Electrical Education / Panel Guide
Haik Electric • Electrical Education
Electrical Panels & Compatible Breakers
What is an electrical panel?
An electrical panel, often called a breaker box in a home, distributes power to individual circuits. A branch breaker shuts off its circuit if it detects an overload or short circuit.
Some panels have a main breaker that shuts off power to the circuits they supply. Other panels are supplied through a breaker or disconnect located elsewhere.
External references open in a new tab.
Circuit Breaker Types and What They Do
The family name, such as QO or BR, identifies a product line. Within a family, check the exact protection type, pole count, mounting style, and ratings.
| Protection type | What it does |
|---|---|
| Standard thermal-magnetic | Trips on sustained overloads or high short-circuit current. |
| AFCI (Arc-Fault Circuit Interrupter) | Detects hazardous electrical arcing to help reduce fire risk. A combination-type AFCI detects both series and parallel arcing. |
| GFCI (Ground-Fault Circuit Interrupter) | A Class A GFCI breaker detects current leaking from the intended path and shuts off power to help protect people from electric shock. |
| Dual-function AFCI/GFCI | Provides both AFCI and Class A GFCI protection in one breaker. Look for both functions in the product markings. |
In homes, AFCI protection is common on circuits serving living areas. GFCI protection is common in bathrooms, garages, and outdoors. Some circuits need both. Check the applicable electrical code and local requirements for the specific circuit.
Poles, panel spaces, and mounting
- Single-pole breakers commonly serve 120-volt home circuits. Two-pole breakers commonly serve 240-volt or 120/240-volt loads. Three-pole breakers commonly serve three-phase equipment or feeders.
- Tandem breakers typically provide two independent single-pole circuits in one panel space. Verify the tandem type and permitted positions on the panel label.
- Plug-on and bolt-on describe how a breaker attaches to the panel bus. Plug-on neutral describes a separate connection and requires a compatible panel. Some models use a neutral pigtail.
- Molded-case circuit breakers (MCCBs) are common in commercial and industrial distribution. Options include thermal-magnetic and electronic trip units. Some electronic models offer adjustable settings.
Read the ratings. Check amperage, voltage, pole count, and interrupting rating. The interrupting rating, often shown as kA or kAIC, tells you how much fault current the breaker can interrupt at its rated voltage.
References · CPSC AFCI and GFCI guide · Schneider Electric dual-function and neutral options · Schneider Electric tandem guidance · Eaton molded-case trip options
Residential load centers
Home lighting, outlets, and dedicated appliance circuits.
| Brand | Panel series | Example breaker families |
|---|---|---|
| Square D | QO | Type QO |
| Square D | Homeline | Type HOM |
| Eaton | BR | Type BR |
| Eaton | CH | Type CH |
| Siemens | PN and SN | Type QP |
Older Panel Brands & Current Breaker Replacements
How to identify your older panel
Look for the factory label inside the panel door, with the protective cover in place. If the label is visible, take a clear photo to share with your electrician.
Sample factory label · Illustrative fields
- Manufacturer
- The company name or logo
- Panel catalog number
- The complete model number, including any suffix
- Permitted breaker types
- The breaker type codes printed on the label
Use the label information and the manufacturer’s replacement chart to verify the exact breaker. If the label is missing or unreadable, have an electrician identify the equipment.
Documented breaker replacement examples
| Older brand | Original breaker type | Current breaker family to verify |
|---|---|---|
| Cutler-Hammer | CH | Eaton CH |
| Bryant or Westinghouse | BR | Eaton BR |
| Challenger | C, HC, or VC | Eaton BR for C, BRH for HC, and BRHH for VC |
Verify the full breaker catalog number, including any suffix, along with mounting, pole count, amperage, voltage, interrupting rating, and any required AFCI or GFCI protection.
Manufacturer references · Eaton CH catalog · Eaton legacy breaker cross-reference
When to call an electrician
Visible scorching, a burning smell, or a breaker that trips repeatedly are reasons to have an electrician assess the panel and circuit. A replacement breaker alone leaves any existing damage to the bus or connections in place.
Commercial branch panelboards
Lighting, outlets, and equipment circuits in offices, stores, and similar buildings.
| Brand | Panel series | Example breaker families |
|---|---|---|
| Square D | NQ | QO plug-on and QOB bolt-on |
| Square D | NF | EDB, EGB, EJB |
| Eaton | Pow-R-Line Xpert PRL1X | BAB, QBHW |
| Eaton | Pow-R-Line Xpert PRL2X | GHB, GHQ |
| Siemens | P1 | BL or BQD, depending on configuration |
Manufacturer references · Square D NQ · Square D NF · Eaton · Siemens
Industrial power distribution panelboards
Feeders to machinery, larger equipment, and downstream panels. These series can also serve large commercial facilities.
| Brand | Panel series | Example breaker families |
|---|---|---|
| Square D | I-Line | PowerPacT I-Line mount, such as H, J, or L frame |
| Eaton | Pow-R-Line Xpert PRL4X | Power Defense molded-case breakers, frame varies by configuration |
| Siemens | P5 | 3VA molded-case breakers, including 3VA6 in the P5 plug-in configuration |
Electrical panel and subpanel upgrades · Illustrated 200-amp service guide