Connecting two standard-size wires is pretty straightforward: Grab a ratchet crimper, adjust it to fit the crimp connector, strip the two wires to fit into the butt connector, slide the wires into the connector, and squeeze the crimper. The required materials are readily available: butt connectors for inline splices, ring connectors for terminal blocks, and a dab of anti-corrosive grease for the bolts and rings. Done right, these connections can survive some extremely tough conditions. In a recent test of anti-corrosion greases and connections, we demonstrated how these connections can last up to five years in the worst bilge conditions.
But what about connecting the tiny, 22-gauge leads from an LED light, cockpit instrument, or wiring harness from a multifunction display? How do you connect these with 16-gauge wire feeds from the panel? Were trained not to use wire nuts because theyre hard to seal or to provide with strain relief; they can work loose, damage finely stranded wire, and are forbidden by the American Boat and Yacht Council (ABYC). Although you can use Eurostrips in lieu of a butt-block for smaller wires, theres nothing in the marine catalog or local hardware store for direct connections with small wires. Step-down crimp connectors will work, but these can be hard to find. Soldering can work, but there are concerns about corrosion and fatigue, and both the U.S. Coast Guard and the AYBC don't approve of connections that use only solder as the sole means of connection. You are free to solder a crimp if you like, but the wire must be physically restrained in case it overheats and melts the solder.
What We Tested
We tested various methods of small-wire connection that are best understood by looking at the accompanying photos. To evaluate soldered connections, we tested the following splices: a common splice formed by twisting the wires together, a linemans splice formed by interlocking two twisted loops of wire, and a modified version of the linemans splice that we are calling a linemans half splice or half splice.
We also tested several crimp methods. The method we settled on for most jobs involved using an oversized butt connector. Because the crimp connectors for 16-gauge wire are actually size 16-14, there is some extra room in a typical butt connector. We slid a butt connector (Gardner Bender model 75-123) up the 22-gauge wire, past the stripped portion of wire, then twisted the 22- and 16-gauge wires together tightly, then slid the butt connector back down over the twisted wires, and crimped. We crimped in the middle and at the end of the butt connector, where the small wire entered. The crimp at the end grabs the insulation on the smaller wire to provide strain relief. This inline connection is fast, easy to seal, and provides some support for the 22-gauge wire. It does, however, depend on there being extra space in the crimp connector for both wires.
A similar method, which we are calling a closed-end crimp, is recommended by Practical Sailor contributor and marine electronics installer Bill Bishop. (See A Smart Easy Way to Rewire, PS July 2016 online.) This crimp involves laying both wire ends parallel and twisting them together before pushing a butt connector halfway over the twisted ends and crimping. (See photos 5, 6, and 7 in the accompanying Tight Splices for Tiny Wires.)
When making small-wire connections, be sure to use good-quality tools, including wire cutters, insulation strippers, and ratchet crimpers. Our tester had a cheap combination tool years ago, and eventually threw it in the trash after one too many bad crimps. Also, get good quality crimp connectors; Ancor and Gardner Bender have worked well for us-although the tight center-stop on the Ancor crimps precludes the inline method of crimping. Always twist the strands together before you start, and keep grease off your fingers, if you are soldering. We used Benzomatic lead-free rosin core solder, which is readily available at most hardware stores.
None of the tested connections withstood a great deal of load. A simple twisted splice came apart at less than 1 pound of pull. The wire nut failed at 2 to 4 pounds, depending on the exact manner of the twisting. The linemans splice, half splice, and crimp connection always broke the wire, although they held as much as 6 pounds.
When we heated the connections to 400 degrees, little changed: The twist splice pulled apart at a few pounds, and the others broke at the wire. The lesson here is that strain relief is essential to any connection using small wires.
Although our test was able to create reproducible failures, the strength of soldered samples can vary greatly according to wire quality. Flexible tin wire is generally preferable to brittle copper-strand wire. In tests, the crimp connector generally finished in the middle of the pack, better than stiff solder jobs, but worse than a sample where the tinning tapered gradually.
The wire nut was a surprise. It consistently held far better than soldered or crimped connections, and nearly as good as heat-shrink protected splices. We observed some damage to strands, but it was minor.
Corrosion was a problem. All of the soldered connections showed considerable galvanic corrosion where the wire met the solder, and all but one soldered sample fell apart when we were blotting them dry to take the after picture. The wire nut also showed considerable corrosion. The spliced connections showed corrosion on the tinned portions but very little on the wire.
Although solder is not recommended by the ABYC or the U.S. Coast Guard, we were interested to see whether it improved the durability of our small-wire connections.
To create a twisted splice, simply twist one wire around the other. It offers minimal structural integrity, so the connection must be soldered as well. In addition to simplicity, this also gives the smoothest result and is the easiest to make look good.
Bottom line: The twisted splice doesnt meet Coast Guard or AYBC standards and is subject to corrosion. Its not recommended for damp locations.
