Here's a link.

First time I've heard of such a thing. I went looking for more info and found this page explaining that "These interconnectors are insulating devices equivalent to NM cable and can be installed in accordance with Section 334.40(B), so if [they are] being used for rewiring in existing building, [they] can be concealed and fished."

So if that's to be believed, code really does allow them -- and seems to have allowed them for at least 16 years. What will they think of next?

If the code allowed it, I'd trust my own offset, soldered, and double-shrink-tubing insulated splices before I'd trust a gadget like this. But it doesn't allow that, so I don't hide such splices in walls (or put them anywhere else).

I wouldn't hide this gadget in a wall either, but that's me, and YMMV.

Anybody else having aluminum NM flashbacks?

LOL, a colleague of mine, one that has done a lot of electrical renno work, brought up Al as his FIIST thought. Basically it’s a junction box. I imagine the theory is that soldering is tricky. This little plastic box with the screws is more fool proof: it’s fool proof enough to bury in a wall. The powers must also think that this is less hazardous than what goes on inside a junction box . Either that or the benefits outweigh the risk .

I’m wondering if similar arguments took place with the transition from knob and tube to NM and junction boxes.

Maybe there are so many people that wirenut splices in the wall that the code people gave up and accepted a less than ideal alternative.

NEC and local codes are the bare minimum required, you can never go below those standards with materials and workmanship but you can always go above code with quality materials and craftsmanship if the proper design is taken into consideration by licensed qualified craftsmen and the necessary inspections by local inspectors.

Any splices that are not accessible are not a good idea even if code allows them because try locating one of these types of splices when they fail from age, overload and other possible failures.

Seems like the order of the day for most electricians today is to terminate wiring into outlets and switching devices (back-stabbing) which is legal by code but also is a spring loaded connection doomed to failure. Causing loss of electrical power to downstream devices, and that amounts to more return service calls to charge clients for.

I personally would never bury a splice and or do bare minimum craftsmanship, and if any of my employees did they would not be employed by me. There are still old school craftsmen that take pride in their trade and are not looking for every shortcut to gouge clients with bare minimum materials and workmanship.

"Maybe some genius has come up with the right design."

Well, maybe. I guess we can hope.

The thing is, this problem was pretty well solved a century ago, when installers of knob and tube wiring were routinely making tap splices in the walls. The splices were soldered, then taped with insulation equivalent to the wires' (a layer of self-fusing rubber tape and a layer of cloth friction tape).

Most of those tap splices that haven't been removed for updating are still working fine today.

One big difference between 1918 and now, though, is that the percentage of electrical work done by homeowners has skyrocketed. How may DIYers do you know who could properly solder a splice, tap or otherwise?

So we have wirenuts. I suspect they were originally developed to speed the pros' work, just another step in making construction faster and more profitable. But they're probably also a better choice for DIY work than solder and tape. Wirenuts have proven pretty reliable, though I've found a few improperly installed clinkers over the years, one of which nearly started a fire.

And we also have this gadget.

For it to be approved, it would have to be even more reliable than wirenuts, don't you think? Then why does it use insulation displacement? Maybe I'm missing something, but I just can't see that IDC is better than wirenuts. I also can't see it lasting 100 years like those soldered K&T splices.

But maybe that doesn't matter. Between the quality of much of today's new construction and what seems to be an increasing willingness of homeowners to radically change their houses or even tear down and rebuild, maybe some of the houses around the wiring won't be here in 100 years, either.

DavidR, going by your reasoning, they's have to be more reliable than wire nuts AND the junction box.

There is a lot of construction and heavy reno work going on near my work area. This is not a specifically electrical observation. I see a lot of newfangled devices that shift work from the field to the factory. If a new way to do something that takes time out of the tradesman's hands and shifts it to a factory, they'll buy it.

I wonder about the longevity of some novel construction techniques too. Mostly it has been newer insulation and sealing materials. Sure, getting better R value and sealing air leaks quickly and tightly is great, but how will the new materials compare with the old ways after 100 years?

"they'd have to be more reliable than wire nuts AND the junction box."

I don't see it that way, since boxes are accessible. Or at least they're supposed to be.

In a way, I agree with you. That is from the find and fix the fault standpoint. From the standpoint of fire protection, a reliable connection to prevent heating is provided by wire nuts and the backup plan is the junction box, right? Otherwise, we could just wire nut the junctions and leave them in the wall to make branch circuits and backstab or screw-connect switches and outlets on their backsides and attach them to the drywall. Oh man, this is giving me the willies.

They are used in manufactured/modular homes. They help speed the assembly once the homes are on site.

Thanks, Dan, how long ago did you observe this practice for the first time?

When I first walked down into my basement. About 2 years ago when we were house hunting.