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How can I mount a relay socket (such as this one) to a junction box with a blank cover in a way that:

  1. complies with the 2014 NEC
  2. won't surprise the next electrician working on the circuit (as I suspect mounting it to the cover plate would)
  3. allows wiring to be connected without having to "stuff" the socket into the box with wires already attached
  4. and allows the relay to be replaced without having to detach the socket from the box?

(This is not quite a dupe of my other relay mounting question as this question deals with socket type relays while the previous one dealt with chassis mount relays, which shouldn't be used directly in mains wiring because they're not fully UL listed for standalone service.)

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  • The way I have seen it commonly done is use a box big enough to mount the socket and relay inside plus enough clearance for wiring access. Is this a trick question? – user39367 Nov 18 '15 at 4:24
  • @chris -- No, if that's the way to go I suppose it's the way to go :) given a relay socket like the one linked, how big would the box need to be to accommodate the relay + wiring without making it a cram job during installation, though? (I asked this because I was kind of wondering if it'd be possible to get a "blank yoke" and screw the socket to it, then mount it just like a receptacle or standard switch) – ThreePhaseEel Nov 18 '15 at 4:26
  • Most of the relay types I have seen that are meant for the referenced socket should fit into a 6x6x4 box, although there might not be enough height clearance to mount it using a DIN rail, and some of the 8 pin socket relays are rather tall. I have not seen the sort of "blank yoke" you describe. In larger boxes these relay sockets are usually mounted on DIN rails. – user39367 Nov 18 '15 at 4:33
  • @chris -- write up an answer and I'll toss you an upvote bone then :) – ThreePhaseEel Nov 18 '15 at 4:48
  • Eh, I do not feel like it just now. Thanks anyhow. The dimensions I gave you were from measuring the 8 pin DIN socket and relay that I threw in my garage some time ago. I make no guarantees. – user39367 Nov 18 '15 at 5:01
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The base you show is ~1" and page 8 here: http://www.farnell.com/datasheets/722224.pdf Shows a standard relay at just over 2".

It should fit just fine in a 4" deep screw cover junction box if you mount the base to the bottom of the box. Don't mount it to the cover.

However, if you plan to use a time delay relay or some other type then check the dimensions before you buy your jbox.

Depending on your application, you might consider a solid state relay such as this: http://www.amazon.com/AC-AC-80-280VAC-24-380VAC-SSR-40AA-Solid/dp/B00976EJXC/ref=sr_1_1?ie=UTF8&qid=1447848272&sr=8-1&keywords=AC+relay

It is only 1.5" high so could be mounted in a 2 ⅛" deep 4" or 4-11/16 box. Happy Day!

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Even if the relay is OK with the heat, it's nice to give yourself some room in there so you can get to the terminals. Troubleshooting might involve pulling just one wire from one terminal. Smallest possible box mounted between joists overhead: painful. Roomy box mounted on the wall at a reasonable height: happy. A short piece of DIN rail makes it much easier to detach and re-attach the relay and wire it outside the box, replace the relay, etc.

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