Common Circuit Breaker Types Reference

Why this matters

Circuit breakers vary widely - different types, brands, technologies. The tech who knows breaker types makes correct replacements + understands what's installed. This is the field card.

Breaker function categories

Standard breakers:

• Overcurrent protection
• Short circuit protection
• Basic function
• Most common

GFCI (Ground Fault Circuit Interrupter):

• Detects current to ground
• Trips quickly (milliseconds)
• Safety for shock prevention
• Required wet locations

AFCI (Arc Fault Circuit Interrupter):

• Detects arcing in wiring
• Prevents fire from arc
• Required many areas
• Newer technology

DF / Dual-Function:

• AFCI + GFCI combined
• Newer requirement
• Single breaker, both protections

HID breaker:

• For high-amperage motor loads
• Slow-blow characteristic
• Specialty

SWD breaker:

• For switching duty (lights)
• Cycling tolerance

Brand identification

Major brands:

Square D (Schneider Electric):

• Homeline: residential
• QO: residential + commercial
• Most common new construction
• Pink "HOM" OR QO marking

Eaton (Cutler-Hammer):

• BR: residential
• CH: residential + commercial
• Common
• Black housing typical

Siemens:

• Q-series
• Black housing
• Common

GE:

• THQL series
• Residential common (production ceased 2018)
• Spare parts available

Federal Pacific (FPE) [Caution]:

• Stab-Lok
• Pre-1980s
• Documented failures
• Recommend replacement

Zinsco [Caution]:

• Pre-1970s typically
• Documented failures
• Recommend replacement

Standard breaker specs

Voltage rating:

• 120V (single-pole, 15-20A)
• 240V (double-pole, 20-50A)
• Higher for commercial

Amperage rating:

• 15A (lighting / general)
• 20A (kitchen, bathroom)
• 30A (water heater, dryer)
• 40-50A (range, HVAC)
• 100-200A (main, sub-panel feeder)

Slot count:

• Single-pole (one slot)
• Double-pole (two slots, 240V)
• Three-pole (three-phase commercial)

GFCI breakers

Function:

• Senses ground fault
• Trips at 5mA difference
• Saves life from shock

Common locations required:

• Bathrooms
• Kitchens (above counter)
• Outdoors
• Garages
• Unfinished basements
• Wet locations

Types:

• Breaker (whole circuit)
• Outlet (just that outlet)
• Both available

Per NEC:

• Detail per current code
• Updates over time

AFCI breakers

Function:

• Detects arcing
• Prevents fire from damaged wiring
• Newer technology

Required locations (per current NEC):

• Bedrooms
• Living rooms
• Dining rooms
• Many living areas
• Continues expanding per NEC updates

Common false trips:

• Some motor loads (vacuums)
• Some appliances
• Newer AFCI less sensitive

Dual-Function breakers

AFCI + GFCI combined:

• Newer requirement many areas
• Single breaker
• Both protections

Replacement of GFCI OR AFCI:

• Sometimes with DF
• Cost slightly higher
• Comprehensive protection

Breaker amperage matching

Critical:

• Match wire size
• Per NEC

Standard:

• 14 AWG: 15A breaker
• 12 AWG: 20A breaker
• 10 AWG: 30A breaker
• 8 AWG: 40A breaker
• 6 AWG: 50-60A breaker

Never oversize breaker for wire:

• Fire hazard
• Wire can overheat before breaker trips

Breaker brand interchangeability

Generally NOT interchangeable:

• Different brands' breakers different sizes / contact configurations
• Sometimes physically similar; not safe

Use only listed compatible:

• Manufacturer's panel = manufacturer's breakers
• Some "classified" breakers UL-listed for other panels (limited)

Always:

• Match brand to panel
• Use OEM OR approved

Panel + breaker matching

Common panels + their breakers:

• Square D Homeline panel: Homeline breakers
• Square D QO panel: QO breakers
• Eaton BR panel: BR breakers
• Eaton CH panel: CH breakers
• Siemens Q panel: Q breakers
• GE THQL panel: THQL breakers

Different breaker = sometimes won't snap in properly OR safely.

