How to Safely Rewire Your Home Electrical System Yourself

Introduction

Rewiring the electrical system in your home can seem like a daunting task, but with proper planning and precautions, it can be done safely without the need to hire an electrician. Electrical work does require attention to detail and adherence to electrical codes and safety standards, but the process itself is straightforward. In this guide, I will walk you step-by-step through everything you need to know to successfully rewire your home's electrical system yourself.

Reasons For Rewiring

There are several common reasons you may need or want to rewire your home's electrical system:

• Upgrading the service - If your home's electrical needs have increased, you may need to upgrade the amperage of your electrical service. This requires running new wire from the main panel to the utility company's transformers.

• Replacing old wiring - If your home's wiring is very old, it's a good idea to replace it to prevent hazards from outdated, damaged wiring. Old wiring is often not up to current code standards.

• Remodeling needs - Any major remodeling project will likely require some rewiring to accommodate demolished walls, relocated plumbing and HVAC, and new room layouts.

• Safety concerns - If your existing wiring frequently trips breakers, experiences voltage drops, overheats, or shows other safety issues, a rewire is in order.

• Efficiency upgrade - Newer wiring is more energy efficient. Upgrading allows you to reduce waste and save on electric bills.

No matter the reason, a complete rewire has the benefit of bringing your home's electrical system fully up to modern safety and performance standards.

Electrical Load Calculation

The first step in planning your rewire is to calculate your home's electrical load. This determines how much amperage you'll need from your electrical service.

To calculate load:

• Make a list of all electrical devices and lights in the home. For lights, note the wattage of each bulb.

• Lookup the wattage or amp rating for each device and record it.

• Categorize each item as either a continuous load (refrigerator, electronics on standby) or intermittent load (window AC unit, microwave).

• Multiply the wattage of continuous loads by 125% to compensate for inrush current.

• Add up the loads for each category.

• Refer to your utility's guidelines for required spare and future capacity.

• Add all load types together, then pick a service amperage at least 20% above the total.

This gives you the minimum service capacity needed to handle your home's electrical needs.

Evaluating Your Existing Electrical System

Before developing a rewiring plan, you need to thoroughly evaluate your existing electrical system:

• Service entry wires - Note the gauge and insulation type of the wires running from your main panel to the outside service mast. This determines how much amperage they can safely handle.

• Main service panel - Check the amp rating of your main breaker or fuse panel. This is the maximum capacity of your existing service.

• Voltage - Most homes have 120/240-volt electrical service. Multifamily dwellings sometimes have 208/120-volt. Voltage affects your wiring needs.

• Grounding - Inspect ground wires and rods. These safety systems must be intact and up to code.

• Branch circuits - Evaluate the number and ampacity of your existing circuits. Add up the breaker/fuse sizes to determine capacity.

• Wire gauge - Note the gauge wire used for circuits. This determines how much current they can handle based on length.

• Wiring method - Determine if you have armored cable, non-metallic cable, conduit, or knob and tube wiring.

With this information in hand, you can begin mapping out an optimal rewiring plan tailored to your home.

Developing a Rewiring Plan

Your rewiring plan serves as a roadmap for the project. It should include:

• Service size - Specify the amperage based on your load calculation and expected future needs.

• Main panel location - Note where you'll install the new main service panel for optimal access.

• Subpanel locations - Determine locations for any new subpanels, if needed, based on home layout.

• Circuit mapping - Indicate which rooms and devices will be served by each new circuit. Include circuit types, purposes, and ampacity.

• Wiring routes - Map out how you'll run wiring through walls, floors, and ceilings to feed devices and lights on each circuit.

• Grounding/bonding - Design proper grounding and bonding for safety. Show connection points and ground rod locations.

• Smoke/CO detectors - Include locations for all detectors as required by code.

• Schedule - Create a project schedule outlining the order in which you'll tackle each stage of the rewiring project.

Take the time to carefully think through all aspects of the rewiring to create a solid plan before purchasing any materials or starting work.

Electrical Codes and Permits

Electrical work must adhere to national, state, and local electrical codes for safety. These include standards like the National Electrical Code (NEC). Thoroughly research the applicable codes in your area.

Most areas require permits and inspections for electrical service upgrades and rewiring projects. Contact your local building department early in the planning process to learn about permit needs, inspection requirements, and scheduling.

Some key NEC requirements include:

• Only using approved wiring methods like NM cable in dry areas and conduit for exposed areas
• Proper sizing of wires based on ampacity and load
• Using GFCI protection where required
• Having enough circuits to avoid overloading
• Maintaining minimum working clearances around panels and equipment

Closely following code ensures your DIY rewiring project meets all safety standards. Failing inspections can lead to significant delays and added costs.

