How to Wire a 200-Amp Main Electrical Panel

Table of contents

1. Safety, scope, and code

2. Tools and materials

3. Panel selection and placement

4. Mounting the panel

5. Bringing in the service entrance cable (SE/U or equivalent)

6. Bonding and grounding (ground rods & electrode conductor)

7. Preparing for homeruns (cable management & knockouts)

8. Terminating branch circuits

9. Installing breakers: standard, double-pole, AFCI/GFCI

10. Feeding a future subpanel (100-amp example)

11. Dressing the panel, covers, and labeling

12. Pre-inspection checklist

13. Frequently asked questions

1) Safety, scope, and code

• De-energize everything before working. Assume conductors are live until proven otherwise with an appropriate meter.

• Follow your local code. The NEC is widely adopted in the U.S., but local amendments and utility requirements vary. Permits and inspections are typically required.

• Working room: Maintain clear working space in front of the panel (commonly 30 in. wide × 36 in. deep × 6 ft 6 in. height).

• Panel height: The topmost breaker handle typically must not be higher than 6 ft 7 in. above the floor (verify locally).

2) Tools and materials

Tools

• Stud finder, level, and tape measure

• Laser level or chalk line (for height and alignment)

• Screwdrivers (square, Phillips, slotted), nut drivers

• Lineman’s pliers, needle-nose pliers, side cutters

• Aviation/tin snips, utility knife

• Knockout set or punch; step-bit as needed

• Wire strippers (sized for copper/aluminum gauges used)

• Torque driver/wrench for terminations (follow torque specs)

• Hammer drill/driver and appropriate fasteners

• Multimeter / voltage tester

• Personal protection: safety glasses, gloves

Materials

• 200-amp, 40-space/80-circuit plug-on neutral load center (e.g., Square D Homeline or comparable)

• Main lugs covers (often included), bonding screw/strap (for service equipment only)

• SE/U or utility-specified service entrance conductors

• Service clamp(s), locknut/bushing, anti-short bushings as required

• Anti-oxidant compound (for aluminum conductors)

• Grounding electrode conductor (GEC), clamps, and ground rods (typically two, min. 6 ft apart; verify depth and spacing locally)

• Cable connectors (snap-in or locknut type) for NM-B/Romex (3/8 in., 1/2 in., 3/4 in., etc.)

• Assorted breakers: standard, AFCI, GFCI, or dual-function per code

• Panel screws, wood screws, nail plates, cable staples/straps

• Duct seal (to weather-seal exterior penetrations)

• Circuit directory labels

3) Panel selection and placement

• Choose a service-rated 200-amp panel compatible with your utility and meter/disconnect arrangement. Plug-on neutral panels simplify neutral terminations for AFCI/GFCI.

• Standard stud bays (16 in. o.c.) provide ~14½ in. space; many 200-amp panels are ~14¼ in. wide to fit between studs.

• Pick a location that meets clearance, height, and accessibility rules and suits feeder routing and future expansion (e.g., space for a subpanel feeder).

4) Mounting the panel

1. Open the can: Remove the dead front and interior cover. Identify factory knockouts and mounting holes.

2. Set height: Mark a level line such that the highest breaker handle will be ≤ 6′7″ (typical rule).

3. Anchor: Use the four corner mounting points or side studs. Drive appropriate wood/structural screws with washers. Check plumb and level.

Tip: If mounting between studs in new construction, installing a backing board or blocking can make fastening easier and cleaner.

5) Bringing in the service entrance cable

The service side is utility-regulated. If your service disconnect is elsewhere (e.g., outside), your indoor panel is a subpanel and must be wired accordingly (neutral and ground isolated).

1. Pick the knockout sized for the service clamp (e.g., 2 in.).

2. Install the connector/clamp, tighten the locknut, and add a protective bushing.

3. Feed the SE/U into the panel.

4. Strip outer jacket carefully to avoid nicking insulation.

5. Form conductors to reach the lugs without strain.

6. If aluminum, apply anti-oxidant compound to the stripped portions.

7. Loosen main lugs, fully insert the ungrounded conductors (typically black and red) and the neutral conductor into their respective lugs, then torque to spec.

