Here's what to look for, and how to fix what you find.
15 Electrical Mistakes Homeowners Make
Updated on Sep. 19, 2024
Working on your own home is empowering, and it saves you money. Even before I became an electrician, I tackled DIY projects from plumbing to painting to carpentry. Electrical projects require a special level of precaution, though, because just a few milliamps of current can be deadly. You can do this, though. To help, I talked to two experienced electricians to walk through these top 15 electrical mistakes to avoid.
Below, find out what to look for, and how to fix what you find.
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Using a Non-Contact Voltage Tester Incorrectly
Mistake: Misusing your tester.
Electricians always carry non-contact voltage testers with them, and you should have one, too. They’re inexpensive and easy to use, and they help keep you safe when doing DIY electrical work.
Solution: Test. Use. Verify.
First, test the tester by holding it to a known live circuit, like a powered appliance or lamp cord. Or, insert it into a receptacle (use the smaller slot, which is the hot side). The tester should light up and/or beep. Locate the circuit you’ll be working on and turn off the breaker. Use the tester to verify the circuit’s off, then check the tester on the same live circuit as before to confirm it functioned correctly.
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Making Connections Outside Electrical Boxes
Mistake: Not using an electrical box.
“Electrical boxes, sometimes referred to as junction boxes, protect connections from accidental damage, and help contain sparks and heat from a loose connection or short circuit,” says Gerald Talbot, licensed electrician with Mister Sparky. “Failing to make connections inside the electrical box is arguably the biggest mistake a homeowner can make, as this can result in major hazards.”
Solution: Add a box.
If you start a project and find a jumble of taped-together wires stuffed in the wall cavity instead of neatly contained in a junction box, don’t ignore it. (This happened to me, with a century-old knob and tube wiring.) Ensure the power is off, add a box and reconnect the conductors. If you’re not near a stud, use “old work” remodel boxes that grip right to the drywall.
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Cutting Wires Too Short
Mistake: Too-short wires
Trying to join, aka splice, tiny little wires in an electrical box is tough. “Short wires can cause a host of potential hazards and make connections difficult,” Talbot says. Bad splices can cause electrical arcs and fires, so the National Electrical Code (NEC) requires six inches of free conductor at every electrical box. Over time, though, conductors tend to get shorter as people swap out devices over the life of a home.
Solution: Add pigtails
If you open up an electrical box to find stubby conductors, add pigtails, which are short pieces of wire used to extend electrical connections. Of course, you still have the problem of splicing the pigtails onto the tiny conductors. To make things easier, use push-in connectors or lever nuts, aka Wagos, rather than trying to spin on a traditional wire nut.
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Backstabbing Instead of Using Screw Terminals
Mistake: Backstabbing electrical connections
Receptacles and light switches have holes where you can insert the conductors instead of attaching them to the terminal screws. “Backstabbing” is technically acceptable (after all, the holes are right there), but the connections tend to loosen over time, potentially causing electrical arcs and fires.
Solution: Use the screw terminals.
Every electrician I’ve ever met (including me) prefers using the terminal screws, or pigtailing to them, instead of backstabbing. Make a hook on the end of the conductor and wrap clockwise around the terminal screw. Tighten with a screwdriver.
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Reversing Hot and Neutral
Mistake: Reversing hot and neutral
This creates a shock hazard, and because the light or device will likely still work, you won’t even know it until it’s too late.
Solution: Identify wires and terminals
In a standard NM-B cable, the black wire is the hot, the white is the neutral and the bare copper wire is the equipment grounding conductor (EGC). When wiring receptacles and light switches, attach the black wire to the brass screw (labeled HOT), and the white wire to the silver screw (labeled WHITE). The bare ECG goes to the green ground screw.
For wires that aren’t clearly marked by color, like on a lamp cord, the hot is the smooth wire, and the neutral has ribs, grooves or other markings.
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Installing Cable Without a Clamp
Mistake: Missing cable clamp
I can’t tell you how often I’ve found NM-B (Romex) cable resting, or pulled taut, against the sharp edges of a metal electrical box. Over time, this friction point wears down the insulation and is a major fire hazard.
Solution: Use a cable clamp.
“When using metal junction boxes, it is important to use a cable clamp to ensure the cable is securely fastened within the box and conductors will not get exposed outside of the box,” says Chris Lozano, master electrician and virtual electrical expert at Frontdoor. Make sure the clamp is secure around the cable, Lozano says, but don’t crank down too much to avoid constricting the wires.
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Using the Wrong Size Conductors
Mistake: Choosing the wrong wire size.
Electrical conductors’ diameter, or gauge, determines how much current they can safely carry. Using too-small wires causes overheating, but unnecessarily large wires are a waste of money.
Solution: Match existing conductors.
When doing DIY electrical work, check the size of the breaker and match the existing wire in the box. Most of the time, you’ll see 14-gauge conductors on 15-amp circuits, and 12-gauge wire on 20-amp circuits. It’s okay to have bigger wires than necessary, but never go smaller.
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Replacing Two-Slot Receptacles
Mistake: Incorrectly replacing two-slot receptacles
Two-slot receptacles have hot and neutral connections only. If you have a three-prong, grounded plug, you’re out of luck. Removing the ground prong, using an adapter or swapping out a two-slot for a three-slot receptacle are major electrical mistakes to avoid.
