Yes, there would be issues feeding a buck booster with a multi-wire circuit with 3 phases and a neutral. The buck booster is not designed to operate with a multi-phase power source. Connecting it to a multi-phase circuit can cause damage to the buck booster and the power source. Additionally, the buck booster may not be able to provide the desired output voltage when connected to a multi-phase circuit.To safely use a buck booster, it should be connected to a single-phase power source. The input voltage should meet the buck booster's specified input voltage range. Using the buck booster with a voltage outside of the specified range can cause damage to the buck booster.If you need to boost the voltage from 208V to 240V, you should use a transformer. Transformers are designed to convert voltage between different levels and can be used with both single-phase and multi-phase power sources. Flag for review