How to find the right Thermal-Magnetic Circuit Breakers AI guide
Written by an AI model from its trained knowledge.
What the AI looks for in Thermal-Magnetic Circuit Breakers
- Exact panel type
- Match the family on the panel label (for example QO, Homeline, BR, CH, QP, THQL) Thermal-magnetic breakers are the standard home breaker, and fit to the bus is the first rule.
- Wire-size limit
- Copper: 15 A on 14 AWG, 20 A on 12 AWG, 30 A on 10 AWG unless code allows otherwise for specific motor or appliance loads The thermal element must trip before the conductor overheats.
- Interrupting rating
- The AIC rating must meet or exceed the available fault current at the panel (10 kA common, 22 kA or higher on some services) The magnetic element must safely clear short circuits.
- HACR / SWD markings
- Use HACR-marked breakers for HVAC equipment that calls for them, and SWD-marked breakers when used as a lighting switch Equipment nameplates and code may require these specific markings.
- Code-required upgrades
- Check whether the circuit now requires AFCI or GFCI before buying a plain breaker Replacing an old breaker can trigger current protection requirements.
Brands that matter
- Square D (Schneider Electric): QO (premium, with visible trip indicator) and Homeline (economy); not interchangeable.
- Eaton: BR (1 inch) and CH (3/4 inch) families; Type CL classified replacements.
- Siemens: QP family for Siemens and many Murray panels.
- GE (ABB): THQL for GE load centers.
What to avoid
- A larger breaker installed to stop trips on existing wire
- Tandem breakers in slots or panels not rated for them
- Counterfeit breakers sold loose or with mismatched labeling
Questions
Why is it 'thermal-magnetic'?
A bimetal (thermal) element trips on sustained overload, and a magnetic coil trips instantly on short circuits. Almost every standard residential and light-commercial breaker works this way.