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:
- Power off main (entire panel)
- Remove panel cover
- Pull old breaker (one wire then snap from bus)
- Install new breaker
- Replace cover
- Power on main
- Test new breaker
- 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
References
- NEC (National Electrical Code)
- Manufacturer breaker specifications
- UL standards for circuit breakers
- Manuall internal: Common Breaker Issues, Reading Electrical Panel Condition