Understanding Your Electrical Service Panel
Your electrical service panel is the distribution center for all the electricity in your home. Understanding how it works helps you troubleshoot problems, plan upgrades, and communicate with electricians.
What the Service Panel Does
Primary functions:
- Receives power from the utility via service entrance
- Distributes power to individual circuits throughout your home
- Protects circuits from overloads and faults
- Provides control for shutting off power to specific areas
- Contains safety devices that prevent fires and shocks
Anatomy of a Service Panel
Main Breaker
The large breaker at the top (usually):
- Controls all power entering the panel
- Rated for your service size (100A, 150A, 200A, etc.)
- Used to shut off all power in emergencies
- Protects the service entrance cables
Bus Bars
Metal bars inside the panel:
- Hot bus bars: Distribute power to circuit breakers
- Neutral bus: Connects all neutral wires
- Ground bus: Connects all ground wires
Important: In the main panel, neutral and ground connect together. In subpanels, they must be separate.
Circuit Breakers
Individual switches protecting each circuit:
| Breaker Type | Common Amperages | Typical Use |
|---|---|---|
| Single-pole | 15A, 20A | Outlets, lighting |
| Double-pole | 30A, 40A, 50A | Large appliances, HVAC |
| GFCI breaker | 15A, 20A | Wet locations |
| AFCI breaker | 15A, 20A | Bedrooms, living areas |
| Dual-function | 15A, 20A | Both AFCI and GFCI protection |
Types of Service Panels
Main Breaker Panel
Characteristics: - Contains main disconnect breaker - First point of power distribution - Neutral and ground bonded together - Grounding electrode connection
Subpanel
Characteristics: - No main breaker (or breaker sized for its feeder) - Fed from main panel via feeder cable - Neutral and ground separate (not bonded) - Adds circuits without upgrading main panel
Common uses: - Workshops or garages - Additions or renovations - Areas far from main panel
Panel Ratings and Capacity
What Your Rating Means
200-amp panel: - Maximum of 200 amps flowing through main breaker - Total of all circuits can exceed 200A (diversity factor) - Standard for modern homes
Breaker spaces vs. circuits: - Panel may have 30, 40, or more spaces - Single-pole breaker = 1 space - Double-pole breaker = 2 spaces - Tandem breakers = 2 circuits in 1 space (where allowed)
Capacity Considerations
Your panel may need upgrading if: - All breaker spaces are used - You're adding high-demand equipment - Breakers trip under normal use - You're planning major renovations
Reading Your Panel
The Panel Schedule
What it should show: - Each breaker position numbered - Circuit description ("Kitchen outlets," "Master bedroom") - Breaker amperage - Wire size used
If your panel isn't labeled: Have an electrician map it out. This is invaluable during emergencies.
Understanding Breaker Positions
- Odd numbers typically on left
- Even numbers typically on right
- Each vertical position alternates phases (A, B)
- 240V breakers span both phases
Common Panel Issues
Tripping Breakers
Occasional trips: Normal—the breaker is doing its job.
Frequent trips on one circuit: - Circuit is overloaded - Something on circuit has a fault - Breaker itself is failing
Multiple breakers tripping: - Major problem may exist - Could indicate main breaker or panel issues
Breakers That Won't Reset
Possible causes: - Active fault still on circuit - Breaker has failed - Wiring problem at panel
What to do: If reset doesn't hold, call an electrician.
Signs of Panel Problems
Visible signs: - Rust or corrosion - Burn marks or discoloration - Melted plastic - Loose or missing covers
Operational signs: - Buzzing sounds - Burning smell - Warm or hot panel cover - Flickering lights
Panel Safety
Safe practices:
- Know where your main breaker is
- Keep panel accessible (no storage in front)
- Replace missing knockouts
- Don't touch anything inside with power on
- Call a professional for any work inside the panel
Emergency procedure:
- Locate main breaker
- Flip to OFF position
- This shuts off all power except incoming service wires
- Call electrician for any suspected problems
When to Call an Electrician
Immediately: - Burning smell from panel - Sparks visible in panel - Panel feels warm or hot - Signs of water intrusion
Soon: - Breakers trip frequently - Breakers won't reset - You need additional circuits - Panel is outdated or damaged
For evaluation: - Home is 30+ years old - Planning renovations - Adding major appliances - Before buying/selling home
Panel Upgrades
Reasons to upgrade: - Increase capacity (100A to 200A) - Replace obsolete equipment (FPE, Zinsco) - Add spaces for new circuits - Improve safety with modern breakers
The process: 1. Evaluation and recommendation 2. Permit application 3. Utility coordination for disconnect 4. Panel replacement and circuit reconnection 5. Inspection and utility reconnect
Contact us for a panel evaluation or to discuss your electrical needs.