Installation Instructions

DHW heating
6 720 645 817 (2010/09)
62
Cylinder connection on the heating side
The sizing of the connection lines for the cylinder flow
and return is based on a temperature differential of 20 K.
Table 35 shows the resulting internal diameters. When
using flexible connection lines, such as corrugated
stainless steel hoses, apply a higher pressure drop than
for rigid pipework.
To prevent unnecessary pressure drop and cylinder
cool-down through pipe circulation, keep primary lines
as short and well insulated as possible.
Generally the cylinder return is connected near the cold
water inlet. This means that the DHW cylinder operates
in countercurrent mode. As a result, the heat input is
optimally transferred.
If required, provide a heating time control (Æ heating
controls).
Provide an effective means of venting (e.g. air separator)
at the highest point between the cylinder and the boiler
to prevent operating faults through air locks.
The DHW cylinder can cool down in summer mode
through gravity circulation. To prevent this, install a
non-return valve or check valve in the cylinder return.
Mixed installation
According to DIN 1988, the installation of a nonferrous
heavy metal fitting is adequate to protect materials with
different potentials, such as stainless steel and
zinc-plated steel, against electrochemical corrosion. In
such cases (this also includes DHW cylinders made from
enamelled steel) adaptor fittings made from red bronze
have often been used.
However, the most recent experiences with DHW with
high conductivity and a high level of hardness (> 15 °dH)
have shown that there is still a risk of corrosion forming
at the adaptor point, even when red bronze fittings are
used. Furthermore, in these areas incrustations were
discovered that in some cases result in a complete
closure of the pipe cross-section. For such mixed
installations in accessible areas, we therefore
recommend the use of insulation fittings as a suitable
solution.
Cylinder
Recommended internal
diameter of the connection lines
SK 300-3 ZB DN 25
SK 400-3 ZB DN 32
SK 500-3 ZB DN 32
SK 800-ZB DN 65
SK 1000-ZB DN 65
SE 300-1 DN 25
Tab. 35
The following section only applies to
enamelled DHW cylinders, not stainless
steel cylinders SE 300-1.