How to Wire a 200 Amp Electrical Service for an Older Home

Introduction

Upgrading the electrical service in an older home to 200 amps can provide the power needed to run modern appliances and electronics. However, working with electrical wiring carries risks and should only be done by qualified professionals. This article will walk through the end-to-end process I follow when wiring a 200 amp service for an older home.

Gather Materials and Tools

The first step is ensuring I have all the necessary materials and tools:

• 200 amp electrical panel - This will have enough spaces and amperage capacity for circuits in a modern home. I prefer square D or Eaton panels.

• Appropriately sized wire - For a 200 amp service, I use 2/0 AWG copper wire with THHN insulation for the feeders and 1 AWG for the ground.

• Conduit and fittings - EMT metal conduit with all necessary clamps, connectors, straps, elbows, and bushings to run a safe and code compliant install.

• Breakers - I make sure to have enough full-size breakers for all planned circuits, including spares for future expansion.

• Safety gear - Non-conductive gloves, glasses, hard hat, and boots. Proper safety gear can prevent severe injuries.

• Voltmeter - For safely testing voltages to confirm power is off.

• Cable cutters, strippers, crimpers - For preparing and joining wires.

• Hammer drill and bits - To drill holes through framing for running conduit.

• Ladder - For access to the overhead service entrance location.

Inspecting the Current Setup

Before getting started, I'll thoroughly inspect the existing electrical service to understand the current setup and see if anything can be reused. Key things I'll look for are:

• The location of the service entrance and meter.

• The size of the existing service panel and main breaker amperage.

• If there is existing unused space in the service panel.

• The gauge and type of wiring used.

• Any deficiencies like aluminum wiring or knob and tube wiring.

• The grounding method used and condition of ground wires and rods.

Taking detailed notes on the existing setup saves time and helps me determine what materials I'll need.

Killing the Power

Before touching any wiring, I fully de-energize the system by:

• Turning off the main breaker in the service panel.

• Disconnecting the service entrance wires from the service panel.

• Removing the meter from the meter base if possible.

• Testing voltages with a voltmeter to confirm power is off.

I also turn off the water main when working around electrical panels to be extra safe. I keep the system de-energized by tagging out the main breaker while I work.

Running New Service Entry Conduit

I start by marking a path to run rigid metal conduit from the planned panel location to the service entrance:

• I choose the shortest and straightest route possible.

• I ensure I can maintain proper conduit bend radius.

• Holes are drilled through framing using a hammer drill.

Once the path is ready, I thread and connect the conduit segments:

• EMT conduit with set screw connectors are used.

• I avoid too many couplings to limit points of connection failure.

• Conduit is secured tightly using clamps.

Installing the New Panel

With the conduit in place, I'm ready to mount and wire up the new 200 amp panel:

• A permitting inspection may be required before covering the panel.

• I match the mounting height to the existing panel, typically 4-5 feet from ground.

• At least 1 inch of space is left on all sides for ventilation.

• The panel is placed close to the entrance conduit but still accessible.

• I carefully level and plumb the panel to ensure breakers fit properly.

• Anti-oxidant compound is used at all aluminum wire terminations.

Running and Landing the Feeder Wires

Now I can pull and connect the feeder wires from the service entrance to the new panel:

• 2/0 AWG THHN copper wires are used for the two 120V hot feeders.

• A 1 AWG bare copper wire is pulled for the ground.

• Wires are carefully pulled to avoid damage to insulation.

• 6 inches of extra wire are left at both ends for connections.

• The ground is connected to the ground bus bar in the panel.

• The neutral and hot wires are landed on their correct breaker lugs.

Installing the Grounding Electrode System

A proper grounding electrode system is crucial for safety and performance. I install new ground rods and a ground wire:

• One ground rod is driven 8 feet into the ground for each 200 amps of service.

• The ground rods are connected via 6 AWG bare copper wire.

• The wire is protected where it comes above ground.

• Ground wires are connected to the ground bus bar and bonded to panels.

• All metal water lines are bonded to the grounding system.

Connecting at the Service Entrance

With everything prepped, it's time to connect up the service entrance:

• The utility provider is contacted to inspect or make the connections.

• Hot, neutral, and ground are landed on the correct terminals.

• Once connected, I apply weatherproofing.

• The meter is re-installed and sealed.

• All covers are replaced to prevent accidental contact.

Wrapping Up

Once all connections are made, I'm ready to energize the new panel:

• With panels closed, the main breaker is turned on.

• Voltages are verified at the panel before closing it up.

• I check for proper voltage at outlets throughout the house.

• The old panel and unused wires are removed.

• Insulation is restored and all holes patched up.

• Permits are signed off on final inspection.

Wiring a 200 amp service requires attention to detail and adherence to electrical code and safety practices. Following these steps helps ensure I complete a safe, future-proof electrical upgrade. Let me know if you need any electrical work done!