Wire nut reliability

Are there any statistics of fire incidents with these connection accessories? Are they considered equivalent to screwed terminals; or is there a justification for use of them for certain installations households etc.? Similar porcelain units were used up to the late 1950's in the UK; but were phased out for terminal chocblocks etc.
Regards

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I believe they are about as safe as twisting the wires together and wraping them in sticky tape.
Kirk Johnson "Rear Stretching Specialist"

John McLean wrote:
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I have never seen any hard statistics. However, in my experience they are reliable if they are installed properly according to the manufacrturers instructions... wires stripped to correct length, not exceeding the rated number of wires, wires in the rated size range, etc. If you remove the wire nut you will see tightly twisted conductors almost fused together. The problems I have seen with them are traceable to improper application. I have seen wire nut connections that were in fires (unrelated to the connector), and they still had the spring tightly installed, although the plastic burned away.
Ben Miller

Ben Miller wrote:
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I agree with (almost) everyone that wire nuts are reliable when used as instructed.
Some wire nuts have a spring which will expand over the wires.
Others have hard plastic behind the spring and the springs can't deform.
In my experience the expanding ones work much better.

John McLean explained :
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If they are installed correctly they are ok. However you can't use them on multi-strand cable and are not really suitable for isolating a single conductor.
They aren't used at all here in Australia; The standard connector is a BP style connector with one terminal screw for current carrying conductors and a twin screw type for earthing conductors. The drawback with this type is with single core. The screw someimes scars the copper, weakens the conductor and causes it to break.
I guess to answer your question, Wire nuts are safe as long as they are installed correctly and used in a suitable application. The same applies to all electrical connectors that meet working electrical codes and/or stanadrds.

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That would be a surprise to the manufacturer, U/L and NFPA

It happens that snipped-for-privacy@aol.com formulated :
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Well, if that is the case then I stand corrected.
I have been led to believe that the the twisting motion damaged finer strands and it made that type of connector unsuitable for use with muli-stranded cables.

wrote:
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\ No problem mate, hope you are having a happy new year. Wirenuts are the standard way to connect light fixtures here in the US and you get a few in a bag with any one you buy.

snipped-for-privacy@aol.com wrote:
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I have seen them used in australia a lot

After serious thinking F Murtz wrote :
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I've only run across them inside appliances. I can't recall ever seeing them in an intallation. I know I never used them. I only use BP connectors.

Arlowe wrote:
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I remember using them over twenty years ago in a flour mill at summer hill .The factory electrician used them

F Murtz laid this down on his screen :
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Interesting.

Arlowe wrote:
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They are approved for commercial fire alarms, or at least they were on the last job I did.

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Wire nuts reliability is about workmanship. I always twist the wires together first befors applying the wire nut. I also apply electrical tape over the wire nut where there is vibration such as motor terminal housings. It is also important to read the instructions and use the correct wire nut for the size and number of wires. At a mine job the engineers speced buchanan connectors that are a crimped connection. That was a good idea, except there weren't enough crimpers to go around and some electricians crimped them with their pliers. I opened one box and these plier crimped connectors fell off. Wirenuts with tape would have been much better.

Gerald Newton
Any connector that requires a special tool to install properly has that risk associated with it. That is why unionized electricians have a negotiated tool list that they are responsible to have with them on every single day on the job. If the job requires a particular tool, and that tool is not on the tool list, it is management's responsibility to see that no one is given that connector to install that is not also issued the appropriate installation tool. It is a management function to match materials to the job to be done AND provide any unique tool that is for only a single task as well as all cutting edges.
-- Tom Horne
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Tom Horne wrote:
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Does the company provide training on proper use of the tools, or is that something the union does?

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The job I am referring to is the Red Dog Mine Port site concentrate storage building job 70 milers north of Kotzebue, Alaska in about 1999. It was a union job (IBEW). All deliveries were by air and it took a week or two to get a tool. The electricians were under the gun to produce and the job covered a lot of area. A concentrate building is about 1250 feet long by 300 feet wide and had a catwalk up 90 feet from end to end It would take about 20 minutes to walk from the cat walk to the end of the job and another 20 minutes to walk back. I cannot blame an electrician from crimping the buchanan connectors with their pliers. I think there were two crimping tools for 18 electricians. Using taped wire nuts would have been much better.

Gerald Newton wrote:
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This is the second time you have refered to "taping" the wire nuts. I am not aware of any manufacturer's instructions or UL listing requirements that call for tape. In my opinion the tape is useless, and in fact I have removed tape at times to find shoddy workmanship underneath (ie. exposed conductors because the insulation was stripped too far). The problem is, you are then relying on the tape for insulation so the workmanship for applying it comes into play. For example, according to tape manufacturer's instructions, proper layering is required and the last wrap is supposed to be stretched significantly (there is a spec as to how much) to prevent unraveling.
I think the taping is just a habit handed down from generation to generation of electricians. If you install the wire nut according to instructions, it is reliable and does not require tape.
Ben Miller