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I got this Z-Wave 40 A relay from Aeotec, but it’s got non-standard openings for wiring, and I’m not sure how to install it to code in my shop. This indoors in an industrial environment. I’m connecting a small electric water heater (20 circuit). Right now it’s connected with a few feet of 3/4" FMC with L,N,G 12 ga wires (it’s what I had on-hand).

You can see what I’m working with here. The plastic bridges don’t seem all that secure, and typical flex fittings don’t fit.

Any suggestions?

Aeotec Z-Wave Smart Switch

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    ... and that's what happens when you buy AC mains equipment off Amazon. Badly thought out on the physical side... poor fitment to US style wiring methods... what is that funny gasket thing, even? It's almost like the builders had no experience whatsoever... gee... they were saying in 2016 "we'll get UL listing next year"... not ever gonna happen... UL doesn't put up with that... – Harper - Reinstate Monica May 1 at 8:16
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The problem is, these products are conceived of by techno-geeks who are interested in the smart-home tech. Silly things like physical wiring connections are really not "thought through" in any way.

Normally electrical equipment must meet the Underwriter's Laboratories (UL) "White Book" standard, and get passed either by UL or a competing lab such as CSA or ETL. These things are pushed into the marketplace fast and cheap, bypassing that - either by direct ship from China, or dropshipped via Amazon (same effect). That's why Home Depot doesn't sell them - they can't. Even Amazon proper won't sell it, which is why it shows up in the Amazon Marketplace flea market. Mains equipment should never be bought there, nor from Banggood, DealExtreme, eBay, or AliExpress.

Right off the bat, UL would never list an item with such utterly bizarre cable and conduit attachment points. It looks like it was designed by someone with no familiarity of US wiring methods, just "freestylin'". Another obvious redflag is the lack of wire bending space and simple cubic inches for the connection. You can't cram wires like that unless they are plugs. Even their product illustration shows a wiring method that violates NEC in several ways, including unclamped sheath (and they are showing North American wire colors, so no excuse). There simply isn't enough room in the device to make proper splices.

enter image description here

How do you fit it to Code?

You don't. On the first page of Code you have NEC 110.2, which requires equipment be approved. That's officially the AHJ's call, but they universally defer to UL and other NRTLs. Without a UL etc. stamp, it will not be approved. CE is not a testing lab.

But there are so few high-amperage smart relays. What do I do?

The problem is you're trying to combine two things (high current switching, and smart gadget) into a single device. You don't need to.

You can split up the job. First, have any low-voltage smart controller that talks to your network and has a relay output capable of handling 50 ma at 24 volts. That's not a big requirement. Being an entirely low-voltage device, it doesn't even need to be UL listed. So perhaps in the $10 range, $20 at most if you find someone who is not overcharging you.

Then, you have a UL-listed transformer creating 24 V AC, then you have a UL-listed contactor actually throw the big load. As separates, each is available in the $15 range. The transformer mounts in a knockout or as a junction box cover. The contactors vary.

You can also get combo contactor-transformers in a couple of form factors:

  • Goes in a knockout, such as the "Aube" relays. They have a tiny transformer just big enough to operate the relay. The device simply gives you 2 low-voltage terminals with 24V on them: you short them, or you don't. They typically also give you access to both sides of the transformer, say if you wanted to power the smart module off the 24V transformer.

  • A larger transformer-contactor combination that replaces a junction box lid ($50-90). The device smartly puts the mains voltage on the "inside" and the thermostat wires on the outside, which complies with Code requirements to do just that.

enter image description here enter image description here

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  • Thanks for the thorough answer. Aeotec is a Silicon Valley company, but acquired a German company in 2018. My guess is this product might work in Europe, but thank you for confirming it doesn't work here. – Rick May 2 at 0:31
  • @Rick -- yeah, your smart relay was designed for IEC-style wiring methods – ThreePhaseEel May 2 at 0:52
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    @Rick That's what they claim. But everything is weird and vaprous. Their Wikipedia page is a month old and was entirely written by one person, whose only other contribs involve edit-warring and VFD on another nearly 100% self-authored page. Their Silicon Valley location is an apartment. Their Hamburg location is a flat or tiny office, 1200sf at most, I suspect a mail forwarder. Those were hard to find. The only thing that appears to be real is their Shenzhen location. – Harper - Reinstate Monica May 2 at 1:41
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    I couldn't find much on that German company. It may be a recycled brand name. They'll pay a few bucks for being able to brag they've been in business since 1930 and to claim nationality... – Harper - Reinstate Monica May 2 at 1:50
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    Right, no need to derate a contactor. All you have to do is short 2 wires that have 24VAC on them. Y'know, another way to go is operate any contactor that's UL-listed for switching water heaters, and then feed that from a 24VAC "wall wart" power supply, and then plug that into any random Z-wave "lamp controller" that switches a socket... must be hundreds of those. – Harper - Reinstate Monica May 2 at 2:05

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