To prevent heat accumulation, no warm air outlets or warm air ducts must be closed off on the Combi 6 (E).
With the Combi 4 (E) no more than one warm air outlet or warm air duct may be completely closed off. But it is always better to use all four warm air outlets. Individual outlets in the same pipe may be closed only if T/Y-pieces are used and the heat can be directed to another open warm air outlet.