electrical
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?
Based on the information you've provided; and without knowing what TL, TR, and BR stand for, I'd say your proposed wiring looks correct. However, this is assuming that TL is the feed, and that TR and BR are devices you want to turn on/off.
If you don't trust a ground, don't connect to it - use GFCI instead.
If a GFCI won't trip with its own internal test button, it is duff. Into the trash it goes.
Here is how GFCIs and ground wires are supposed to relate to each other -- or to be more precise, how they are not.
To the left you see unprotected hot and neutral coming in, out the right you see protected hot and neutral, which I've recolored. Ground sails right by unconnected (normally). Obviously, if your ground is corrupt/defective, this is bad news indeed.
"Wait, all the GFCI's I've ever seen have a ground screw." No. That thing you call a GFCI is actually a GFCI+receptacle combination device. It provides a GFCI module, and also two sockets (wired past the GFCI). The GFCI can't use ground. Look at a GFCI breaker, it doesn't even have access to ground. The ground is for the sockets. This means effectively, that ground screw is on the "protected" side of the GFCI.
So if the ground is bad, where should you cut the ground? Before it reaches any protected loads, and remember, the ground screw on a GFCI+receptacle combo serves the protected loads.
Should you do anything creative like tie the protected-side ground into protected-side neutral? No No No! This post of mine explains how that utterly defeats the GFCI protection. Wrap the ground wires with tape so they can't touch, and don't use them.
If your panel is set up this way, the single easiest way to test your neutral-ground isolation is to disconnect your neutral-ground bond in your main service panel. Now the only thing connecting neutral and ground is that long path of dirt between your grounding electrode system and the pole transformer's. If you also unhook your grounding electrode, your house's internal grounds should be fully isolated from neutral, and should megger out at a couple megaohms. (Don't megger things in residences though, it could fry electronics).
Or test circuit by circuit. It's a simple thing, on any given circuit there should be 0.000 amps of current flow on the ground wire. Nothing is supposed to use ground but test equipment. Now, if neutral and ground are tied together, current follows all paths in proportion to their conductance (1/resistance) so a significant fraction of current will take ground instead of neutral (assuming there is a load). Obviously a GFCI will detect the shortfall, but a clamp meter will detect the ground current directly.
I don't agree with that video's claim of nearly 1 ohm between neutral and ground. Copper wires have much better conductivity than that unless he has many hundreds of feet of wire between his lab and his main panel. There may be something peculiar going on in his test lab, or he is misunderstanding or misusing the equipment. You shouldn't have 1 ohm neutral-ground, that would limit dead-short current to 120A, which would not flow enough current to safely magnetic-trip a breaker.
In any case, a clamp ammeter around the N-G bond (or a circuit's ground wire) would soon show if any AC current was flowing.
Best Answer
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.
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.