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I want to install external outlets to my attic. The wiring will be in conduit. Is it better to have a junction box for each outlet as illustrated below as A, or is there a simple solution to avoid them for each outlet, as illustrated in B below?A: with junction box for each outlet. B: Outlet as junction box

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  • What do you mean by "external outlets"? Does this mean the conduit will come from outside your house then punch in for each outlet? You certainly do not need to do A, but there could be circumstances where A is easier to do (fewer bends). We would need to know more specific details of your situation to be that fine grained.
    – blarg
    Commented Jan 30, 2023 at 11:18
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    @blarg No, I meant surface mounted outlets, sorry for the confusion. The conduit will come from the floor, from a corner in the room.
    – Mikki
    Commented Jan 30, 2023 at 11:36
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    Are your joists rated for that?
    – Huesmann
    Commented Jan 30, 2023 at 12:07
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    You really need advice from someone who knows the products and terminology where you live. From the way you have drawn the sockets I would guess you are somewhere in mainland Europe. I have just downvoted two US-centric answers. Commented Jan 30, 2023 at 15:21
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    As @PeterGreen suggests, some rules are location specific and others are based on physics (like wire size). If it's your first renovation, it's worth picking up a guide to installing electrical wiring and devices written for your country/area. You don't want to install a wiring run or outlet only to find out that it's not right and needs to be torn out. In the US such paperback books are often found at home improvement stores and hardware stores as well as on the internet.
    – Armand
    Commented Jan 30, 2023 at 17:07

3 Answers 3

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Well, the outlet (receptacle) is in a junction box.

The way you avoid the extra junction box is to either bend the conduit up to the first box and then run it at the level of the boxes, (i.e. B) or bend U-shaped conduit to go from the outlet box down to the floor and up to the next outlet box (or the ceiling down to each outlet box - no difference, really.)

The junction box needs to be large enough for the job (box fill calculations must be done.) Tiny boxes won't be big enough to have wires going on from them and would limit you to case A. So don't use tiny boxes.

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Use residential raceway and (if you want) boxes and outlets designed for it. This achieves your "B" in a way that looks attractive and doesn't need painting.

A couple of examples of US-type things, but similar ones exist everywhere:

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You need a junction box or approved raceway for each outlet. Splices and connections need to be enclosed in a approved junction box or raceway. If you have junction boxes or raceways and outlet fittings in your "b" drawing, then that is OK. Pigtail the through run and connect to the outlets.

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