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Author Topic: Wire Nuts  (Read 9209 times)
TANAKASAN
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Posts: 933




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« on: January 07, 2013, 12:40:19 AM »

Nothing to do with Ham Radio but I'm curious about something. Over on the European side of the pond if we need to join two mains cables behind a wall then either we use a junction box with terminals or we use something referred to as a 'chocolate block' connector, see https://www.europaspares.com/images/14552/1.jpg

In the USA and Canada something called wire nuts seem to be the norm, looking like the cap on a toothpaste tube they just appear to twist on. Are these devices secure and what happens if the cable is pulled? I'm also interested in the current carrying capacity of the connection with just a twist connection.

My personal preference is to use a junction box which clamps the cable at the insulation and, separately, makes the electrical connection but I'm a belt and braces kinda guy.

Tanakasan
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K1CJS
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« Reply #1 on: January 07, 2013, 04:16:58 AM »

Any wire connections done here on this side of the pond are required to be in junction boxes with appropriate strain relief incorporated in the box itself.  Boxes cannot be hidden, either.  For solid conductors, wire nuts provide excellent connections, for stranded wire, not so much, but the connections are still good. 

Since the individual wire nuts are cone shaped, the more they're twisted on, the tighter the conductors are joined.  Of course, it's possible to overdo it, but in general, wire nuts do what they're supposed to do, and do it well enough.
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W1JKA
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« Reply #2 on: January 07, 2013, 04:33:14 AM »

    I can't comment on the chocolate box connectors but as far as wire nuts go they as you say look like toothpaste cap covers,come in various sizes to accommodate different gauge wire sizes.They usually have either a female thread insert or a coil spring inside to compress the twisted wire ends together when twisted on.Most generally used in household 120-240v wiring applications/installation allowed with national and/or local electrical wiring codes.
    They must be used in a static environment where there is NO chance of pull or strain as there is a chance of the wires themselves or wires and inserts pulling out of plastic cap and sometimes even the plastic cap itself splitting open.Be aware that theses slightly off spec and cheaper name brand nuts offered by the big box stores in the U.S  have thinner and cheaper plastic and less rugged inserts.Buy full spec name brands from reputable electrical supply vendors.
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KE3WD
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« Reply #3 on: January 07, 2013, 05:56:00 AM »

And, while they may look like toothpaste caps, the materials used in construction are much more reliable and robust than the materials used to make a common toothpaste cap. 

Inside the composite (plastic) of the wirenut itself there is a conductive threading, as mentioned, it is shaped like an inverse cone and threaded itself such that the more the wirenut is tightened down on two previously and rather lightly twisted wires, the more those wires are forced inwards towards the decreasing ID.  Makes for a rather robust connection and code here requires that such connections should be implemented inside a strain relieved box. 

The wirenut design is robust and time proven. 

After all, we are not experiencing inordinate amounts of electrical fires on this side of the pond due to poor connections...


73
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TANAKASAN
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« Reply #4 on: January 07, 2013, 06:11:08 AM »

Ah! Never having seen one of the wee beasties I didn't know about the metal insert that clamps the wires. So, with the requirement to strain relieve the connections inside a metal box things are a lot safer than they first appear.

Thanks!

Tanakasan
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KD0REQ
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« Reply #5 on: January 07, 2013, 08:57:31 AM »

the National Electric Code for North America says you have to use pliers to mechanically twist the bare wires together before using wire nuts... said twist to go down the insulation at least two turns.

there are plenty of connections inside walls (hopefully inside junction boxes with a wrap or three of PVC electrical tape for moisture protection, although you can probably knock out the walls in any house and find "blind connections" with no box, sometimes with no wire nuts!) that have not been twisted.  you can usually find them by lights that blink randomly, or dim when the furnace goes on.  sometimes they are found when the fire marshal is inspecting the scene.

