Airflow Pre Post Heater for DV250 DV400 700W 990 322 051 F7 Filters are fine grade F7 Filters are fine grade and designed to capture small and often invisible particles such as pollen spore Nominal duct diameter 125 mm Operating height 470 mm With roof flashing Yes With pre mounted seal No Surface treatment cap Coated Vertical exhausting Yes Material of cap Steel Connection Duct end Lead flashing on all sides Yes Lamella model No Colour cap Red With storm collar No Suitable for suction Yes With gauze No Cover outer diameter 215 mm Material roof flashing Other Free passage 0 The optional additional heater (700W) can be used pre or post the heat recovery unit (a pre heater must be used if Passive House conformance for the heat recovery unit is required) They are used to temper incoming supply air through the heat recovery unit