Okay, this is a tricky one, but there are a few likely culprits why a standard Siemens AFCI is tripping while a Siemens AFCI/GFCI combo breaker isn't with the same loads. Here's a breakdown of possibilities, considering you've already tried multiple breakers

Understanding the Difference: AFCI vs. AFCI/GFCI
AFCI (Arc Fault Circuit Interrupter)

Designed to detect dangerous arcing conditions in a circuit. It looks for specific patterns of current and voltage that indicate an arc, which could be caused by damaged wiring, loose connections, or faulty appliances.

AFCI/GFCI (Arc Fault Circuit Interrupter/Ground Fault Circuit Interrupter)

Combines the arc fault detection of an AFCI with the ground fault detection of a GFCI. GFCI's look for current leakage to ground (e.g., through a person touching a live wire).

Possible Causes for AFCI Tripping (But Not AFCI/GFCI)


Neutral-Ground Bonding Issues (on the circuit or device under test)

This is probably the #1 suspect! If the neutral wire is bonded to ground at more than one point in the circuit (e.g., in the subpanel and in an outlet box, or inside a device under test), it can create circulating neutral currents. These circulating currents can mimic arc fault signatures, causing the AFCI to trip.

Testing



Verify Neutral-Ground Bond at Main Panel ONLY

Make sure the neutral and ground are only bonded together at the main service panel.

Check for bootleg grounds

Open up outlets and switches on the affected circuits. Look for situations where someone has connected the ground wire to the neutral wire to "cheat" and get a ground connection where one wasn't originally present.

Test devices for N-G bonding

Unplug the heat gun and vacuum and test between neutral and ground with a multimeter. There should be no continuity, or at least a very high resistance, unless they have some specific internal filter.

Use an outlet tester

While not definitive, a 3-light outlet tester can sometimes indicate wiring problems, including bootleg grounds.2.

Marginal AFCI Breaker

Even though you've tried multiple breakers, it's still possible you got another slightly over-sensitive AFCI. It happens.

Testing

This is difficult without specialized AFCI testing equipment. Trying yet another breaker from a different source is the only real option here. If you have another circuit that definitely works with an AFCI, temporarily swap it to the problem circuit to see if it trips.3.

Loose Connections

Loose connections create resistance and can generate arcs. While you've likely checked, double and triple-check all connections on the affected circuits: At the breaker. At every outlet, switch, and junction box. Even at the light fixtures. Pay close attention to neutral connections! A loose neutral is a common cause of AFCI issues.4.

Problematic Appliances (Heat Gun or Vacuum)

Even if the AFCI/GFCI doesn't trip, it's possible one of these appliances is generating a small amount of arcing internally. The AFCI/GFCI might be slightly less sensitive, or the arcing might not be severe enough to trigger the GFCI portion.

Testing

Try the appliances on a different, known-good circuit protected by a standard AFCI breaker (if you have one). If it trips there too, you've likely found the culprit.

Try other appliances

Plug a few other known good appliances into the suspect circuit. If none of them trip the AFCI, the heat gun or vacuum is probably the problem.5.

Circuit Overload (Contributing Factor)

While you say the load isn't tripping the AFCI/GFCI, consider if the circuit is close to its maximum current capacity. A slightly high load, combined with another issue (like a loose connection), could be enough to push the AFCI over the edge.

Testing

Use a clamp meter to measure the actual current being drawn by the heat gun/vacuum on the circuit. Compare this to the breaker's rating (e.g., 15A or 20A).6.

Voltage Fluctuations

Significant voltage fluctuations (sags or surges) can sometimes trigger AFCIs. This is more common in areas with unreliable power grids.

Testing

Use a voltage data logger to monitor the voltage on the circuit over time. Look for unusual fluctuations.7.

Cross-Talk/Noise on the Line

Less common, but sometimes "noise" on the power line (from other appliances, electronic devices, or even external sources) can interfere with the AFCI's detection circuitry.

Testing

This is very difficult to diagnose without specialized equipment. Try turning off other large appliances in the area to see if it makes a difference.8.

Improper Installation (Less Likely, But Possible)

Ensure the AFCI breaker is properly seated in the panel and making good contact with the bus bars.

Why the AFCI/GFCI Might Not Trip When the AFCI Does



Lower Sensitivity

The AFCI portion of an AFCI/GFCI might have slightly lower sensitivity than a standalone AFCI. This is because the manufacturers have to balance the sensitivity of both the AFCI and GFCI components.

Different Detection Algorithms

The AFCI portion of the combo unit might use slightly different arc detection algorithms than the standalone unit.

Suppressed Noise

The AFCI/GFCI combo might have better filtering to suppress electrical noise that could falsely trigger the AFCI.

GFCI portion masking an arc

Sometimes the GFCI component of the breaker will trip first which will not allow the AFCI component to trip. This is especially true if the arc is also causing a ground fault.

Troubleshooting Steps


Start with the Obvious

Double-check all connections, look for visible damage to wiring, and try the appliances on a different AFCI-protected circuit.2.

Neutral-Ground Investigation

This is the most likely area to focus on. Carefully inspect for bootleg grounds and ensure proper N-G bonding at the main panel only.3.

Isolate the Circuit

Turn off all other breakers except the one for the circuit in question. Does it still trip? This helps rule out interference from other circuits.4.

Eliminate Appliances

Unplug everything from the circuit and turn on the breaker. If it holds, plug things back in one at a time until it trips. This helps identify the problem appliance.5.

Professional Help

If you've exhausted these steps and are still stumped, call a qualified electrician. They have the tools and expertise to diagnose more complex electrical problems.

Safety First! Always turn off the breaker before working on any electrical wiring.* If you're not comfortable working with electricity, hire a qualified electrician.Good luck! Let me know what you find. Flag for review