8. Install the lug covers per manufacturer requirements.

Do not land the equipment grounding conductor on the neutral bar in a subpanel. For a main service panel, bonding occurs here (see next section).

6) Bonding and grounding (ground rods & electrode conductor)

Grounding electrode system (GES)

• Many jurisdictions require two ground rods, spaced at least 6 ft apart (or demonstrate low enough resistance with one rod; check code).

• Use listed acorn clamps to connect the bare copper GEC (gauge per code; e.g., #6 Cu commonly used for 200 A in some jurisdictions, but many require #4 Cu—verify locally).

• Run the GEC unspliced from the panel to rod #1, continue to rod #2, then back to the panel, or use continuous run through both rods (no mid-span cuts).

Inside the panel

• Land the GEC on the grounding bar designated for equipment grounds/GE conductors.

• If this is the service disconnecting means (main service panel), install the bonding screw/strap to bond the neutral bar to the panel can as required.

• If this is a subpanel, do not bond the neutral; neutrals must be isolated from the can, and grounds must terminate on a separate ground bar bonded to the can.

Seal penetrations with duct seal to block moisture/air.

7) Preparing for homeruns (cable management & knockouts)

1. Plan entry points: Mark top/bottom knockouts you’ll use for NM-B homeruns.

2. Install Romex connectors (snap-in or locknut). Size them for the cable (e.g., 3/8 in. for 12/2, 1/2 in. for 10/2, 3/4 in. for 10/3, etc.).

3. Drill a cable chase above the panel (often a row of holes through the top plate or blocking).

4. Staple/support NM-B as required (commonly within 12 in. of the panel and at prescribed intervals). Add nail plates where cables pass near edges.

8) Terminating branch circuits

• Strip jacket carefully; avoid nicking conductor insulation. Remove paper fillers.

• Label each run as soon as it enters the panel (a simple trick: slide a snipped piece of the printed jacket back over the black conductor as a temporary tag).

• Dress conductors: Route grounds to the grounding bar, neutrals to the neutral bar (or plug-on neutral interface where applicable), and hot conductors toward their future breaker locations. Keep wiring tidy and to the panel edges for accessibility and airflow.

• Trim to length: Leave enough slack for neat bends and future maintenance; avoid excess that crowds the can.

9) Installing breakers: standard, double-pole, AFCI/GFCI

Follow the manufacturer’s instructions for your panel and breakers. Use the correct series (e.g., Square D Homeline vs. QO).

A) Standard 120-V single-pole breaker (e.g., 15 A, 20 A)

• Terminate ground on the ground bar.

• Terminate neutral on the neutral bar (or plug-on neutral pad, depending on breaker style).

• Terminate hot (black) in the breaker lug. Torque to spec.

• Clip the breaker to the bus and neutral rail as designed.

B) Double-pole 240-V breaker (e.g., 30 A water heater, 40–60 A HVAC, etc.)

• Use the correct cable and conductor sizes per the equipment nameplate and code.

• Typically two ungrounded conductors (e.g., black/red) land on the two lugs of the double-pole breaker.

• Neutral: only if the load requires it (many straight-240-V loads do not); if repurposing a white as an ungrounded conductor, re-identify it per code.

• Ground lands on the ground bar.

C) AFCI, GFCI, and dual-function breakers

• Modern dwelling circuits often require AFCI, GFCI, or dual-function protection by code (locations and combinations vary).

• Plug-on neutral breakers simplify wiring: the breaker’s neutral jaw contacts the neutral rail, and the branch neutral conductor terminates at the breaker’s neutral terminal (check your model; some brands still use a pigtail).

• Land hot on the breaker’s hot terminal, neutral on the breaker’s neutral terminal (if required by the breaker design), ground on the ground bar.

• Snap in per the panel’s instructions and test using the built-in TEST button after energizing.

