Okay, let's break down your questions about upgrading your sub-panel with Leviton breakers and your concerns about AFCI/GFCI, hydraulic vs. thermal breakers.

AFCI/GFCI Breakers on All Circuits Upsides



Increased Safety

This is the primary benefit. AFCI breakers detect arc faults (dangerous electrical sparks) that standard breakers won't catch, preventing fires. GFCI breakers detect current leakage to ground, preventing electrocution, especially in damp locations or near water. Covering all circuits offers the maximum protection.

Code Compliance (Future-Proofing)

Building codes are becoming stricter, requiring AFCI/GFCI protection in more areas. Outfitting all circuits now avoids potential future upgrades.

Potential Downsides/Considerations



Cost

AFCI/GFCI breakers are significantly more expensive than standard breakers.

Nuisance Tripping

This is the biggest concern. AFCI/GFCI breakers are sensitive and can trip due to electrical noise, certain appliance designs (especially older or poorly designed appliances with universal motors), or wiring issues that aren't a safety hazard but still create minor leakage or arc-like behavior.

Complexity

Troubleshooting nuisance trips can be challenging and time-consuming. You'll need to systematically isolate the problem circuit and appliance.

Compatibility

While less common now, some older appliances or devices might be incompatible with AFCI/GFCI breakers and cause persistent tripping.

GFCI Breakers on 2-Pole 40A/50A Circuits (EV Charger, Range, HVAC) Code Requirements

Local and national electrical codes may require GFCI protection for specific appliances and situations. Check your local requirements. EV chargers, for example, are often required to have GFCI protection. Ranges and HVAC may not be.

EV Charger

GFCI protection is very common and recommended for EV chargers. The location (garage, outdoors) and charging level often necessitate it.

Range and HVAC

This is less common, but not necessarily a bad idea. While you might experience more nuisance tripping, it would increase safety.

Specialized GFCI

For EV chargers and certain other dedicated circuits, you might want to consider "EVSE GFCI" breakers. These are designed to be more tolerant of the charging process's inherent noise and potential leakage, reducing nuisance trips. The same applies to the "Motor Protector" GFCI breakers that can handle some of the noise generated by electric motors in HVAC.

Hydraulic vs. Thermal Breakers Operating Principle



Thermal Breakers

Use a bimetallic strip that bends when heated by overcurrent, tripping the breaker. They are dependent on the ambient temperature.

Hydraulic-Magnetic Breakers

Use a solenoid coil and a hydraulic time-delay mechanism. Overcurrent energizes the coil, pulling a plunger through a fluid-filled tube to trip the breaker. More consistent behavior across temperature variations.

Advantages of Hydraulic-Magnetic



Temperature Stability

More accurate tripping characteristics across a wider temperature range. Not significantly relevant for most residential applications.

Trip Curve Consistency

More consistent and predictable tripping behavior over time.

Arc Quenching

Often have better arc-quenching capabilities.

Trip Speed

This is where it gets complicated.

Instantaneous Trip

For very high overcurrents (short circuits), both types should trip very quickly (within milliseconds).

Time-Delay Trip

For moderate overcurrents (overloads), both types have a designed time delay to allow for temporary surges (e.g., motor starting). The specific trip curve (time vs. current) is what matters most, and that depends on the breaker's design and manufacturer. Generally, hydraulic-magnetic breakers are known for slightly more precise and predictable time-delay tripping, but the difference is usually negligible in residential applications.

Disadvantages of Hydraulic-Magnetic



Cost

More expensive.

Availability

Less common, especially in standard residential panels.

Which Breaker Trips Quicker, Thermal or Hydraulic?

As mentioned above, this depends on the level of the overcurrent. For a direct short, they should both trip very quickly. If we are talking about overload, the trip time will be affected by the specific breaker's trip curve.

Overall Recommendation1. AFCI/GFCI

If cost isn't a major concern, using AFCI/GFCI breakers on all 15A and 20A circuits is a very good safety measure. Be prepared for potential nuisance tripping and the need to troubleshoot.2.

Range/HVAC

This is dependent on code. Check the local requirements.3.

EV Charger

If you're installing an EV charger, GFCI protection is highly recommended (and likely required by code). Look for "EVSE GFCI" breakers to minimize nuisance tripping.4.

Hydraulic vs. Thermal

In most residential applications, the benefits of hydraulic-magnetic breakers don't justify the added cost and reduced availability. Standard thermal breakers are generally adequate.

Important Considerations



Consult a Qualified Electrician

Always consult with a licensed electrician for any electrical work, especially panel upgrades. They can assess your specific needs, ensure code compliance, and handle the installation safely. They will also be familiar with local codes that may influence your AFCI/GFCI requirements.

Leviton's Future

Be aware that Leviton is a relatively new player in the breaker market compared to established brands like Square D, Eaton, and Siemens. While their products might be good, the long-term availability of replacement breakers is something to consider.

Troubleshooting

If you experience nuisance tripping, don't immediately assume the breaker is faulty. Systematically check the wiring and appliances on the affected circuit. Consider using a circuit analyzer tool to look for ground faults or arc faults.

Proper Installation

The most important factor for breaker performance and safety is proper installation. Ensure all connections are tight and wiring is correct.

Warranty Information: Review the warranty information for both thermal and hydraulic breakers and note that it only covers the cost of the breakers, not the labor to replace them.By carefully considering these factors and consulting with a qualified electrician, you can make informed decisions about upgrading your sub-panel for safety and reliability. Good luck! Flag for review