This is a tricky situation, and good on you for going in with a power quality analyzer! Here's a breakdown of possible causes and what you should check with your readings

Possible Causes (Beyond the Obvious):
Voltage Drop Under Load

The 208V service could be sagging significantly under load, even if it's acceptable at no-load. A large voltage drop will cause the motors to draw more current to maintain the same power output (HP). This is the most likely culprit if the amprobe readings were only taken briefly.

Harmonics

Non-linear loads (like variable speed drives, if present) can introduce harmonic currents into the system. These harmonics don't show up on a simple amprobe reading but can cause significant heating and nuisance tripping of breakers.

High Neutral Current

In a 208V single-phase system, you can sometimes get high neutral current even with balanced loads. It's less common, but still worth checking.

Loose Connections

Loose connections anywhere in the circuit (panel, breakers, motor connections, etc.) can cause increased resistance, leading to heat buildup and premature breaker tripping.

Motor Overheating

The motors themselves could be overheating due to poor ventilation, a failing capacitor (if capacitor start/run motors), or bearing issues. While not directly related to the electrical feed initially, overheating will cause the motor to draw more current.

Ambient Temperature

If the panel is located in a hot environment, the breakers may be derated and tripping at a lower current than their rating.

Breaker Derating Over Time

Breakers can become more sensitive and prone to tripping over time, especially if they have experienced repeated overloads. However, since the contractor replaced the breakers multiple times, this is less likely, but still a remote possibility.

Backfeed from other sources

Check to see if there is a secondary supply backfeeding onto the grid during operation of the pool pumps.

What to Check with Your Power Quality Analyzer

Here's what you need to measure and analyze:1.

Voltage (L-N) and Current (L) - Real-Time Recording



Record for an extended period

Ideally, record voltage and current on each branch circuit feeding the pumps before they start, during startup, and for as long as they run until tripping occurs.

Look for Voltage Sag

Watch for a significant voltage drop when the pumps start and as they run. Note the actual voltage at the panel and at the motor terminals if possible.

Current Fluctuations

Check for any unusual current spikes or fluctuations beyond the nameplate rating.2.

Harmonics Analysis



THD (Total Harmonic Distortion) of Voltage and Current

High THD indicates significant harmonic content. A high THD of current is most concerning.

Individual Harmonic Components

Identify the dominant harmonic frequencies (e.g., 3rd, 5th, 7th).

Neutral Current

Measure and record neutral current. Compare it to the phase currents. Excessively high neutral current is a problem.3.

Power Factor



Measure power factor at the panel and at the motor terminals. A low power factor (significantly below 0.85) indicates reactive power, which increases current draw. This could point to an issue with the motors or the capacitors (if applicable).
4. Temperature (If Possible)

Use an infrared thermometer to check the temperature of the breakers, motor windings, and connections while the pumps are running. Overheating is a critical clue.

Troubleshooting Steps Based on Readings



Voltage Drop

If voltage is dropping significantly, you have an undersized service, undersized wiring, or excessive distance from the panel. Options: Upgrade the service. Run larger gauge wire to the pumps. Consider a voltage boost transformer.

Harmonics

If harmonics are high, you need to mitigate them. Options: Install harmonic filters. Use motors with lower harmonic distortion.

High Neutral Current

Check for unbalanced loads elsewhere in the panel or improper neutral connections.

Overheating

If breakers or motors are overheating, address the cause: Improve ventilation. Replace faulty motors or capacitors. Tighten all connections.

Important Safety Considerations



Lockout/Tagout

Always de-energize the circuit before working on electrical equipment.

Personal Protective Equipment (PPE)

Use appropriate PPE, including safety glasses, gloves, and insulated tools.*

Qualified Personnel

Ensure you are qualified to perform electrical measurements and troubleshooting. If not, consult with a licensed electrician.

Good luck! Take thorough readings, document everything, and you'll likely find the root cause. Flag for review