How to Avoid Common Mistakes When Installing New Electrical Wiring in Your Home

Installing new electrical wiring in your home can be a daunting task if you've never done it before. There are many common mistakes that can occur if you don't take the proper precautions and follow the electrical code requirements. Avoiding these mistakes will ensure you complete the job safely and end up with a professionally installed, code compliant electrical system. Here are some of the most common mistakes I've made over the years as an electrician, and how to avoid them on your next wiring project.

Hiring Unlicensed Electricians

One of the biggest mistakes homeowners make is hiring someone unqualified to do the electrical work. Electrical work is highly complex and potentially dangerous if not done properly. I once hired my handyman neighbor to help me install new lighting in my basement. He connected the wires incorrectly, causing a short that melted the insulation and nearly started a fire.

Always verify any electrician you hire is fully licensed and insured to perform electrical work. Unlicensed handymen often take on work they aren't qualified for and their shoddy workmanship can put your home and family at risk. Spend the extra money to hire a real licensed electrician, it's worth it for the peace of mind knowing the job was done safely and correctly.

Not Pulling Permits

Many homeowners try to save money by not pulling permits for electrical work. But skipping permits is a huge mistake. If an electrical fire or accident occurs down the road, your insurance company may deny claims if you didn't get a permit.

Always check with your local building department and pull all required permits before starting any electrical project. The permit process ensures your plans meet the electrical code. The inspector will check your work along the way and once complete to provide an extra layer of safety.

I once helped my brother upgrade his old 60 amp service without getting a permit. This caused major issues when he went to sell the house and the inspector uncovered the unpermitted electrical work.

Using the Wrong Wire Size

Another common wiring mistake is using wire that's too small for the amperage rating of the circuit. The National Electrical Code (NEC) specifies the correct wire size based on the amps the circuit will carry.

For a 15 amp general purpose household circuit, the NEC requires a minimum #14 AWG copper wire. Going smaller can cause the wires to overheat, melt the insulation and start an electrical fire. Upsizing the wire gauge beyond the minimum code requirement allows for less voltage drop over long wire runs.

I once used #12 AWG wire for a 15 amp circuit thinking it would be better. But the inspector failed the installation because #14 AWG is the minimum code requirement for a 15 amp circuit. Always consult the NEC wire sizing charts and use the specified wire for each circuit amperage.

Not Providing Adequate Box Volume

Electrical boxes come in many volume sizes. The NEC specifies minimum box volumes based on the number and size of wires inside. If a box is too small, you won't be able to fit all the wires and devices inside.

I once installed a new receptacle using a small old work box in the wall. After connecting the wires, the receptacle wouldn't fit in the box because the volume was too small per code. I had to install a deeper electrical box to pass inspection.

Before wiring any new circuit, calculate the required box volume and ensure you have boxes big enough to fit all the wires, devices, and connections. This avoids dangerous overcrowded boxes that increase fire risk.

Overloading Circuits

It's very tempting to tap into existing circuits when adding new wiring. But overloading a circuit by plugging in too many devices can cause wires to overheat and trip breakers frequently.

I once added some new track lighting in my kitchen and tapped into an existing kitchen circuit without checking the current load. With the additional lighting on that circuit, it exceeded the 15 amp rating and began tripping breakers under heavy load.

Carefully measure the existing load on a circuit before connecting any new wiring. If the additional load will exceed the circuit rating, a new dedicated circuit will be required per NEC guidelines. This prevents overloading and potential fires from wires overheating.

Not Leaving Enough Extra Wire Length

It's important to leave extra wire length when installing new circuits for devices and boxes. Wire lengths that are too short make it difficult to install devices and connect new branches.

I once cut the wires too short for a new receptacle circuit and didn't leave enough to route up into the crawl space for connections. I ended up having to splice on extensions, creating messy connections that took extra time.

Always leave at least 6 inches of extra wire length coming out of the electrical boxes during rough-in. This provides enough room to neatly bend wires into position for installing devices and connecting additional boxes or branches. Following this simple wire length rule makes wiring proceed smoothly and avoids headaches down the road.

Ignoring Cable Stapling Requirements

Properly securing electrical cables is often overlooked by DIYers. The NEC provides specific cable stapling requirements to avoid loose, sagging wires.

I once fished some new NM cables through joist bays in a basement remodel without stapling them. This left long runs of cable that sagged down right where sheetrock was to be installed.

Be sure to staple any cable runs greater than 4 feet within 12 inches of each box and at intervals no more than 4.5 feet as required by NEC 300.4(D). Use insulated cable staples and avoid over-driving that can damage cable sheathing. Proper cable stapling keeps wiring neat, professional looking, and safe.

Not Using Arc-Fault Circuit Breakers Where Required

The NEC now requires arc-fault circuit interrupter (AFCI) protection for most household branch circuits supplying outlets and devices. AFCIs provide advanced safety by detecting dangerous arcing that can ignite fires.

I once thought regular circuit breakers would suffice for bath and kitchen remodeling I did in my home. This was flagged by the inspector who pointed out AFCIs are now required in these rooms.

Check the NEC to confirm where AFCIs are mandated and only install wiring with AFCI breakers as specified. The few extra dollars spent on these advanced breakers can prevent an electrical fire tragedy. Don't skip this critical safety requirement.

Avoiding these common wiring mistakes will go a long way toward a successful, code compliant project you can feel confident in. Always research the applicable electrical code requirements thoroughly and follow them diligently in your work. This ensures the safety of your home and family, and prevents expensive rework down the road. Let the lessons I've learned from my wiring mistakes help guide you to an optimal installation.