This is the fan motor for the 40H series (outdoor mount) water heater. It can be used with either the natural gas (NG) or liquid propane (LP) version. It is used to blow any/all emissions through your ventilation system.
With a properly sized Eccotemp tankless water heater, you will never run out of hot water and significantly reduce your energy consumption. Eccotemp tankless water heaters are the future of efficiency.