Stocking Circuit Breakers: What Fits Which Panel
Square D QO120CP ranks first for general service work, since its Visi-Trip window flags the open pole before you touch a handle. Siemens Q120 carries the same 10,000 AIC rating across Siemens, ITE and Murray buses. Eaton BR120 covers BR and Cutler-Hammer load centers still in service.
Square D QO120CP belongs in the first bin of any service truck, because QO load centers dominate residential panel work and the Visi-Trip flag shows a tripped pole at a glance. One restriction is absolute: it stabs onto QO buses only and will not seat in a Homeline panel. Crews working Siemens or Cutler-Hammer neighbourhoods need the Q120 and BR120 riding alongside it.
Brand loyalty matters far less here than what the existing panel label accepts. We compared published bus compatibility, AIC ratings, pole width, trip technology and the amperage range each line offers, then weighed what electrical contractors report about supply house availability and inspection outcomes. Every pick is a manufacturer-listed breaker for its own panel line, not a third-party classified substitute.
The best picks, ranked
Square D QO120CP
QO sits above Homeline in Square D’s residential range, and this 20 amp single pole is the line’s most-ordered part number. A red flag appears in the handle window the instant the breaker opens, so you find the faulted circuit without toggling every pole. Frame width is one inch, and the stab locks onto QO load centers only.
Pros
- Visi-Trip window identifies the open pole without toggling
- Trip curve holds tighter tolerance on motor-start circuits
- Stocked by nearly every electrical supply house
Cons
- Homeline panels reject it despite the shared brand
- No diagnostic LED, unlike the AFCI and GFCI picks here
Siemens Q120
QP breakers seat in Siemens, ITE and legacy Murray panels, covering a wide slice of housing built from the 1970s onward. Frame width is one inch and the interrupting rating matches the class at 10,000 AIC. Handle ties sold separately turn two singles into a 240 volt pair during a service call.
Pros
- One part number covers Siemens, ITE and Murray buses
- Handle tie accessory enables 240V conversions
- Multi-packs suit rough-in work on new construction
Cons
- Handle carries no trip indicator
- Corroded ITE bus stabs often need cleaning first
Eaton BR120
BR is Eaton’s high-volume residential line, and it replaces breakers in Cutler-Hammer and older Westinghouse load centers. Amperages run from 15A to 60A inside the same one inch frame, so a panel schedule rarely needs a second catalogue. Volume packs make this the easiest line to stock forty deep for a tract job.
Pros
- Volume packs match tract rough-in quantities
- Drops into Cutler-Hammer and Westinghouse panels still in service
- Covers 15A through 60A without changing footprint
Cons
- Eaton CH panels use a different bus and reject it
- No visual flag marks a tripped pole
Square D HOM120PCAFIC
NEC 210.12 pushes arc fault protection across bedrooms, kitchens and living areas, and this Homeline combination AFCI answers that in one inch of panel space. Plug-on neutral construction removes the pigtail, so wiring goes faster and the gutter stays clear for bending. Blink codes from the onboard LED separate an arc fault from a ground fault or a plain overload.
Pros
- Plug-on neutral removes one wire landing per device
- LED blink codes shorten callback diagnosis
- Satisfies combination AFCI rules for living areas
Cons
- Needs a Homeline panel with a plug-on neutral bar
- Shared neutrals on multiwire circuits cause nuisance trips
Siemens QF120A
Kitchen counters, baths, garages and outdoor receptacles all fall under ground fault rules. Protecting at the breaker covers every device on the branch instead of only the first outlet. QF120A trips at the Class A 5mA threshold and runs the periodic self-test that UL 943 now requires, with plug-on neutral mounting on current Siemens panels.
Pros
- Self-test cycle meets current UL 943 requirements
- Covers every outlet on the branch, not just the first
- Plug-on neutral saves a neutral landing per breaker
Cons
- Capacitive leakage on long runs can trip it
- Resetting means walking back to the panel
GE THQL1120
PowerMark Gold panels went into millions of homes from the 1970s onward, and THQL remains the listed replacement for them. ABB owns the line now, so current stock can arrive marked either way on GE-style packaging. Frame is one inch with a 10,000 AIC rating, and the same bus takes 15A through 50A.
Pros
- Correct listed part for GE PowerMark Gold panels
- Same bus accepts 15A through 50A
- Snaps in one-handed from a ladder
Cons
- Packaging alternates between GE and ABB branding
- No trip flag or diagnostic LED
Eaton BR230
Dryers, water heaters, well pumps and mini-split condensers all land on a two-pole 30 amp device. BR230 fills two adjacent one inch spaces and ties both handles internally, so a fault on either leg opens the pair. Bus compatibility matches BR120, which means one panel type covers your 120 and 240 volt work.
