The Helios Fans WHR 250 is a compact water heater battery designed for integration with circular duct systems. It features a durable galvanized steel housing and spigots on both ends, equipped with double lip rubber seals for a secure connection to standard nominal ducts. Inside, the unit contains copper heating elements with aluminium fins to ensure effective heat transfer. It is rated for a maximum operating temperature of 100 °C and a pressure capacity of up to 8 bar. For ease of installation and servicing, the unit includes two inspection caps on the water connection side.