The E+ heater requires a three phase electrical supply. For full details please see the E+ installation manual (https://www.reznor.co.uk/wp-content/uploads/2024/08/Reznor-e-Installation-Manual-EN-2024-06-D301600-Iss-0-print-quality-1.pdf).
Does the E+ heater require any special electrical connections?
Information on Reznor's range of warm air heaters