Yes, it is possible for an arc-fault circuit interrupter (AFCI) to have a "sweet spot" in which it trips under load but not without load. This can occur due to several factors

1. Loose Connections:

Under load, loose connections can generate intermittent arcing, which can trigger the AFCI. However, without load, the arcing may not occur or may be below the AFCI's detection threshold.2. Marginal Wiring

Marginal wiring, such as undersized conductors or poor insulation, can experience increased resistance under load. This can lead to localized heating, which in turn can create arcs that trip the AFCI.

3. Faulty Loads

Certain types of loads, such as inductive loads (e.g., motors) or loads with high inrush currents, can generate transient arcs during startup or operation. These arcs may be detected by the AFCI even though there is no sustained fault condition.

4. Sensitivity Setting

AFCIs have adjustable sensitivity settings. In some cases, the AFCI may be set to a higher sensitivity level, which makes it more prone to tripping under load conditions.

Addressing the Sweet Spot

To address the sweet spot, several steps can be taken:

Check Connections

Ensure that all connections are tight and secure.

Inspect Wiring

Inspect the wiring for any damage, loose connections, or undersized conductors. Repair or replace any defective components.

Identify Faulty Loads

Test the loads to identify any that may be causing the tripping. Replace or repair faulty loads.

Adjust Sensitivity: If necessary, adjust the sensitivity setting of the AFCI to a more appropriate level. Note that a lower sensitivity setting may increase the risk of false tripping.It is important to approach this issue with caution and ensure that the solution does not compromise the safety of the circuit. If the problem persists, it is recommended to consult a qualified electrician for further investigation and repair. Flag for review