Pros
- Standard size for dryer and condenser circuits
- Internal tie opens both legs on a single fault
- Shares the BR bus with the single-pole pick
Cons
- Two spaces is a problem in an already full panel
- No ground fault protection where a spa or pump needs it
How they stack up
| # | Model | Amperage | Best for | Score | Price |
|---|---|---|---|---|---|
| 1 | Square D QO120CP | 20A, single pole | Best overall | 9.4 | Check price |
| 2 | Siemens Q120 | 20A, single pole | Best value | 9.2 | Check price |
| 3 | Eaton BR120 | 20A, single pole | Best budget | 9.0 | Check price |
| 4 | Square D HOM120PCAFIC | 20A, single pole | Best for AFCI code compliance | 8.8 | Check price |
| 5 | Siemens QF120A | 20A, single pole | Best for GFCI circuits | 8.6 | Check price |
| 6 | GE THQL1120 | 20A, single pole | Best for GE and ABB panels | 8.3 | Check price |
| 7 | Eaton BR230 | 30A, two pole | Best for 240V appliance circuits | 8.0 | Check price |
Before you buy
How to match a breaker to the panel Bus stab geometry differs between manufacturers, and that one detail decides the purchase. Square D alone sells two incompatible residential lines, QO and Homeline. Open the deadfront and read the label inside: it lists every accepted catalogue number. Third-party classified breakers do fit several buses mechanically. Manufacturers state that those parts void the panel listing, and enough inspectors reject them that most contractors skip the argument on permitted work.
AFCI vs GFCI vs dual function Arc fault devices watch for the electrical signature of damaged cable and loose terminations. NEC 210.12 places them on bedroom, kitchen and living area circuits. Ground fault devices watch for current leaking to earth, which is why counters, baths, garages, basements and outdoor receptacles call for them. Dual function parts fold both jobs into one space, useful when a panel has no room left. Where only one hazard applies, single-purpose breakers nuisance trip less on long branch runs.
When 10,000 AIC is not enough Interrupting rating describes the fault current a breaker can clear without coming apart. Residential branch breakers sit at 10,000 AIC almost universally, including every pick above. Service points close to a large utility transformer can see far more available fault current than that. Plan review then asks for 22,000 AIC devices or a documented series-rated combination. Ask the utility for the available fault current figure before ordering a panel schedule.
What to keep on a service truck Three single-pole 20 amp lines answer most emergency calls in mixed housing: QO, QP and BR. Add THQL where 1970s and 1980s GE neighbourhoods dominate the route. Two AFCI and two GFCI singles handle code upgrades that surface halfway through a job. One two-pole 30 amp covers dryer callbacks without a second trip. Go light on 15 amp singles, since 14 gauge wire cannot be moved up to a 20 amp breaker and the swap you actually get asked for runs the other direction.
Frequently asked questions
Can I put a different brand of breaker in my panel?
Only when the panel label names that breaker as acceptable. Classified breakers from third parties fit several buses mechanically, but manufacturers treat them as voiding the listing. Inspectors reject them often enough that matching the listed part is faster than defending the substitute.
What is the difference between Square D QO and Homeline?
QO is the premium line, with a tighter trip curve and the Visi-Trip window. Homeline is the value line sold heavily through retail. Their bus stabs are shaped differently, so neither breaker will seat in the other’s load center.
Which breaker do I need for a bedroom circuit?
Combination arc fault protection covers bedroom outlets under NEC 210.12. In a Homeline panel that means the HOM120PCAFIC or its equivalent; a QO panel takes the matching QO combination AFCI instead.
Is a plug-on neutral breaker worth it?
In a new panel, yes. Dropping one neutral pigtail per AFCI or GFCI device saves minutes each and frees gutter space for bending. Older panels without a plug-on neutral bar cannot use the feature at all.
How do I know if a breaker has tripped?
A tripped handle rests between on and off rather than fully off. Square D QO adds a red window that reads clearly in a dim basement. Reset by pushing the handle firmly to off, then back on.
Can a 20 amp breaker go on 14 gauge wire?
No. Fourteen gauge copper carries a 15 amp rating, so it must terminate on a 15 amp breaker. Oversizing removes the overcurrent protection the conductor depends on and fails inspection.
Why does my AFCI breaker keep tripping?
Shared neutrals between two circuits cause most of these calls. Universal motors in vacuums and older dimmers account for many of the rest. Modern combination AFCI breakers blink a diagnostic code that separates arc detection from a genuine overload.
Are two single-pole breakers the same as one two-pole breaker?
Not on a 240 volt load. A two-pole device such as BR230 opens both legs together. Two singles can leave one leg energised unless a listed handle tie joins them, which is why appliance circuits use the two-pole part.
How many breakers should a contractor keep in stock?
Depth matters more than variety. Ten to twelve 20 amp singles per common bus handles a week of service calls, plus a few AFCI and GFCI units and one two-pole 30 amp. Restock the line your route uses most rather than carrying every brand shallow.
Final word
Make the Square D QO120CP your default 20 amp single pole, because QO panels turn up constantly in service work and the Visi-Trip window saves minutes on every fault call. Keep Siemens Q120 and Eaton BR120 in the same drawer, since Murray and Cutler-Hammer panels will appear the same week. Pull the HOM120PCAFIC or Siemens QF120A only where code calls for arc fault or ground fault protection, as single-purpose breakers ride out long runs with fewer nuisance trips.
Jake Monroe
Jake worked as a residential contractor for over a decade before shifting to full-time writing. He evaluates power tools, hand tools and workshop gear through the lens of someone who has actually used them on job sites, not just read the box.