Euro barrier blocks would not cut it here for line power.  there are scurvy spring-loaded backstab (spring leaf friction connector) blocks that somehow got UL certified, and I believe them to be no more reliable than backstab wiring devices, which arc and gouge the wire and usually wires fall out when you replace them with reliable screw fastened devices.  I like the Euros for LV work, but if you're a believer in that last quarter turn of the screwdriver, you can twist the terminals off the mounting strips in between.  I still like good old Cinch/Beau phenolic screw barrier blocks for thier ruggedness.

the gold standard wire nut is from Ideal, although 3M and Buchanan also have their adherents.

the standard is... if the wire slightly deforms and is held tight by the connection, without creating a fracture point, it's a good connection.  officially, if it isn't gas tight, it probably won't meet code.
« Last Edit: January 07, 2013, 09:12:57 AM by KD0REQ » Logged
K8AXW
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Posts: 3960




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« Reply #6 on: January 07, 2013, 09:04:37 AM »

CJS: I concur!  To use the "chocolate bar" method of connecting wires behind my wall board would leave me sleepless for the rest of my life!

CJS covered it very well.  There is a new (to me) product out now whereas you bring out the wiring in a box and stuff the ends into a junction block.  I have no idea if they are UL approved or meet state code.  Just a FWIW.
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G3RZP
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« Reply #7 on: January 07, 2013, 09:22:41 AM »

I have seen older wirenuts in ceramic, but I suppose that's  more expensive.
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W9GB
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Posts: 2656




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« Reply #8 on: January 07, 2013, 04:22:34 PM »

The 3M ScotchLok wire nuts are found in 120/240 VAC residential wiring.
http://multimedia.3m.com/mws/mediawebserver?mwsId=SSSSSu7zK1fslxtUnY_vMxmGev7qe17zHvTSevTSeSSSSSS--

The 3M Highland connector is common inside Lighting Fixtures.
http://multimedia.3m.com/mws/mediawebserver?mwsId=66666UuZjcFSLXTtn8Ta4xs6EVuQEcuZgVs6EVs6E666666--
« Last Edit: January 07, 2013, 04:25:54 PM by W9GB » Logged
WB2WIK
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« Reply #9 on: January 07, 2013, 06:28:23 PM »

Wire nuts work well, but they are manly things.  If you're a female electrician, there can be problems. Wink
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KE4DRN
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« Reply #10 on: January 07, 2013, 09:19:26 PM »

hi

these connectors from Tyco are available but not popular

http://www.te.com/catalog/cinf/en/c/11621/1394

73 james
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KD0REQ
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Posts: 1006




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« Reply #11 on: January 09, 2013, 10:33:22 AM »

general rule about Tyco (fka Amp)... the connectors may be inexpensive, may not be,  but there is almost always a tool involved, and the usual price is $280.
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KE3WD
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« Reply #12 on: January 09, 2013, 02:16:31 PM »

And, those type of insulation displacement connectors are not to be used on household mains wiring, inside junction boxes. 
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KE4DRN
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« Reply #13 on: January 09, 2013, 04:44:41 PM »

hi,

No special tools required, just slip joint pliers and screwdriver.
the two screws secure the strain relief not the connector,
that snaps shut with locking plate.

These connectors are use in modular home construction and are insulating devices equivalent to NM cable and can be installed in accordance with Section 334.40(B), so if is being used for rewiring in existing building, it can be concealed and finished.

http://www.ampnetconnect.com/product_groups.asp?grp_id=2307&path=0,2299

I am not a licensed electrician and local codes may or may not allow them.

73 james
« Last Edit: January 09, 2013, 04:48:34 PM by KE4DRN » Logged
AA4HA
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Posts: 1583




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« Reply #14 on: January 10, 2013, 05:01:25 AM »

Wire nuts work well, but they are manly things.  If you're a female electrician, there can be problems. Wink
That is why it is best to tighten them with a pair of pliers until they make a squeaking noise.  Cheesy
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
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