Purchasing Materials and Equipment

Based on your rewiring plan, you'll need to purchase:

• Wire - For power circuits, use THHN/THWN-2 copper wire rated for 75°C minimum. Size wires based on load and circuit length.

• Conduit - Use rigid galvanized or EMT conduit where wiring is exposed. Match diameter to wire size.

• Boxes - Use steel junction boxes for connections. Size to number of wires and devices.

• Panels - Choose main and subpanels rated for your service size calculated earlier.

• Breakers - Get listed circuit breakers matching your panel manufacturer. Follow code for type and amperage.

• GFCIs/AFCIs - Purchase ground fault and arc fault circuit interrupters as required by code.

• Lights and devices - Buy devices like receptacles, switches, and light fixtures called for in your rewiring plan.

Shop at reputable electrical supply stores to ensure everything meets NEC and local code standards. Stick closely to your rewiring plan and code requirements.

Safety Gear and Equipment

Rewiring a home comes with electrical hazards. Have the proper safety gear:

• Voltage tester - Test wires to confirm power is off before working.

• Insulated tools - Use screwdrivers, cutters, and crimpers rated for electrical work.

• Fish tape - Use non-conductive fish tapes to run wires through walls and ceilings.

• Ladder - Have a sturdy fiberglass ladder for working on ceilings and upper walls.

• LED work lights - Provide movable task lighting as you work in boxes and panels.

• Multimeter - Use to measure voltage, current, and continuity.

• Personal protective equipment:

• Rubber-soled non-conductive shoes

• Insulated gloves rated for the voltage you are working on
• Safety glasses
• Face shield for electrical enclosures

With the proper safety equipment, you can perform a rewire safely without risk of shock or arc flash.

Working With the Power Off

A key safety rule is to always work on electrical wiring with the power turned completely OFF. To do this:

• Shut off the main breaker and verify power is off with a voltage tester.

• Then disconnect the power at the service drop before starting any work on service entrance wires.

• Only reconnect your main breaker and turn power back on when the new service installation is 100% complete.

• For other circuit work, shut off power at the breaker and lock it off so it can't be turned on accidentally.

• Always double check wires with a voltage tester right before working to confirm they are dead.

Taking these precautions prevents shock or electrocution hazards. Be diligent about keeping the power off throughout your entire DIY rewiring project.

Running and Securing New Wires

Here are some best practices as you run new wiring:

• Carefully measure wire runs and cut them to length with extra slack before pulling. Don't splice mid-run.

• Use chase holes or cut access holes between studs to route wires vertically and horizontally.

• Staple cables every 4-1/2 feet and within 8 inches of boxes per NEC. Stagger staples when running multiple cables.

• Use metal nail plates to protect wires from drywall screws or nails.

• Pull NM cables through holes and around obstacles carefully to avoid kinks or damage to the insulation.

• Seal around wires with fireblock caulk where they penetrate firewalls.

Taking the time to properly install and secure wires makes for a long-lasting rewire.

Making Safe Connections

Follow these guidelines when making wire connections:

• Use listed wire nuts or crimp connectors sized for the number and gauge of conductors.

• Twist wires together clockwise before capping with a nut.

• Make tight connections and tug test each one. Loose connections can arc and overheat.

• Stagger splices across multiple wires to minimize bulge in boxes.

• Use terminal blocks in panels and junction boxes with many wires.

• Wrap splices with electrical tape for protection.

Properly spliced connections ensure good continuity and prevent shorts or arcs when energized.

Testing and Energizing the System

Once the new wiring installation is complete, it's time to test and energize. Proceed methodically and safely:

• Perform continuity tests on all circuits to ensure no open wires.

• Use a megohmmeter to perform insulation resistance testing between conductors, and between conductors and ground. Ensure no shorts are present.

• Visually verify all neutral and ground wires are properly landed. Double check breakers are sized correctly.

• Replace all covers on boxes and panels before energizing.

• Turn on power at the main breaker and methodically test outlets, lights, and devices on each circuit.

• Use an ammeter to verify balanced load across multiwire branch circuits.

• Allow inspection as required by the AHJ before covering any work.

Thorough testing confirms safe and good connections throughout the system. Your DIY rewire is now complete!

Conclusion

While rewiring a home is a major project, it can be successfully accomplished DIY. Careful planning, adhering to electrical codes, using proper materials and safety gear, and methodical installation and testing steps allow you to upgrade your electrical service and wiring safely and economically. Paying close attention to detail ensures your rewired home electrical system will function flawlessly for years to come.