How to Wire Outlets in an Old Home

Wiring outlets in an old home can seem daunting, but with proper planning and safety precautions, it is very doable. Here is a comprehensive guide on how I go about wiring outlets in old homes:

Assess the Existing Electrical System

Before beginning any electrical work, it's crucial that I thoroughly examine the existing electrical system. Here are the key things I look out for:

Check the Electrical Panel

• I open up the electrical panel and check the branch circuits to see how the existing outlets are wired. This gives me an idea of the current amperage and wire gauge used.

• I also check if there are any open breaker slots to add new circuits. If not, I may need to upgrade the panel.

Look for Older Wire Types

• In really old homes, I may encounter old knob and tube wiring. This needs to be replaced completely before adding any new wiring.

• Cloth-covered wiring was also commonly used in older homes. I check its condition closely before reusing any of it.

Examine Existing Outlets and Fixtures

• I remove a few existing outlets/light fixtures and examine the condition of the wiring. Brittle, cracked, or fraying wire insulation indicates wiring that needs replacement.

• I also check if any outlets are ungrounded 2-prong models, which will need upgrading.

Develop a Wiring Plan

Once I've assessed the existing system, I develop a detailed plan for the new outlet wiring:

Choose Locations Wisely

• I determine optimal new outlet locations based on furniture placements and devices needing power.

• I also consider how the outlets will be used - a kitchen counter outlet needs to be placed differently than a living room outlet.

Calculate Electrical Loads

• I add up the wattages of devices that will be powered from each new outlet. This determines the required circuit amperage.

• For any high draw appliances like a refrigerator or window AC unit, I install dedicated 20 amp circuits.

Select Suitable Wire Gauge

• Based on the required amperage and wire run length, I select the appropriate wire gauge. For 15/20 amp circuits this is usually 14 gauge.

• I may need a heavier 12 gauge wire if the wire run to the new outlet is very long.

Plan Circuit Layouts

• I determine whether to power the new outlets from existing circuits, or run new circuit wires from the panel.

• I draw up circuit layouts to plan the exact wiring runs to each new outlet.

Install New Outlet Boxes

With the wiring plan complete, I'm ready to start the installation:

Cut Openings for Old Work Boxes

• For existing walls, I use old work boxes with built-in clamps. I measure and cut open rectangular holes for these boxes.

• I take care not to cut the holes too big - the boxes should fit snugly when squeezed into the holes.

Mount New Outlet Boxes

• I slide the cables into each old work box, then squeeze the box into the opening until the clamps tighten on the drywall. This secures the box firmly.

• For new walls, I mount new work boxes before insulation and drywall. I carefully position them and nail them directly to wall studs.

Allow Slack in Wiring

• When installing the boxes, I ensure the wires have at least 6 to 8 inches of slack. This makes it easier to connect the outlets later.

Run and Connect Outlet Wiring

With the boxes installed, it's time to run and terminate the new wiring:

Choose Appropriate Cabling

• For 15/20 amp branch circuits, I use 14/2 NM cable with ground. I match the cable size to the circuit amperage.

• For longer wire runs I may use 12/2 NM cable for lower voltage drop. I stick to copper wire for safety and efficiency.

Route Cables to Outlet Boxes

• I carefully run the cabling from the panel to each outlet box, following the layout plans. I leave ample wire at the ends for connections.

• For finished walls, I fish NM cables down from the attic or up from the basement. I use wire lubricant to pull cables through.

Allow Slack at Outlet Boxes

• At each box, I again ensure I've left 6 to 8 inches of extra cable. This makes it easy to manipulate the wires for terminations.

Connect Wires Securely

• I strip 5/8" insulation from the wire ends and connect them securely to the outlets with screw terminals. I ensure tight connections.

• I wrap connections with electrical tape for additional insulation. The black wire connects to the brass screw, white to silver.

Finish Up and Test

Once all the outlets are wired up, I'm ready to finish the job:

Cap Off Unused Wires

• For any unused circuit wires, I cap them off individually with wire nuts to prevent contact. Proper insulation is critical.

Secure Cables Clamp

• I neatly fold and organize the wires into the boxes, then tighten the cable clamps securely. This prevents strain on connections.

Attach Outlet to Box

• With the wiring complete, I screw the outlet into the box. For a neat finish, I ensure outlet screws align vertically.

Test Each New Outlet

• Before closing up, I test each new outlet for power with a multimeter or outlet tester. I confirm proper grounding and polarity.

Label Circuits at Panel

• At the panel, I label the new circuit wires with adhesive tags. This makes it clear which outlets are powered from each circuit.

With good planning, safe methods, and testing, I'm able to successfully install new solid, safe outlets to expand power in any old home. The improved convenience is well worth the effort!