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I need to secure four 14 AWG solid copper wires and I have black wire nuts stamped Marrette 33, which look something like in the following photo except that the spring is copper:

enter image description here

Should it be ok? I don't have the packaging, and I have not found information on the wire limits. There seems to be a new color scheme now on newer wire nuts and wing nuts.

My impression is that four 14 AWG solid wires seem really at the limit, possibly past it. The four wires seem tightly secured in that I can't pull the wire nut off. When I undid the wire nut to check on the wires, they are quite indented by the wire nut's screw, but they did not twist together. With so many wires, they also don't go in as deep, so a couple of millimetres of the stripped part of wires is still visible below the edge of the wire nut. The wires were stripped to the same length as the textured portion of the wire nut. I estimate the wires are about 1 centimetre into the wire nut screw.

For context, this is an "inherited" situation at an outlet which has four 14/2 cables coming into the box, plus a two wire light fixture mounted to it. They are the line in, continuing line to the rest of the circuit, cable to the switch for the light fixture, plus another line to an outlet next to the fixture. This is in a bathroom.

Previously, there were up to five wires (four solid copper and one stranded wire from the fixture) attached together with solder, wire nut, and electrical tape. I have reorganized slightly by replacing the cable to the adjacent (formerly "razor only") outlet with 14/2 cable since the previous one had no ground wire, and removing it from the switched circuit. Now only 4 wires are at any connection.

I have not soldered the wires, and have just used wire nuts. Especially given how packed the box is, I'm a bit uneasy about any exposed live wires, so either I'll get larger wire nuts if these ones aren't suitable, or maybe just use electrical tape with the existing setup. Aside from not having larger wire nuts handy, I'm also hesitant due to the space constraints in this box.

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Here is a catalog from Thomas & Betts, the makers of Marrette connectors. Pages 14-15 cover the black high-temperature wire nuts including the Model 33.

The graph on Page 15 shows limits of "Min. 1 #18 + 1 #14 Max. 4 #14", so four 14AWG wires is exactly at the manufacturer's limit.

enter image description here

There's also a detailed table at the end of the document (Model 33 is covered on pages 25-26) which tops out at 2 #14 + 1 #12, 4 #14, or 2 #12.

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  • Fantastic, and thanks for the link to the manufacturer specs! Any thoughts on the exposed parts of the stripped wire under the wire nut? Should the stripped length differ based on the number of wires being joined? I'm hesitant to cut the leads shorter, and electrical tape seems messy, thought perhaps better than nothing.
    – adatum
    Oct 9, 2019 at 19:34
  • You want to make sure the exposed wires don't touch something conductive and short/electrocute. What's wrong with using electrical tape? This is exactly the use they're designed for. Screw in the wire nut, and if there are exposed wires, wrap it in electrical tape. If you want something that's nicer, use heat shrink tubing
    – Nelson
    Oct 10, 2019 at 3:09
  • @Nelson In the end I used some electrical tape and I think it turned out well.
    – adatum
    Oct 10, 2019 at 4:43
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Don't reuse old nuts, or ones of indeterminate origin.

  • Some wire-nuts are single-use; using them destroys their gripping power.
  • Wire-nut technology has moved in leaps and bounds in the last 10-20 years, and the newer nuts are much better.

Aim to use nuts near the middle of their working range

Not at their extremes. Black is not a new code, it's a older minority color code for a smallish nut, like most people's orange today. I use orange for binding 1-2 #18 + a #12 inside fluorescent fixtures, or 2-3 #18s; blue is ideal for the latter but orange(black) will do.

For four #14, I would reach first for a yellow, as four #14 is in its happy middle, on the high side. Or a red, which is also in its happy middle on the low side.

Nuts are cheap, so don't scrimp. I've searched electrician forums for what nuts they think are the best, the large majority prefer Ideal.

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  • Like the middle of the range idea... never know when you might want a pigtail.... and don't use salt shakers... (that was funny)
    – JACK
    Oct 9, 2019 at 19:13
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    Agreed especially about the "aim for the middle of the range" part. But in this case black isn't a size code, it's used for multiple sizes of their "high temperature" product family. The 33 is actually about halfway between "orange" and "yellow".
    – hobbs
    Oct 9, 2019 at 19:14
  • The wire nuts seem sturdy and grip the wires well, so I doubt they're single-use. I suspect these wire nuts have been there since the house was built. There are orange wire nuts too, and the blacks are definitely larger (no way 4 #14 would fit in orange). Ideal 74B Yellow says max 4 #14 w/ 1 #18, so seems close. Thoughts on exposed wire under the connector, appropriate stripped length vs number of wires, and/or electrical tape as a remedy?
    – adatum
    Oct 9, 2019 at 19:34
  • Perhaps you meant a different yellow connector. This document from Ideal is great, especially the Wire Range Chart on page 20. Other yellows are rated for 3 #12 which according to the chart is a bit larger than 4 #14. Interesting to notice that 5 wire connections seem the max in general.
    – adatum
    Oct 9, 2019 at 19:47
  • Turns out I had a couple of Ideal 74B wire connectors in yellow and purple (could it get any more confusing?). As far as I can tell, the dimensions are identical to the Marrette 33. I did replace one with an Ideal just to test it out, and the results are identical too. So I just used some electrical tape and called it job done. I can sleep better at night and my curiosity is satisfied too. Thank you all!
    – adatum
    Oct 10, 2019 at 4:43

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