Solar System Design Guide
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Design and Operation
System for Heating DHW
DHW heating in detached houses can be realized either
with one dual coil solar DHW tank or with one single coil
(for retrofitting an existing system) solar tank preheating
the water prior to the auxiliary DHW tank.
Examples
: For further detailed examples, see the "Sample
Piping Layout Drawings” manual, available for
download from the Viessmann website.
Single coil
The basis for sizing a solar thermal system for DHW
heating is the DHW demand. Viessmann solar packages
are sized for a solar coverage up to 60%. The tank
capacity must be greater than the daily DHW demand,
taking the required DHW temperature into account.
To achieve solar coverage of approximately 60%, the
collector system must be sized so that the entire tank
capacity can be heated on a single sunny day (5 hours
of full sunshine) to at least 140°F (60°C) . This would
enable poor insolation the following day to be bridged.
System with a dual coil DHW tank
System with single coil and a direct fired DHW tank
System with two single coil DHW tanks