Solution: Swap out two-prong for GFCI
The quickest way to make the outlet safer is to add a ground-fault circuit interrupter (GFCI). The circuit still won’t be grounded, but the device will provide shock protection. You can plug in a three-prong plug, and it’s an NEC-approved replacement option. Label the front of the GFCI “No Equipment Ground.” (There are stickers in the GFCI box for this purpose.)
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Recessing Boxes Behind Wall Surfaces
Mistake: Exposed combustible material
“When boxes are set too far into the wall, it creates safety hazards and fire risks, plus the unit is less accessible,” Talbot says. In tile, drywall and other noncombustible materials, boxes can sit back one-quarter of an inch, while they must be exactly flush with the surface of wood paneling and other flammable walls.
Solution: Add a box extender
Box extenders are cheap, handy tools used “to extend a box past a certain depth, like when backsplash tile is installed on a kitchen countertop,” Lozano says. They’re easy to install, and you don’t even have to dismantle the device. (But always turn off the power!) Just slip it over the switch or receptacle and secure it to the existing box.
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Upsizing Breaker Without Updating Wire
Mistake: Swapping out a breaker without updating conductors
A breaker that constantly trips is trying to tell you something. You’re putting too much load on the circuit, or the wiring has a problem. If you’re tempted to swap out the breaker for a bigger one to stop the tripping, don’t. Upsizing the breaker doesn’t diagnose your wiring problem, and the old wires will be too small for the new breaker.
Solution: Call a licensed electrician.
Hire a licensed electrician for matters concerning your electrical panel unless you really know what you’re doing.
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Installing Ceiling Fan In the Wrong Box
Mistake: Undersizing ceiling fan box
Before I was an electrician, I had a comically bad experience attempting to install a ceiling fan. The main problem? The ancient electrical box in the ceiling was not designed for the weight of the fan. Ceiling fans are heavy, and they rotate. They need to be properly supported.
Solution: Get the right box.
If your fan is 35 pounds or more, it must be supported by a listed box that is marked with the weight the box can support. If the box is not marked, a ceiling joist or other structural member must independently support the ceiling fan. If your fan is over 70 pounds, it must be supported independently no matter what.
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Overfilling Electrical Boxes
Mistake: Too many wires in a junction box.
Stuffing as many wires as possible into an electrical box is a fire hazard.
Solution: Follow box fill requirements.
The NEC limits the number of wires, devices, clamps and other accessories inside electrical boxes. This code requirement is called “box fill,” and it’s based on volume. Each item is assigned a value based on the gauge of the wire inside the box, and when added together, they must be less than the box’s volume.
The NEC occasionally updates box fill requirements, so check with your local code authority to know which ones to follow. It’s also perfectly acceptable to buy bigger boxes than you technically need. Future electricians will thank you.
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Using Too Many GFCIs and AFCIs
Mistake: Buying too many expensive devices
The NEC requires GFCI and/or arc fault current interrupter (AFCI) protection in most places in your home. But, that doesn’t mean you have to buy dozens of GFCI and AFCI receptacles to install in every outlet. That’s good, because they’re expensive.
Solution: Use one receptacle to protect an entire circuit.
GFCI and AFCI receptacles have two sets of terminals: Line and Load. The power comes into the line side, and the load side connects to the next receptacle. As long as you daisy-chain the rest of the circuit, a single GFCI or AFCI, or a combo, will protect the receptacles downstream (which can be regular receptacles).
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Overloading Electrical Circuits
Mistake: Too many devices on one circuit
“An overloaded circuit can lead to device and wire failure, which can ultimately lead to fire and destruction of equipment,” Lozano says.
Solution: Keep things separate
If you’re roughing in a new addition or trying to decide whether a circuit can handle another appliance, err on the side of caution. “Things like window AC units, space heaters, microwaves, and other appliances can be a huge draw, so it is best to keep them separate or run dedicated circuits when possible,” Lozano says.
A 15-amp circuit can handle 1800 watts, a 20 amp circuit 2400 watts. Look at the amps or watts listed on your appliances and devices, and add them up. (To convert amps to watts, multiply amps by 120 volts. To find amps from watts, divide watts by 120 volts.)
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Not Calling a Licensed Electrician
Mistake: Getting in over your head.
DIY electrical work can be very rewarding and save you money. But it’s different from fixing a leaky pipe. It only takes a few milliamps of electricity to cause severe injury and even death.
Solution: Don’t mess around with your safety.
If you find yourself in a situation where you’re uncomfortable, stop. Have a licensed electrician investigate frequently tripping breakers, flickering lights, burning smells, scorch marks or melted devices. Always turn off the power (and verify it’s off) before looking into anything yourself.
About the Experts
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- Chris Lozano is a master electrician and virtual electrical expert at Frontdoor, a home care and maintenance app that connects people and professional technicians via tech-enhanced video chats. Lozano has more than ten years of experience in the electrical industry.
- Gerald Talbot is a licensed electrician with Mister Sparky. Talbot has electrical contracting licenses in Georgia and Tennessee and is the owner-operator of Mister Sparky in Chattanooga, Tennessee.
