How to Safely Divert Power from One Circuit to Another Without Rewiring Your Whole House

Introduction

I often find myself needing more outlets or circuits in certain rooms of my house, but I don't want to undergo the expense and mess of rewiring my whole house. Thankfully, there are some safe methods I can use to divert power from one existing circuit to another without a major rewiring project. In this article, I will walk through the steps I take to safely add a new circuit by tapping into an existing one.

Things to Know Before Getting Started

Before I start any electrical project, there are some important safety issues I need to consider:

Electrical safety - Working with household electrical wires can be extremely dangerous if proper precautions are not taken. I always make sure to turn off the relevant circuit breaker before doing any work. I also use appropriate personal protective equipment like insulated gloves and eye protection.
Electrical codes - Most jurisdictions require that any electrical work be done to code. I always check my local regulations before taking on a project. Common requirements include proper wire gauges, junction boxes, conduit, and more. Trying to cut corners could make for an unsafe installation.
Circuit capacity - I need to make sure the existing circuit I plan to tap into has sufficient capacity to support the additional load I will be placing on it. Overloading a circuit can lead to nuisance tripping of the breaker or, in a worst-case scenario, a fire hazard.

How to Tap Into an Existing Circuit

With the proper background knowledge and safety precautions, I am ready to tap into an existing 120V household circuit to add an additional outlet. Here is the process I follow:

I turn off the circuit breaker supplying the existing circuit I want to tap into. I double check that the power is off using a non-contact voltage tester. Safety first!
I remove the cover plate from the existing outlet I want to use as my connection point. I unscrew the outlet from the electrical box but leave all the wires connected.
I plan the new outlet location. I may need to drill holes through walls/floors to run the new wiring from the existing outlet to the new one. I take care to avoid contact with any hazards like plumbing lines during this step.
I feed a length of 12 AWG or 14 AWG copper wire from the new outlet location back to the existing outlet electrical box. The gauge depends on the length of the wire run and how much current will flow through it.
I connect the new wire to the existing outlet wires using wire nuts. The black goes with the other hot wires, white with neutral, ground with ground. This parallels the new outlet into the existing circuit.
I securely mount the new outlet into its electrical box, screw it in place, and attach the cover plate.
Lastly, I turn the circuit breaker back on and test that the new outlet works as expected. I can now plug in and safely use the new outlet!

Important Notes on Electrical Safety

When tapping into existing household circuits, I keep the following safety guidelines in mind:

Use caution when working in electrical boxes - live wires can still be dangerous, even when the circuit is turned "off." I always double check with a voltage tester.
Only use wiring properly rated for the amperage of the circuit. Undersized wiring can overheat. I use 12 AWG for 20A circuits and 14 AWG for 15A circuits.
Follow code requirements for cable types, junction boxes, conduit, grounding, and other safety factors. I check with my local building department if I am unsure.
Be organized - I neatly route and secure all new wiring. Exposed or tangled wires pose safety risks.
Label new circuits at the breaker panel. This avoids confusion down the road.
Consider whole-home surge protection. Adding circuits can increase susceptibility to electrical surges. Proper surge protection helps safeguard my home's electrical system.

In Closing

With proper preparation and by following basic safety precautions, tapping into existing circuits can be a doable project for a knowledgeable DIYer. I am now able to use this technique to expand the outlets and circuits in my home without undertaking major rewiring. However, I know my limits and will call in a licensed electrician for any complex or high-voltage work. Do you have any other tips for safely adding new circuits in my home? Let me know!