Label everything in the circuit directory as you go. Keep the schedule synchronized with breaker positions.

10) Feeding a future subpanel (100-amp example)

A common upgrade is to reserve capacity for a detached garage or workshop.

• Choose a 2-pole feeder breaker sized for the subpanel (e.g., 100 A).

• Use conductors sized for the feeder ampacity and length (e.g., aluminum SER or XHHW in conduit, or copper THHN/THWN in conduit—size per code and voltage drop considerations).

• A typical 120/240-V feeder includes two hots (A/B), one neutral, and an equipment grounding conductor.

• In the main service panel:

  • Land the two hots on the 2-pole breaker.

  • Land the neutral on the neutral bar (torque-rated lug as needed).

  • Land the EGC on the ground bar.

• In the subpanel:

  • Isolate the neutral bar from the can (remove bonding screw/strap).

  • Bond the ground bar to the can.

  • If detached building: provide a grounding electrode system at that structure per code.

If transitioning to conduit for an exterior underground run, use an accessible junction box, proper connectors, and conduit rated for burial depth. Coordinate trenching, burial depth, and marking with local code and utility locates.

11) Dressing the panel, covers, and labeling

• Neaten conductors along the can edges; avoid bundling tightly across the center. Keep bend radii gentle.

• Install any remaining lug covers and barrier shields required by the panel manufacturer.

• Knock out dead-front tabs that correspond to installed breakers; insert filler plates for any missing spaces.

• Install the dead front and panel cover with the supplied screws; do not overtighten.

• Complete a clear, legible circuit directory: room + load details (e.g., “Kitchen small appliance #1,” “Bath GFCI,” “Dryer 30 A,” “HVAC air handler,” “Garage subpanel feeder 100 A”).

12) Pre-inspection checklist

Use this quick pass before calling for inspection:

•  Permit posted and work area accessible/clear

•  Working space clearances met (width, depth, height)

•  Panel height compliant; all unused openings filled

•  Conductors sized correctly; torque values met (keep torque chart/labels handy)

•  Service neutral bonded only where appropriate (main) and isolated in subpanels

•  Grounding electrode system installed: required number of rods, spacing, clamps, continuous GEC, correct gauge

•  Cable connectors used at all knockouts; jackets extend into panel as required

•  NM-B supported and stapled to code; nail plates installed where needed

•  Branch circuits on appropriate AFCI/GFCI/dual-function protection where required

•  Accurate circuit directory completed

•  Penetrations sealed (e.g., duct seal on exterior openings)

•  Dead front secured; no exposed live parts

13) Frequently asked questions

Do I bond the neutral bar to the can?

Only at the service disconnecting means (often the main service panel). Subpanels must have isolated neutrals and separate bonded ground bars.

Are two ground rods required?

Many jurisdictions require two rods at least 6 ft apart unless you can prove low resistance with a single rod. Follow your local rules.

What size grounding electrode conductor for 200 A?

This varies. Some inspectors accept #6 Cu for two rods; others require #4 Cu. Always size per the NEC table and local amendments.

Where do AFCI and GFCI apply?

Dwelling rules change over time. Kitchens, baths, laundry, outdoors, garages, and most living areas often require AFCI/GFCI/dual-function protection. Check the latest code cycle adopted in your area.

Can I re-identify a white conductor as hot?

Only where permitted and only in specific conditions (e.g., cable assemblies for certain 240-V loads). If allowed, permanently re-identify at all accessible points with tape or other means.

Do I need a torque screwdriver?

Yes. Breakers and lugs list required torque values. Improper torque can cause overheating or connection failure.

Final thoughts

A clean, code-compliant panel is the backbone of a reliable electrical system. Plan the layout, protect the service entrance, build a robust grounding/ bonding scheme, keep branch-circuit wiring organized, and choose the right protective breakers for each circuit. When in doubt, lean on a licensed electrician and your local authority having jurisdiction (AHJ). A meticulous install today prevents nuisance trips, hot connections, and safety hazards tomorrow.