Air Venting, Compensation, System Separation - eta SH Installation Manual

Initial protection with corrosion inhibitors
These agents line the new and still uncoated
internal surfaces with a protective film; this is only
possible in a new system. If corrosion has already
begun, these agents cannot help anymore. Use
corrosion inhibitors sparingly. For systems with
buffers whose water volume is large in relation
to the internal surfaces, it is preferable to use half
rather than double the quantity specified by the
manufacturer.
Protection against atmospheric corrosion
To reliably protect the entire heating system
against corrosion, air intrusion should be kept to a
minimum and any air that does gain entry must be
released as soon as possible. The most important
measures are described below.
Air vent at highest point in flow
No system is completely airtight. Air that gets into
the system is transported to the boiler with the
return flow since water can take up more air as it
gets colder and as the pressure increases. The air is
released again at the point in the system with the
highest temperature and the lowest pressure. The
two typical points for releasing gases are the hot
boiler and the highest point in the flow.
Install an air valve at the upper end of the line
from the boiler outlet (already installed in PU and
PC boilers) and also at the highest point in the flow
of the entire system. The boiler safety groups with
horizontal connection to the ascending flue pipe,
which have unfortunately become so common, are
not suitable for air venting.
For large, unseparated underfloor heating systems,
an absorption filter for the entire water flow
should be installed in the flow after the boiler
(Spirovent, Flamco or Pneumatex are typical
manufacturers).
At least 10% compensating volume
To minimise air suction through the system's
pipe connections (which are watertight but not
absolutely airtight) when the system cools, a
sufficiently large expansion tank with at least 10%
of the system volume is needed.
SH Montage

Air venting, compensation, system separation

Protect the expansion tank against shut-off
All shut-off valves along the path from the
expansion tank to the boiler and to the buffer
storage tank must be capped valves, or the hand
wheels or levers must be removed from the valves
(hang on the valve with a wire) to ensure that they
cannot be closed by accident.
Adjust expansion tank pressure
Most expansion tanks are delivered with primary
pressure of 1.5 bar. The pressure should be adjusted
by releasing nitrogen so that it is 0.3 bar higher than
the static pressure at the place of installation, but
the pressure should not fall below 0.9 bar.
Example 1:
height difference between expansion tank and
highest point in the system p st = 11 m = 1.1 bar:
1.1 bar + 0.3 bar = 1.4 bar pressure setting.
In this case, you can also contact our customer
service to set the system's cut-off pressure to
1.5 bar.
Example 2:
height difference between expansion tank and
highest point in the system p st = 5 m = 0.5 bar:
0.5 bar + 0.3 bar = 0.8 bar -> 0.9 bar pressure
setting.
Here the minimum pressure of 0.9 bar must be
chosen. The factory setting of 1.0 bar for the cut-off
pressure is compatible with this minimum pressure
setting.
No open expansion tanks
Open expansion tanks allow air into the system -
not allowed.
Impermeable plastic tubing
or system separation
"Impermeable" plastic tubing simply undercuts
a standard limiting value; there is no absolutely
impermeable tubing. Even composite tubing with
aluminium sheathing is not absolutely impermeable.
A rule of thumb: up to 3,000 running metres of
underfloor heating pipe, use impermeable composite
tubing; for larger systems, system separation with a
heat exchanger is imperative. If a system separation
is installed, then common single-wall tubing can
also be used. For older underfloor heating systems,
always install a system separation because their
tubing is not very airtight.
15
2012-11