side to continue on the rest of the way.

I'm wondering, can I get a deep (> 6") junction box and have it partially in the wall and partially exposed so that the conduit from the panel could come in through the top of the box on the back half and exit out the side on the front half? I would probably mount the box to the wall stud on the side of the box.

   ----
   |  |
   |  | breaker panel
   |  |
   ----
    |
    |  conduit behind drywall
    |  
    ---
    | |  junction box
    | |-------------------  <- conduit on surface of drywall to EVSE
    ---

Can a conduit body be used in this way instead of a junction box (assuming a sweep elbow fits in the stud space to change from down to out)?

It's a 2"x6" exterior wall. Will be using PVC schedule 80 conduit on the exposed run.

4

Yes you can have a box in the wall and exposed. Also schedule 80 for the exposed run will be fine. The only issue I see in your drawing is the face of the junction box is where you have the conduit coming out. The face of the box must be accessible (have to be able to open it) but coming out the side will be fine.

4

You can certainly do it with a junction box (in the wall) an an extension ring (out of the wall.) I don't know if there's anything against using a deep box halfway out of the wall as you suggest or not.

If a sweep fits, an LB will do - or if you don't actually need a pull point there, an offset through the surface of the wall will also do. Just make sure it adds up to less than 360° in bends between pull points. i.e. you are in conduit on both side of the drywall surface, there's no transition. You need a box if it's cable on one part and conduit on the other - if it's all conduit, bring it through the wall, mud and paint the wall around the conduit penetration (or use fireblock foam/caulk if the wall requires, or a fancy fire collar if the LAHJ insists) and keep going.

4

You might be making it harder than it is.

Come down out of the service panel to a flush mount junction box. I might use a 4-11/16" because it will be more versatile and it's easier to find with knockouts for 1” conduit.

That's a perfectly ordinary installation that can be adapted to many uses.

Then, slap an extension box on top of it. The extension box will have appropriate knockouts on the side, come out of that with surface conduit or regular conduit.

4
  • A Raco 187 works good for this, mount horizontal and mount to two device box or mud ring using 4 small screw holes. You are limited to 3/4" conduit, but 40% fill is not a problem, 3@#8 and 1@10 is only 26% sch40 pvc fill. May 1 at 1:30
  • 32% sch80 pvc fill, but question why sch80? May 1 at 1:46
  • Schedule 80 because it will all be exposed to potential damage. May 1 at 13:37
  • EMT may be a better choice if you're not married to plastic. EMT handles the ground path for you, so one less wire. It's also much better at the jobs we use conduit and junction boxes for, e.g. damage resistance and ability to contain arcing (it just arcs to box and that trips the breaker). May 1 at 19:37
3

Junction boxes can be fittied with only the face showing (as is common in finished rooms) or on the surface of the wall (more common in industrial settings). there are different boxes for the two applications.

fitting one half-exposed seems perverse: getting a good transision to drywall could be tricky.

It seems to me that you could mount a junction box on the surface of the wall and have the conduit enter through the drywall from the back and exit from the side.

You could do the same thing use an ell back conduit body. (LB body)

enter image description here

2

Just a note, if you're not close to your bend limit, you may not need a JB. If you have a conduit bender it is not particularly hard to offset a pipe to the surface of a wall. Just bend your offset to the correct depth, install it, install drywall around it with a 1/4" gap for caulk, caulk the hole for a nice look, and continue the pipe once the surface is finished. If the wall is a fire wall you need fire caulk. This can be made to look very clean and professional.

If you do want a box and the depth your pipe runs behind the wall is compliant, you can also add a 90 and put a connector on it so when the boarding is on you can just attach the connector to a knockout on the back of a surface mount box or screw on an LB.

1

I think you shall install a junction box just as usually done, then with the cover shown below, you can connect the exposed conduit through the hole (with applicable fittings/connectors).

enter image description here enter image description here enter image description here enter image description here

2
  • You have to be able to remove the cover. Which won't be happening with a chunk of schedule 80 PVC attached to the cover and the wall. These covers have a very limited scope of use, and this ain't it.
    – Ecnerwal
    Apr 30 at 21:59
  • 3
    This has merit, but it would need to be flexible conduit I think. Otherwise the conduit would render the j-box inaccessible. Apr 30 at 22:52

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