Properly Splice Aluminum Wire




Introduction: Properly Splice Aluminum Wire

In this Instructable, I'm going to teach you how how to make proper aluminum wire connections to ensure that they do not heat up, arc, and/or catch fire like many improperly performed splices have been known to do.

Note that this guide will also work for splicing aluminum wire to another aluminum wire, as long as you follow the wire preparation steps for both of the wires.

Always make sure the power is OFF and test this with a non-contact voltage detector and a multimeter before doing any electrical work.

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Step 1: Tools & Materials

You will need the following tools and materials to splice aluminum wire:

  • Pliers
  • Q-tip or similar application device
  • Sandpaper
  • Electrical tape (optional)
  • Approved aluminum to copper/aluminum wire nut (eg: Ideal purple "Twister" connector.)
  • Aluminum wire anti-oxidant compound

Make sure your wire nut is an approved and listed wire nut intended for this purpose. Normal wire nuts will not work. It's alright if the wire nut has preapplied antioxidant compound. It won't hurt anything, but we will not b relying on it in this case.

Step 2: Get Your Wires

You'll of course need some wires to splice. They would of course generally be inside of a box in a wall or ceiling, but for this guide I'm using a couple of cut-offs from previous projects.

Step 3: Prepare the Wires

Before you perform the splice, you must first prepare the wires you will be splicing.

To do this, first take your sandpaper and thoroughly sand the exposed bit of aluminum wire, to remove any present oxidation that would otherwise ruin the connection. Next, you must take the q-tip and use it to apply a generous amount of anti-oxidant compound to the wire. Take the sandpaper again, and use it to work the compound into the wire. Afterwards, apply a little bit more without working it in, just to be safe.

If you're splicing aluminum to aluminum, repeat the above steps with the second wire. If you're splicing aluminum to copper, you may apply some of the antioxidant compound to the copper wire as well, as it most certainly won't hurt anything and will probably further ensure a good connection.

The image is of the prepared aluminum wire. It looks a little bit messy, but that is alright.

Step 4: Line Up the Wires

Line your wires up next to each other, using one of your hands to hold them firmly side by side. If one of the wires sticks out further than the other, use the cutting notch in your pliers (or simply a pair of wire cutters) to trim the longer one.

As you can see in the photo, I've applied some antioxidant compound to the copper wire as well, as described in the previous step.

Step 5: Twist Them Together

Use your pliers to twist the wires firmly together. You must ensure that both of the wires are twisted around each other and not one wire around the other while the second wire is still straight. This is critical to both the mechanical and electrical integrity of the splice.

Step 6: Add the Wire Nut

Finally, to complete the splice, you must twist on your wire nut. Make sure to press the wires in as far as they will go, and then twist until it won't twist any further (without extreme force). This completes the splice.

Optionally, you may also wrap one or two turns of electrical tape around the bottom of the wire nut. This tape should not be holding the nut onto the splice; if it is, you've done something wrong. I personally do this to prevent any foreign objects from entering into the wire nut (although this should never happen when properly installed inside a box). Mostly, though, it's just for my own additional peace of mind.

Step 7: What Happens If You Don't Follow This Guide Correctly

Your splice is complete now and will last as long as the house it's in if you've followed the guide correctly, but I've added this additional step to show you what happens if you don't follow this guide and just sloppily make a bad splice.

These are photos (which do not belong to me) of incorrectly performed splices which have overheated, caught fire, and melted. Stuff like this often happens because the wires themselves are badly connected to each other, so instead, the metal spring inside of the wire nut (which was never meant to conduct electricity at all) starts carrying the current instead, eventually heating up and catching the plastic on fire.

This usually happens if you:

  • Don't twist the wires together
  • Rely on preapplied antioxidant inside of the wire nut instead of your own
  • Use the wrong wire nut

Please don't do any of those things, and instead follow this guide, not only for your safety but also to comply with electrical code.

Thanks for reading. Hopefully I've helped someone out with performing better and safer aluminum wire splices.

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    9 Discussions


    3 years ago

    Wintergoat, I just realized that this is from two years ago, but I'll respond anyway.

    The first thing you should mention is make sure the power is off before you start working. This is a good general rule and should apply to any electrical job (even if you're a pro). In your photo you show needle nose pliers. Using linesman's pliers is easier. There's more surface area. You won't have to stick the wires as far down on them as you would the needle nose pliers.

    The purple wire nuts are UL listed and approved. Is any method perfect (maybe other than exothermic welds)? Probably not. Thanks and good luck.


    Reply 3 years ago

    I'll add that, just to be safe! As for the pliers, you're right - I now own a proper pair of linesman's and use them for my electrical work.


    5 years ago

    Have you verified this meets NEC code? I don't believe the use of a wire nut when splicing Al to Cu meets code. Al has a different thermal coefficient and will expand and contract at a greater rate than Cu which can lead to problems.


    Reply 5 years ago on Introduction

    I'm in the US, an electrician friend of mine told me to specifically get the purple wire nut caps. I started looking into this because my a wall socket in my neighbor's house caught fire due to the aluminum wiring. Luckily their house did not burn down.

    My house was built in the same year so I'm a bit worried.

    Good information about adding the extra antioxidant compound.


    Reply 5 years ago on Introduction

    Alright, after just a little bit of research, as far as I can tell, Ideal's purple wire nuts that I've used here are in fact listed in the NEC for use for connections like this. I am, however, not a licensed electrician, and I would always check with a licensed electrician, and get all work inspected.


    Reply 5 years ago on Introduction

    I, personally, am in Canada, and I know it meets code here as long as you use the proper wire nuts

    I am not 100% sure about the USA, anyone there might want to look that up.


    5 years ago on Introduction

    Don't know if you got your image from this page or not, but if you did, perhaps you should re-read it.

    Another page to read:

    Unfortunately there's not a whole lot in the code book on AL wiring, and I'm not about to start thumbing through that at 4am. The only time we've ever used AL wiring is for feeders. With it being so big, the only place we've terminated AL wiring is under a panel lug, or a polaris tap

    When in doubt, head over to Mike Holt's forum (which I'm also not about to do at 4am and my eyes are going in and out... lol)


    Reply 5 years ago on Introduction

    I did not, I've had this set of images laying around for at least a year.

    I don't really see what I need to read on that page. Oxidation is taken care of by sanding the wires and applying compound, and loosening of the connection is taken care of by properly twisting the wires. Personally, I've had at least 20 splices made in this manner working fine for >5 years.


    Reply 5 years ago on Introduction

    Even better: