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Connecting Stranded Wire; A Better Way

Discussion in 'ELECTRICAL ISSUES - POWER YOUR MACHINES & SHOP' started by RJSakowski, Feb 26, 2015.

  1. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    Wiring up projects is much easier with stranded wire than solid. But there is a drawback when making connections with screw terminals. The strands tend to splay out giving rise to possible shorts. An answer to this problem is the use of wiring ferrules. A ferrule is a thin tube that the stranded wire is inserted into. The ferrule is the crimped to secure the wire and make a solid electrical connection. I have also tinned and soldered the wires in the ferrule. The ferrule is seated in the screw connector and the clamping screw tightened, making a secure connection. They are available to accommodate different wire gauges and strip lengths and with or without insulating bushings. They are available from McMaster Carr and major electronic supply houses.
     
  2. mksj

    mksj Active User H-M Supporter-Premium

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    Ferrules are really nice, but often depends on the terminal and application. I use crimps with spades for larger screw connectors, usually crimp and solder. High voltage screw terminals, crimp ring terminals are a bit more secure. The ferrules work well for smaller wires with push in or small screw terminals that push down/compress the wires, like VFD input terminals. With the ferrules, I like to strip the wires so they extend slightly past the tip of the ferrule when slipped on vertically. Solder under low heat or small iron at the tip so the solder runs down inside the tube, then snip the excess wire. You can also use shrink tube for added support behind the crimp if needed. They do work great and provide additional wire support.
     
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  3. mattthemuppet

    mattthemuppet Active User Active Member

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    I recently used some from HD to rewire a motor and the worked very nicely. The serrations inside the bit you poke the wire into grip extremely well - no pulling the wire out halfway through crimping it :) Only downside that I can see is that there may not be enough space around the posts to fit the ferrules. Much better connection than before though, I think the lathe the motor came with may have been thrown out as one of the start winding wires had come loose in the drum switch.
     
  4. davidh

    davidh United States Active User H-M Supporter-Premium

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    i have ben told that soldering or tinning a stranded wire will leave you with high stress section right where the heated / soldered area stops. and wires do vibrate with current running thru them, I'm told. . .
     
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  5. Eddyde

    Eddyde Active User H-M Supporter-Premium

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    Crimp or solder on terminals/ferrules are the best. But if you'e in a jam and don't have any, you can you can improvise one. Strip the wire extra long, make a loop by wrapping the end of the wire around the point where it protrudes from the insulation. Tin the whole loop with solder, then flatten it out with a hammer. this makes a good ring terminal. You can convert it into a spade, by cutting off the top of the loop. In leu of a ferrule. I bend the stripped portion into a tight u bend so that the tip is touching the point where it protrudes from the insulation and parallel to itself then tin with solder. A boot of heat-shrink tubing can be added if needed.
     
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  6. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    I have heard that too, Dave. However, in more than fifty years of making soldered connections, I could probably count on my fingers and toes the ones which failed due to breaking immediately adjacent to the soldered connection. This includes numerous connections in harsh environments ( automotive, marine, heavy machines, etc.). For a century, the electronics industry used solder as a means of connecting wires in a circuit. On the other hand, I have had many connections fail because of wires pulling out of a crimp, corrosion in the crimped connection, or individual strands being sheared because of the crimping action. This is less likely to happen with a professional crimping tool but unfortunately, I have only the hardware store version.

    My personal best practices consists of soldering all crimp connectors. I pull off the insulated sleeve prior to soldering and slide some heat shrink on the wire. After soldering, he heat shrink is slid over the connector. A properly soldered connection wicks solder up the wire past the joint which moves the stress point away from the connection. If flexing wires is a concern, I use an additional layer of heat shrink to move the stress point further up the wire.
     
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  7. Tony Wells

    Tony Wells United States Vice President Staff Member Administrator

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    I've worked on quite a few machine tools and various industrial equipment and really have come to appreciate ferrules. That especially in densely populated terminal strips or devices on DIN rails. I too have heard that at the point the solder bond stops, vibration and movement causes failures. I believe that it may be so in some cases, since you are giving up some of the integrity of the tightly woven strands when the wire is stripped, and especially if it is splayed out. I have seen a few questionable connections where this is quite credible, although I have not seen a total failure attributed to that alone. Most of the installations where I have seen stranded wire soldered and inserted under a screw head or square washer also make good use of loom wrapping, which minimizes movement, at least until someone comes in and "works" on it and snips the string.

    On larger wire (#8 and up) I have used short pieces of copper tubing to couple and splice by crimping AND soldering. A little shrink tubing and it looks decent. Probably not to strict code, but I always felt comfortable with the safety of it. I use the tubing simply because I do so little of that kind of work that I won't buy the factory ferrules. Been known to flatten the end and drill a hole and make a custom ring terminal too.

    I stumbled across an interesting white paper for those of you who may want to read a little about the subject. Be aware that it is written by a manufacturer of ferrules, but I am not so sure they could get away with too much bias.

    http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCcQFjAA&url=http://www.weidmuller.com/bausteine.net/f/7862/Weidmuller_Ferrules_White_Paper.pdf?fd=3&ei=Vo7wVI7UB4KHyQTk0IDgBw&usg=AFQjCNH5vx1BllllAGmZgAtSo09-GWzgkg&bvm=bv.87269000,d.aWw
     
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  8. dirtyjim

    dirtyjim United States Active User Active Member

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    I've started using double crimps for just about all my connections, the crimp tools are expensive and several are required but once they are done they do not come loose.
    I have three Packard crimp tools that I use depending on wire gauge, there are ratcheting crimpers that will crimp the core and wings at the same time but they only work on smaller gauge wire.
    I originally bought the crimpers for doing Packard 56 and 59 terminals on my 67 chevy so any o the wiring I replaced would match the factory crimps
     
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  9. awander

    awander United States Active User Active Member

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    Manufacturers of compression-type terminal blocks and connectors recommend against tinning any stranded wire that comes under direct compression, for the reason that over time the solder can deform and cause a loose connection.

    If you use a ferrule, this deformation should not take place, so it will do no harm to solder the wire in the ferrule, but I believe it is unnecessary, as crimped connections have been shown to be the most reliable,
     
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  10. Bill C.

    Bill C. United States Active User Active Member

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    What do machine manufacturers do? I worked in a shop that made specialized machinery. I think they used closed eyelet crimped connectors, its been a long time ago. One man did about all their wiring.
     
  11. mksj

    mksj Active User H-M Supporter-Premium

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    You do not see manufactures solder crimps, because it defeats the purpose of using them in the first place. Speed of manufacturing with uniform connection, but I do not see them using crimps and manual crimping tools commonly used by hobbiests. I have often read of electricians and hobbyist's having problems with poor manual crimps and problems with uniform crimps using the typical inexpensive crimping tools. Wires can also be damaged from using too much force on a crimp. I have often seen crimps come loose and corrode (increased electrical resistance) over time. The vibration stresses to break wire over time in the hobby environment would be far less likely, than a non-manufacturer crimped wire coming loose. With high voltage wires, as mentioned, crimp, solder at the tip, and for added protection use fusable shrink tubing. They sell crimps (3M) that include a fusable insulator. Improper securing of wires is also a factor in breakage from vibration.
     
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  12. Bill C.

    Bill C. United States Active User Active Member

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    Th
    Thank you. I would walk past this man doing the wiring from a blue print. Its been over 40 years ago. A lot of changes and improvements since then. Appreciate your insight.
     
  13. uncle harry

    uncle harry United States Active User Active Member

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    I agree with using ferrules and using an appropriate crimping tool as well. NFPA79 2012 which affects all machine tool and special machinery wiring states that stranded wires shall not be tinned or soldered unless the connection is specifically designed for soldering. An example of allowing solder is a connection to a pot or solder terminal. I prefer to abide by NFPA79 since I occasionally build special machines for local businesses.
     