Tandem / twin breakers

For tight panel space:

• Two breakers in one slot
• Per panel rating (some accept, some don't)
• Sometimes "CTL" (limit) restrictions
• Per code

Some panels prohibit:

• Per manufacturer
• Per code

Main breaker

At panel top:

• 100-200A typical residential
• Disconnects all
• Sometimes separate handle

Service disconnect:

• Outside (some areas)
• Main breaker (other)
• Per local code

Sub-panel breakers

Feed sub-panel:

• Larger breaker (main panel)
• Smaller breakers in sub-panel

Sub-panel from main:

• 60-100A typical
• Per load

Common failure modes

Tripping repeatedly:

• Real overload OR fault
• OR breaker bad

Won't reset:

• Sometimes stuck mechanically
• Sometimes circuit still has fault
• Sometimes breaker dead

Hot to touch:

• Loose connection
• Excessive load
• Investigate

Won't trip when should:

• Internal failure
• DANGEROUS
• Replace immediately

Customer's symptoms

"Breaker trips constantly":

• Identify cause
• Real fault OR nuisance
• Fix root cause

"Breaker won't reset":

• Try reset
• If fails: replace OR investigate
• Sometimes still has fault

"Breaker hot":

• Concern
• Loose connection likely
• Service immediately

When to replace breaker

Replace when:

• Failed (won't trip OR reset)
• Hot consistently
• Damaged visible
• Outdated (rare)

Don't replace to "solve" tripping:

• Cause the tripping (real fault)
• New breaker also trips
• Customer's frustration

When trip is real

Investigate:

• What's on circuit?
• What was happening?
• Overload OR short?

Address:

• Reduce load
• Repair fault
• Replace failing equipment

When trip is nuisance

Sometimes:

• Sensitive AFCI
• Motor inrush
• Some equipment incompatible

Sometimes:

• Newer AFCI helps
• Sometimes accept
• Sometimes circuit redesign

GFCI test button

Should test monthly:

• Press test button
• Should trip
• Reset

Customer education:

• Most don't test
• Sometimes failed GFCI
• Annual recommendation

AFCI test button

Similar:

• Should test periodically
• Verify operation

When breaker installation

Process:

1. Power off main (entire panel)
2. Remove panel cover
3. Pull old breaker (one wire then snap from bus)
4. Install new breaker
5. Replace cover
6. Power on main
7. Test new breaker
8. Verify circuit operation

Common installation mistakes

• Wrong brand
• Wrong amperage
• Loose connection (heat)
• Wire under wrong terminal
• Skipping cover replacement
• Not testing

When customer's panel old

Sometimes:

• Breakers no longer available
• Sometimes only specialty
• Sometimes panel replacement
• Customer's decision

When customer's FPE / Zinsco

Recommend replacement of panel:

• Documented failure issues
• Customer's safety
• Insurance sometimes requires

Difficult to replace breakers only:

• Often FPE / Zinsco breakers harder to find
• Sometimes specialty suppliers
• Customer's investment in safety

Specific common scenarios

Customer wants a circuit added and the panel is full:

• Check the panel label for the maximum number of poles and which positions accept tandems (CTL positions). Not every slot does.
• A tandem in a non-CTL position is a listing violation, and a rejection-clip panel will not take one anyway.
• If tandems are not allowed, the options are a sub-panel or a service upgrade. Price both.

Bedroom, living area, or hallway circuit gets extended:

• Arc-fault protection follows the current code adoption in that jurisdiction. Extending an existing circuit commonly triggers it.
• If the panel brand has no AFCI breaker available, an outlet-branch-circuit AFCI device at the first outlet is the workaround.

Kitchen or bath remodel:

• Small-appliance and bath branch circuits need ground-fault protection, and in many adoptions arc-fault as well, which is where the dual-function breaker earns its place.
• Verify which the local inspector expects before you order the parts.

Refrigerator or freezer on a GFCI that keeps tripping:

• Confirm it is a real ground fault first with an insulation check, not just the customer's word.
• Motor-driven appliances with worn insulation or a wet compressor terminal do leak. The fix is the appliance, not a smaller-protection breaker.

Outdoor equipment, hot tub, pool equipment:

• Ground-fault protection is required, and the disconnect location and working clearance matter as much as the breaker.
• Pool and spa work has its own rules on bonding. If you do not do that work regularly, refer it.

Air conditioner or heat pump circuit:

• Use the breaker type and maximum size printed on the equipment nameplate. That number is a maximum overcurrent device rating, not a wire-size formula.
• Motor loads need a breaker rated for that duty. A general-purpose breaker that nuisance-trips on compressor inrush is the wrong device, not a weak one.

Adding a sub-panel:

• Feeder gets four wires, and the neutral is isolated from the ground bus in the sub-panel. The bonding screw comes out.
• Size the equipment grounding conductor to the feeder overcurrent device.

Generator or transfer arrangement:

• A backfed breaker used as a supply requires a listed hold-down kit and a mechanical interlock so utility and generator can never be closed together.
• No interlock, no energizing. This is the scenario that kills linemen.

References

• NEC (National Electrical Code)
• Manufacturer breaker specifications
• UL standards for circuit breakers
• Manuall internal: Common Breaker Issues, Reading Electrical Panel Condition