How to Cap Off Electrical Wires (Tips)

What wire caps should I use to complete and secure the electrical wires? The best caps should be compatible with the wire gauge. Make sure the caps fit onto the twisted wire strands. The grip should be firm to prevent the caps from falling off.

Another hint to consider is using colored caps for respective wires. Use green caps for the ground wires, black caps for the black wires, and so on.

blue electrical box blue electrical box mount to a wood postmount to a wood post

In general to cap off the electrical wires in a switch box or any other electrical device, identify the polarity of the wires – not the colors.  Grab your caps and encapsulate (insert) the naked wire strands in the cap. If you do not have caps whose colors match the polarity of the wires use any color. Finally, use black adhesive tape to reinforce the caps on the wire at the bottom sections of the caps.

Before you start insulating the terminals of your electrical wires, turn off the power supply to the electrical circuit you want to work on. To do that, turn off the correct circuit breaker in the electric service panel.

a hand working on a main breaker switch box

Use the voltage tester to test all the wiring you are about to start working on. Connect the tester probe to the wire terminals in the electrical box. You are not to get any voltage value, if you get a reading, double-check the circuit breaker.

The Things You Need to Cap Off Electrical Wires

Tools You Want

  • Wire stripper
  • Voltage tester – non-conduct
  • Flat-head screwdriver
  • A utility knife

Materials

  • Electrical box
  • Electrical tape
  • Wire caps
  • Blank wall plate

Preparing the Bare Tips of the Wire

a hand holding a wire stripper

Begin by cutting the bare ends of the wires using an electrical stripper. Strip the plastic insulation at the tip of the wires to obtain about ½-inch of straight wire at the tip.

Place the Wire Caps on the Wires

a hand placing wire caps on the wire

After preparing the wire tips, the next step is encapsulating them in the wire caps or nuts. Use the correct plastic nut gauges to cap off your wires. Oversize plastic nuts will provide a loose grip which may eventually cause them to fall off exposing the naked wires. An electrical shock or electrocution may result. So, make it a point to use the correct wire cap gauges. Undersize wire caps can also fall off the wire tips exposing you and your home to danger.

Simply turn the plastic wire caps onto the tip of the wire strands and rotate it a bit clockwise. You do not need to cap the bare ground wires, unless for aesthetic purposes. (1)

Strengthening the Cap Grip with a Tape

putting a tape on the cap grip

Wire nut connection reinforcement is necessary to cancel the possibilities of your caps falling off, or exposing the wires. Naturally, all objects are subject to oscillations which causes the wire caps to slide bit by bit until they separate from the wires. To prevent that, use tape to reinforce the caps on their respective wires.

Push the Capped Wires Into the Box

a hand pushing the capped wire into the blue electrical box

After capping all the wires, push them into their box. You should double-check the wire cap connections to ascertain their grips, some wires may come apart in that event. So, be sure to check them to prevent them from coming into contact.

Add Your Blank Wall Plate Into the Box

blank wall plate

The next thing to do is to add the blank wall plate to your electrical box. Use the provided screws to achieve that.

Next, restore power once all the wires are capped – if the capped wires are part of the working circuit. Terminating the wire tips with wire caps adds a layer of safety to your home. However, if the capped wires are not part of the working circuit, no need to turn on the power.

When Should You Cap Off Your Wires?

It is usually easy to manipulate your electrical wires before a drywall’s installation on the studs. You can be able to pull back the wires to an intermediate or a starting point – another electrical box in the direction of the electric service panel.

In that case, there is a possibility of striping the electrical wires toward the up-line electrical box and then using it as your termination point. That will save you from the trouble of buying an extra electrical box with capped electrical wires and blank wall plates.

Another feasible option is to strip back the electrical wires to their original starting point – the circuit breaker on the service panel. It is only possible for a whole house to remodel where the drywall has been removed. (2)

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References
(1) aesthetic – https://www.britannica.com/topic/aesthetics
(2) feasible option – https://www.indeed.com/career-advice/career-development/how-to-write-feasibility-studies

About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gI realized early on carpentry was a huge passion for me and I’ve stayed in the industry for over 20 years now. This gives me a unique ability to really be able to tell you what the best tools and recommendations are. I’m not only a carpenter but I also like machinery and anything to do with electrics. One of my career paths starting off was as an apprentice electrician so I also have a lot of experience with electrical products and anything related.