To do a linemans splice, you fold the heavier wire in half. Next, you lay the smaller wire in the bend of the larger wire and twist the heavier wire up tightly. Finish by wrapping the smaller wire very tightly and neatly around itself, trimming tight. (See accompanying photos.) This will not come apart, even if the wire melts, meeting the intent if not the letter of the regulation. It is, however, a bit messier to solder and protect with heat-shrink tape, since a heat-shrink tube that will fit the splice might not shrink to the dimensions of the smaller wire.
Bottom line: The linemans splice is not acceptable to ABYC, but its the most secure solder-only connection. Its not recommended for damp locations.
To create this splice, strip about 1-inch of the large wire and 2 inches of the smaller wire. Bend the larger wire in half, with the end about a quarter-inch short of touching the insulation. Thread the smaller wire through the bend, and then squeeze the bend flat with pliers. Wrap the smaller wire around the bent large wire, holding it closed. The result is similar to a sheet bend. It is very secure, easy to make, and creates a secure electrical connection, even without solder. Soldering will improve this connection for any permanent use.
Bottom line: The half splice is bulkier than other wire-splices, but it is probably the best method for a temporary connection that uses only tape.
Mechanical connections provide the surest joint, but getting the right fit requires some tinkering with different connector types and sizes. And some connectors are simply not well-suited for the marine environment.
To use a wire nut, strip about 5/8-inch of insulation off the larger wire and 1 inch off the smaller wire, then twist tightly into a pigtail. Twist the nut firmly in place. Secure the connection with several inches of tape wrapped in the same direction that the nut was twisted.
The fatigue performance of this connection was impressive. It was nearly as durable as soldered splices that were protected by heat shrink. When testers removed the nut, we noticed some damage to small wire strands, but nothing significant. Experts worry about wire nuts coming loose due to vibration and hot/cold cycles; this can happen, but it is rare, and preventable if the nuts are tightly wrapped with tape.
Bottom line: The U.S. Coast Guard allows wire nuts in specific cases (see accompanying USCG Regs and Wire Nuts top right), but the AYBC prohibits their use across the board. For most connections, especially those that might be exposed to water, we think they are a poor practice. In other words, leave these at home, or use them only for quick, temporary fixes when no other alternative is available.
The folded crimp, in which we folded one wire back over itself two or three times to increase its diameter, did not perform as well in fatigue testing as a wrapped crimp, in which the smaller wire was wrapped around the larger one before crimping. To make a wrapped crimp, strip about a half-inch from the large wire and 1 inch from the small wire. Slide the crimp a few inches over the smaller wire, twist the wires together, and slide the crimp back over the splice. Crimp as usual. This only works for wires small enough that you can still slide the twisted pair past the center stop in an AWG size 14-16 crimp fitting. In our experience, an AWG size 16 wire twisted with an AWG size 22 wire can still fit into an AWG size 14-16 crimp made by Gardner Bender, Tyco Electronics, and Ideal-but not Ancor, although these crimps are highly regarded by marine professionals.
In the closed-end crimp, the two wires are laid parallel and pushed into one end of the butt connector for crimping. This approach performed about the same as the wrapped crimp, but they are much harder to seal with heat shrink. A simple way to provide strain relief is to double the crimped connection back over the larger and wire tie it in place. (See photos in Tight Splices for Tiny Wires.) This relieves all of the strain from the connection itself.
We did not test step-down butt connectors, designed to accommodate two different wire sizes. Properly installed with ratchet crimpers, these are another solution, although we would still use heat shrink over the crimp to help provide additional strain relief and improve water resistance.
Bottom line: The wrapped crimp or the parallel crimp are our Best Choice picks for making small-wire connections.
The US Coast Guard and AYBC forbid soldering as the sole means of wire connection because of the risk of separation if overheated. This disqualifies solder-only connections from being among our top picks. Weve been told fatigue is an issue with soldered connections; perhaps this is true, but we didn't see that in testing, and certainly not after covering the connection with heat shrink. However, no soldered connection survived seawater exposure without severe corrosion damage. Additionally, since the solder triggered severe galvanic wire corrosion, we do not recommend soldering crimped connectors, even though some favor this as an improved method. In a saltwater environment, it is quite clear that solder actually makes things worse.
Our favorite method for connecting tiny lighting and instrument leads is the wrapped splice that is slid into a butt crimp connector and crimped; its fast, secure, and easy to insulate. Equally good, but not as elegant or easy to seal, is the closed-end crimp. The advantage of the closed-end crimp is that when the butt connector is folded back over the larger wire, then wire-tied and taped, there is no load on the crimp, making it plenty strong for pulling through conduits-albeit a slightly larger diameter.
If you are forced to make a temporary connection without proper tools, the linemans half splice is secure and gives a good connection with only tape, but this should only be used for very small loads and should be repaired correctly as soon as possible.