  14. mksj

    mksj Active User H-M Supporter-Premium

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    NFPA79 guidance has to do with connections to devices, I did not see any specifics to the crimp terminal itself, and is somewhat specific to the type of connection/terminals. The same applies to the NFPA70 National Electrical Code, which in most terminations at terminals are specific to use of bare wire.
    13.1.1.5 Soldered connections shall only be permitted where terminals are provided that are identified for soldering.
    13.1.1.8 Means of retaining conductor strands shall be provided when terminating conductors at devices or terminals that are not equipped with this facility. Solder shall not be used for that purpose.
    13.5.9.4 Soldered or insulation-piercing–type connectors (lugs) shall not be used. (for motor connections)

    They are somewhat different issues. A soldered sire, which is then crimped or just soldered and attached to a terminal, does not allow the wires to move and fill the area, i.e. a single point of contact. This is somewhat like a cold joint, and the solder will also cold flow making the connection come loose with time. There is also the added issue, that people tend to over tighten connection terminals, often breaking or damaging the wire. One reason why most terminals have specific torque specifications, and are specific to acceptable terminations to be used.

    Good crimping/connections is all about minimizing the void volume, thus most professional crimping devices provide circumferential crimping. Even with this, in some circumstances it is preferable to solder the "compressed" joint to eliminate any void are and prevent future corrosion.
    Crimps.jpg
    Having worked in the boat building environment many decades ago, this was usual and common practice for smaller wires. Example below.
    http://www.uscg.mil/hq/cg4/cg432/docs/techsheets/2010-02.pdf
    "Lugs are available in tinned copper which avoids the corrosion issue at the crimp and under the screw terminal and battery lug. Lugs can be purchased insulated or non-insulated. Insulated lugs are generally used if they are crimped in the field. Non-insulated lugs are used if heat shrink tubing is applied over the termination after the lug is crimped and/or soldered. When soldering, slide a piece of heat shrink up the insulated conductor, apply a liquid or paste rosin flux to the wire, insert into the lug, apply heat to the barrel of the lug and insert solder into the end of the barrel until it is drawn into the strands. Do not use too much solder as it will wick up the wire past the lug and cause the wire to lose flexibility. Slide the heat shrink over the barrel after it cools and use a heat gun to shrink the tubing in place, sealing the insulation and lug to prevent moisture from wicking up the conductor."

    If you want additional bedtime reading, this is how NASA does it. http://www.hq.nasa.gov/office/codeq/doctree/87394.pdf
    Ferule with solder is one form of connections for termination.

    My main concern is that standard crimping tools sold do a very poor job of making a safe connection, just try it and then try to pull on the wire and see if it moves or pulls out. I always do this after crimping, and you would be surprised how often the wire pulls out. Proper soldering at the tip fills the voids, and minimizes the risk of pullout/corrosion. That along with heat shrink tubing, especially the fusible kind make for a very stable connection.

    To address the topic of this post, ferrules, however you want to use them are great.
     
    Last edited: Mar 1, 2015
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  15. Tony Wells

    Tony Wells United States Vice President Staff Member Administrator

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    That picture looks familiar......oh, that's right! It was in that WhitePaper I linked to.
     
  16. CluelessNewB

    CluelessNewB Active Resistor H-M Supporter-Premium

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    I have never had a problem with good quality crimp on insulated terminals when using a ratcheting crimper. Those combined crimper / wire strippers are fine for an emergency tool in the tool box behind the seat of the truck but for serious work a decent quality ratcheting crimper is the right thing to use. good_crimper.jpeg bad_tool.jpg
     
  17. BoliverShagnasti

    BoliverShagnasti United States Iron Registered Member

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    You can also, depending on the size of the strands of the wires, turn the wire ends counterclockwise and then wrap to the right.
    When the screw tightens it pulls the individual twists toward the direction of the screw and the wires don't spread out.

    If you have enough screw you can add an under the screw clamp. It looks like a flat square washer with grooves in it.
     
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  18. Millbo

    Millbo United States Active User Active Member

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    I'll second the Weidmuller tools.
    I have half a dozen of them that I use at work and their quality can't be beat.
    I have two of their Ferral crimpers. The PZ-6 Roto and the PZ-6/5
     
  19. Mad Monty

    Mad Monty Iron Registered Member

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    I think MKSJ (maybe others) said, and I agree: don't solder the wires before you wrap, crimp, clamp, or screw them down. The solder is relatively soft and can yield and deform, loosening the connection. Soldering after has a pretty small chance of causing a problem, and does prevent corrosion between the wire and terminal. Everyone knows to use rosin core solder, not acid core from the roofer's world, right?
     

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