Connectors: Which is the Weakest Link

Here we test 6 common connectors used for household wiring: A standard wire nut aka Marr connector, a heavier duty wire nut Marrette connector, an Ideal In-Sure press-in connector, a Wago 221 Lever Nut connector, a regular 120V outlet connecting wires with its internal press-in connector, and a regular 120V outlet connecting wires with with screw connectors. We try ever increasing currents from 20 to 70 Amps to see how they hold up to currents way beyond what they were intended for, and then finally over 270 Amps to simulate a short. Two of them even survived that.

[TheForgottenMan]

When wires are twisted together the resistive load of the wire nut is zero because the wire nut isn't need to create the connection. The push in and Wago add a resistive load because there is no direct connection between wires. They're connected by a thin piece of metal inside the housing, so the probability is higher for failure compared to the wire nut.

[andrewt]

I use stranded wire for all my electrical projects as it's easier to pull. The Wago connectors are so much easier to make connections with, and is all I use now. I also use commercial/industrial backwire clamp receptacles instead of trying to make a J hook around a screw. If I have to like on a light switch, fixture or something, I'll keep the insulation on at the end of the wire to keep it from fraying.
Someone else did one of these extreme overload tests, and Wagos performed better with stranded wire as there was more contact surface area. Either way, I don't think you'll run into issues with those under normal operating parameters. The breaker should trip long before the plastic even gets soft on a mild overload. As seen here, 40 amps only made the connector a bit warm.

[msytdc]

I'd be interested to see some wire nut connectors that are used in less than perfect conditions (without pre-twisting the copper wires in advance):
0. control of pre-twisted wire
1. clean straight wire but barely twisting the wire nut
2. clean straight wire but really torqueing on the wire nut until the insulated portion visibly starts twisting as well
3. wire pair used previously together in the same wire nut, uninstall the nut, separate the wires, put wires back together matching original twist, install new wire nut of same size
4. wires used previously in separate wire nuts combined into a new pairing, roughly straighten wire ends with pliers until they fit into the original wire nut size
5. wires used previously in separate wire nuts combined into a new pairing, no straightening, just jam them together into whatever oversize wire nut is needed to get them to fit

[REWYRED]

Would of been interesting if you threw in a commercial a d industrial spec grade receptacle that has "BACKWIRE" terminals: the ones you do indeed put the wire in the back but you have to tighten down the terminal and it clamps the wire firmly. Also they are of better construction so it be interesting to see how hot they get

[jburdman]

The Wago held up perfectly, until it didn't- which is also perfect. In an over-current situation that's the behavior I want to see. They're a second fuse. Engineering perfection. I don't want a connection to hang on until all my walls are on fire.

[Sparky-wwre]

Well that awesome test concluded what I already experienced with the backstab outlets aka speedwire. I've replaced burned up devices, and it seemed to have occurred after a space heater or air conditioner was running. Sometimes the outlet had nothing plugged into it when it burned out, because it was passing current to the rest of the circuit. In fact my employer would look at outlets and switchs to judge the laziness or lack of, the newly hired employees 🙂 Speedwire was a sign of someone who just wanted to finish a project in the least amount of time and didn't take as much pride in quality workmanship, looping around screw terminals meant the employee took pride in his or her work, and had the best interest for the occupants of the home.

[joewoodchuck]

Nice test procedure. I'm not at all surprised that the push in type outlet failed. The first time I saw one years ago sent shivers through me.

[Cristoforo]

Thank you for confirming my suspicions about wagos and any other barbed type electrical connection method; they’re weak, they have reduced surface area contact and when overloaded they will generated higher electrical resistance and heat sooner than with standard Marrs and Marrette connector, and of course wire binding terminal screws found on all electrical outlet devices (switches, receptacles, etc.).

Good demonstration

[Franktek]

The yellow twist on connector ( Marrette) is designed to be installed on untwisted wires. The black set screw connector is called a Marr. Both are Leviton products.

[PaulSteMarie]

You should try this with commercial or industrial grade devices with back wire contacts: two interlocking serrated brass plates with a screw to clamp them together. Similar to a simple screw terminal, but they don't require a hook in the wire and appear to have more current-carrying cross-section.

Also, that 14 AWG wire is probably what's heating up the screw terminals.

[djratino]

My house was built in 1956. The #14 circuits have to be hooked to 20 amps for the load to hold. A lot lot of receptacles are bakelite. It doesn't melt. It just crumbles. Most of the older wirenuts had set screws. I was surprised. 🐀🐾

[jeffbransky]

Great demonstration. It would be interesting to measure the temperatures during the experiment with an infrared thermometer that displays a color image of various temperatures.

[taylorsutherland]

As a master electrician, all I can say is I approve!

It would be interesting to try this same experiment with stranded wire.

[tableseven]

Thank you. The wire nut, if done well is the best....

[SierraScout]

You might be the “Project Farm” of electromagnetics!

[Kcv]

I’d love see you test wago vs wire nut, with 4 or 5 wires in each.

I currently wire everything with wago lever style connectors and I’ve yet to have an issue. I feel like they are superior to wire nuts one you get to 3+ wires in the same connection. I find it very difficult to get 3, 4, 5 wires twisted perfectly into a nut without at least one of them being loose and sloppy. Too much room for error imo. With wago connectors, all the wires have the same connection no matter how many there are.

[clancytaylor]

I would love to see videos testing different breaker brands and trying to trip them by applying heavy loads. It would give some excellent data about which breaker is the most safe to use.

[Krankie_V]

When I replaced all the receptacles in my mobile home, many of the original ones had ONLY push-in connections. No screws available. And the manufacturer used them as junctions also, without pigtails, which means the whole load of the branch circuit was traveling through the first push in connection. Some of the receptacles were physically broken into pieces. I replaced everything with spec grade receptacles which didn't even have push in connections. I wired them in with pigtails wherever possible so the screw terminals were bearing as small of a load as possible. The main reason I did this was to upgrade everything to tamper resistant outlets since I've got a small child in the home. However the massive upgrade to the connections is more than welcomed. Before replacing the receptacles, the lights would noticeably dim when turning on a vacuum cleaner. That no longer happens. I also replaced all the light switches, using commercial grade parts. Half of them were physically broken. I'm amazed that they were still working, although they felt very mushy instead of clicking into place.

[SpeedNessRx]

This is awesome. Wish someone did the same testing with common automotive connectors like Deutsch DTM, DT and DTP, Metripack and others.

[dreednlb]

I'd like to see a similar test where you find the failure point in amps of each connector individually.