How to properly install a wirenut

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seilerbird

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In another thread this morning someone was given the advise not to use a wirenut on motorhome wiring because it might vibrate loose and fall off. Well, yes it might, but not if it was installed correctly. Since I have come across so many wirenuts that were not installed correctly I thought I would post a thread on how to properly install a wirenut. It seems like it should be a simple thing but it is not.

The proper way to install a wirenut is to have a solid mechanical connection before installing the wirenut. You should use pliers to twist the wires until they are solidly intertwined with each other and then cut the ends of the wire off so that there is only about 1/2 to 3/4 of an inch of bare wires left (depending on the size of the wire. The smaller the size wire the less bare wire you should end up with.) Then twist the wirenut on as tight as you can get it with your bare hands. The end of the wirenut should cover all the bare wire. As an optional step you can add some electrical tape around the wirenut and wire for extra insurance.

The bottom line is that the wirenut should not be mechanically holding the wires together, they should have a mechanically sound connection before the wire nut is ever applied. That way if the wirenut should vibrate off then the connection is still solid.
 
Glad to hear I was doing it right.


What do you think of the wire-nut (I call them Marette, but that's a brand) that have a copper sleeve with a side screw that you put over the wires, then a plastic cover screws onto?  Like these: http://woodgears.ca/wiring/wirenut1.jpg  I find they seem to work better with large gauge wire.

 
Those will certainly work also. However in the photo the wires were just inserted into the sleeve without being made mechanically sound first.
 
Absolutely the correct technique.  One comment though.  If you do decide to put tape on the wire nut make sure you put it on in the same direction/rotation that you put on the wire nut.  If you screw the wire nut on clockwise wrap the tape in the same clockwise direction.  Helps keep it tight on the wires.  If you apply the tape in the opposite direction it wants to pull the wirenut in the direction to loosen it.
 
I have several wire nuts that,,, after nutting they taped it on.. They don't come loose either.

I have a few crimp connectors that have come loose.. but usually it is like a 14ga wire crimped to a 22ga wire or some such.
 
Came across a "new to me" type of wire nut the other day. They are for exterior use and have a bubble of what appears to be silicone in them that breaks when you start screwing on the wire nut and seals the connection and bottom of the nut. I believe they were made by Ideal. I used a couple around the house and would imagine that once the silicone set they would probably be a lot harder to get off, although I haven't tried. (would probably hold up good against vibration)
 
Good post Tom!!  Electrical issues are many times caused by simple things like improper connections.  We just tend to make them complicated.
To John's point of crimp connectors, they do make step sown connectors to connect different wire sizes.  You usually have to find them at better electrical supply stores.
 
I'll have to disagree on all of this if you read the directions from the manufacturer it says that pre twisting is not necessary. If you turn it tight enough it will twist the wires anyway. There is a type that has a spring that once turned it will not back off.

Electrical tape will hold it until it starts to degrade then it makes a mess and doesn't work anymore.

A properly sized and installed crimp connector is probably the most permanent connection.
 
glen54737 said:
A properly sized and installed crimp connector is probably the most permanent connection.
Click to expand...

Crimp connectors are notorious for coming off, the wires breaking at the strip point, or corroding internally.  If you want permanent, use solder and shrink wrap.
 
OK, a quiz... Who is right?  A great subject to ponder.

  Sounds like we need a better mousetrap.

 
If you mix enough powdered graphite in glue you make a conductive glue. So perhaps some powdered graphite lock lubricant and some waterproof glue is the perfect sealer/adhesive.
 
I like some of the automotive butt joints, especially those with a heat shrink shield built in.  However if the space is too tight, it's not possible to get a good crimp which makes them useless.
 
I would assume that the NEC code folks know what they are doing. Every book (code or otherwise) I've read says to twist the wires firmly, preferably with linemans pliers, *before* putting the wire nut on. Doing so guarantees the lowest resistance connection possible. I can't imagine expecting a wire nut to twist 12ga or 14ga solid wire reliably just by finger strength alone.
 
glen54737 said:
I'll have to disagree on all of this if you read the directions from the manufacturer it says that pre twisting is not necessary. If you turn it tight enough it will twist the wires anyway. There is a type that has a spring that once turned it will not back off.

Electrical tape will hold it until it starts to degrade then it makes a mess and doesn't work anymore.
Click to expand...

+1

As with so many things, it depends.  Of course, I'm still sitting on a boatload of tickets to my upcoming Meltfest (tm) (pat pend) (c).  A few front row seats are still available for those who can afford them.  We can add a twist-off to the planned festivities.

There have been wire nuts of several construction types throughout the grand and glorious history of the device.  They are U.L. listed as "pressure connectors," and the original ones were, as the name implied, merely threaded plastic caps that could be placed over two or more wires.  With these types a certain amount of pre-twisting was required because there was greater reliance on the pressure connection between the conductors themselves since the device had no conductive spring.  I only encounter these now in low-cost situations as when buying a lighting fixture from the cheap place that comes with a couple of wire nuts.

Newer wire nuts utilize an inner metallic spring made of material that is both springy and conductive.  These types generally don't require, or benefit from, pre-twisting of the conductors, although in a large bundle of conductors twisting may help keep the wires aligned while the wire nut is applied.
 
ttyR2 said:
I would assume that the NEC code folks know what they are doing.
Click to expand...

The NEC is silent on this topic beyond requiring that the devices be listed for the application.  The manufacturers and listing authorities specify how the devices are to be installed.

In any event, assuming that the NEC is, in its entirety, based on things like fact and science, would take a large stretch of the imagination.

Codes in the rest of the world are considerably different.
 
Water Dog said:
Came across a "new to me" type of wire nut the other day. They are for exterior use and have a bubble of what appears to be silicone in them that breaks when you start screwing on the wire nut and seals the connection and bottom of the nut. I believe they were made by Ideal. I used a couple around the house and would imagine that once the silicone set they would probably be a lot harder to get off, although I haven't tried. (would probably hold up good against vibration)
Click to expand...

All the ones I have encountered use an encapsulant (what you call the silicone) that remains in a paste-like consistency after installation and does not set up.

 
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