Okay, you've got a classic nuisance tripping situation. Let's break down the problem and explore possible solutions, while being mindful of safety and code compliance.

Understanding the Problem



Inrush Current

Central vacuums, especially at startup, can draw a very high current spike (inrush current) that's significantly higher than their rated running amperage. This inrush is what's likely tripping the breaker, especially when the motor is cold (after a couple days of not being used).

GFCI Sensitivity

GFCI outlets are designed to detect even very small imbalances in current between the hot and neutral wires. The motor startup may have slight leakage that the GFCI perceives as a ground fault, causing it to trip. However, the fact that the standard breaker trips, even after removing the GFCI, indicates that the inrush current is the bigger culprit.

Breaker Degradation

Breakers can sometimes degrade over time, making them more sensitive to overloads than they should be.

Code Compliance

As you mentioned, NEC (National Electrical Code) requires GFCI protection for receptacles in garages.

Possible Solutions (In order of recommendation)


Try Replacing the Standard Breaker

The easiest and cheapest first step. Breakers can weaken over time. Replace the 20-amp breaker with a brand-new, identical 20-amp Square D breaker. See if this resolves the problem before trying anything else.

Reasoning

If the breaker has degraded and is tripping too easily, a new breaker with the proper tolerances could resolve your issue and be the easiest/most cost-effective first step.2.

High-Magnetic Breaker (Delayed Trip or HM Breaker)

As you mentioned, these breakers (like the Square D QO120HM) are designed to tolerate higher inrush currents without tripping. They have a higher magnetic trip threshold, specifically for dealing with motor loads.

How it works

The "HM" designation means it has a "high magnetic" trip curve. Standard breakers trip almost instantly when there's a significant overload (short circuit) or when the current exceeds the rated amperage for a sustained period. HM breakers are designed to allow a brief, high inrush current (like a motor starting) without immediately tripping.

This is the most likely solution to work. Recommendation

If replacing the standard breaker does not solve the issue, This is your next best step.

Important

Make sure the HM breaker you choose is compatible with your panel and is the correct amperage (20A in your case). Also, note that many people do not like these in the house, and prefer regular breakers due to the faster tripping. Keep this in mind.

GFCI with HM Breaker

If installing an HM breaker in place of the Standard Breaker in the Panel Still has an Inrush that interferes with the GFCI downstream (in the Garage), removing the GFCI in the Garage is only a last resort.

Consider using a GFCI breaker rather than an outlet. This will protect the circuit and is also generally an approved solution.3. Dedicated Non-GFCI Circuit (If HM Breaker Doesn't Fully Solve GFCI Issues AND Code Allows a Variance)



This is your last resort, and requires careful consideration of code and safety. First, consult with a licensed electrician. Explain the situation and ask if there's any way to get a variance on the GFCI requirement specifically for this dedicated circuit. They may know local interpretations of the code or have alternative solutions. If a variance is possible, remove the GFCI outlet and replace it with a standard outlet. Make absolutely sure the circuit is still properly grounded. Reasoning

This completely eliminates the GFCI's sensitivity to any potential motor leakage. However, it removes GFCI protection in the garage, which is generally against code.4.

Time-Delay Fuse (Potentially Dangerous, Not Recommended for Beginners)

While some recommend slow-blow fuses, fuses are not typically used in residential panels anymore. Breakers are much safer and more convenient. I would strongly advise against this approach unless you're very experienced with electrical work.

Important Considerations



Consult a Licensed Electrician

Electrical work can be dangerous. If you're not comfortable working with electrical panels and wiring, hire a qualified, licensed electrician. They can diagnose the problem accurately and ensure the work is done safely and to code. They can also advise you on the best solution for your specific situation and local codes.

Safety First

Always turn off the power to the circuit at the main breaker before working on any electrical components.

Amperage Ratings

Never replace a breaker or fuse with one of a higher amperage rating than what's specified for the circuit. This can create a fire hazard.

Documentation

Keep records of any changes you make to the electrical system.

Troubleshooting Steps

Before spending money on parts, try these diagnostic steps:1.

Double-Check Connections

Make sure all wire connections (at the breaker, the receptacle, and the vacuum unit) are tight and secure. Loose connections can cause voltage drops and potentially contribute to tripping.2.

Test Other Garage Outlets

Plug other devices that draw a similar amount of current (e.g., a shop vacuum, a power tool) into the same GFCI outlet. Does the GFCI trip with those devices? This helps isolate whether the problem is specific to the central vacuum or a general issue with the outlet or circuit.3.

Observe and Record

Keep a log of when the tripping occurs (time of day, how long the vacuum has been unused, etc.). This information might help identify a pattern.

Summary of Recommendations


Start with the simplest and cheapest

Replace the standard breaker with a new one of the same type.2.

If that doesn't work

Replace the breaker with a High-Magnetic Breaker (HM).3.

If the HM Breaker Does not help or interferes with GFCI Outlet

Contact a licensed electrician to discuss potential code variances and whether a dedicated non-GFCI circuit is possible.4.

Avoid using time-delay fuses unless you're very experienced and comfortable with electrical work.By systematically addressing the possible causes, you should be able to resolve the nuisance tripping and get your central vacuum working reliably and safely. Flag for review