Stiebel Eltron WWS 20 Manuel D'utilisation Et Installation page 60

INSTALLATION
Specification
Heating the DHW cylinder via inlet connectors on the sides
Heating the DHW cylinder via the integral smooth tube indirect coil
Note
At a temperature differential of 5 K between the flow and
return, the thermal output of the heat pump (see chapter
"Specification") must be transferred via the coil.
Due to the additional heat transfer, this installation may
result in different and lower output and efficiency data.
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