Okay, let's break down this motor circuit situation, focusing on code compliance and safe practices. You're right to be concerned, and your instincts are good. Bypassing the VFD introduces significant risks.

Key Considerations and Code References (2023 NEC unless otherwise specified)


Motor Full-Load Current (FLC) vs. Nameplate Amps

This is critical. You are correct. For branch circuit conductor sizing, you

must use the values in Table 430.250 of the NEC (Three-Phase AC Motors). The nameplate FLA is only used for overload protection. For a 5 HP, 208V, 3-phase motor, Table 430.250 lists 16.7 amps. The motor's nameplate FLA of 14 amps is for overload protection and sometimes for applying short circuit and ground fault protection. The "010A" might be a model number or an internal designation for the motor, rather than a specific current rating required to calculate amperage.2. Branch Circuit Conductor Sizing (NEC 430.22)

Minimum conductor ampacity: 125% of the Table 430.250 FLC. 16.7 amps 1.25 = 20.875 amps. You are correct. Given the code, you need conductors rated for at least 20.875 amps.

#14 AWG is almost certainly not sufficient. #14 AWG is typically only rated for 15 amps (see Table 310.16). Using #14 would be a code violation and a fire hazard. You'll need to consult Table 310.16 to determine the correct conductor size, considering insulation type and ambient temperature. Generally, #12 AWG copper is a good starting point for 20A circuits. Double-check the ampacity of #12 AWG with the insulation type (THHN, THWN, etc.) and installation conditions.3. Overload Protection (NEC 430.32)

This is where the nameplate FLA is important. Overload protection is designed to protect the motor from running at currents higher than its nameplate rating for extended periods.

Without the VFD

Overload protection is now the 20 amp breaker. This means it will trip slower than a fuse of 14 Amps or slightly above. Maximum Overload Protection Size: For motors with a service factor of 1.15 or more, or a temperature rise of 40°C or less, the overload protection can be set at a maximum of 125% of the nameplate FLA (NEC 430.32(A)(1)). For all other motors, the overload protection can be set at a maximum of 115% of the nameplate FLA (NEC 430.32(A)(1)). Based on your description, this likely applies to your motor, but you would need the exact nameplate to confirm.

Applying 115% 14 amps 1.15 = 16.1 amps. The 20 amp breaker exceeds this. Since they are bypassing the VFD which had the overload protection, the 20 amp breaker will also be working as the overload protection and the 20amp breaker would be beyond the allowed percentages according to NEC 430.32(A)(1). The best solution would be to install fuses to protect from overload with the appropiate size.
4. Short-Circuit and Ground-Fault Protection (NEC 430.52)

This protects the circuit from faults, not overloads. The 20 amp breaker provides this protection. The maximum rating or setting of the breaker depends on the motor type (Table 430.52). For a standard motor, the maximum is typically 250% of the motor FLC (Table 430.250). 250% of 16.7 amps = 41.75 amps. The 20 amp breaker is less than this, so it's acceptable for short-circuit/ground-fault protection. However, if you increase the breaker to a larger size for overload protection, you must be aware of the increase in risk of a ground fault or short circuit.5.

Fused Disconnect (NEC 430.109(A))

You mentioned a 15 amp fused disconnect. Since they are bypassing the VFD, that fused disconnect is in the circuit so you will still need to comply with the overload rules. It is currently feed a 20amp breaker. So the 15amp fuses are blowing. Based on NEC 430.32 and a nameplate of 14 Amps, your overload fuses should not exceed 16.1 Amps. If you change the fuses to comply, there would likely be nuisance tripping. It might be best to bypass both the vfd and fused disconnect and replace the 20 amp breaker with fuses. That way you can install the proper fuses, and they will be properly protected.

Your Concerns & Calculations



You are absolutely right to question using #14 wire. It's almost certainly too small and dangerous. Bypassing the VFD is generally a bad idea due to loss of protection and control. Your calculations are generally correct. You understand the difference between FLC and FLA.

Recommendations


Do NOT bypass the VFD if possible. Repair or replace it. The VFD provides valuable overload protection, adjustable speed control, and often energy savings.2. If the VFD must be bypassed



Replace the #14 wire with properly sized conductors. Use Table 310.16 to determine the correct ampacity based on insulation type, installation method, and ambient temperature. #12 AWG copper is a good starting point for a 20 amp circuit. Provide proper overload protection. Since the VFD is gone, you'll need a separate overload relay or properly sized fuses. A correctly sized thermal overload relay is the ideal solution. Keep the 20 amp breaker for short-circuit/ground-fault protection. This is likely acceptable. Verify the disconnect switch's rating. Ensure it's rated for the motor horsepower and voltage. If not, replace it.3. Consult with a qualified electrician. This is not a situation to DIY without expert help. An electrician can properly assess the situation and ensure a safe and code-compliant installation.4. Document Everything! Keep a clear record of the changes made, the reasoning behind them, and the code sections followed.

Why is this important? Safety

Undersized conductors and inadequate overload protection can lead to overheating, insulation breakdown, fires, and motor damage.

Code Compliance

Failure to comply with the NEC can result in fines, insurance issues, and liability.

Motor Life: Proper protection extends the life of the motor.I hope this helps! Don't hesitate to ask if you have more questions. Flag for review