eta PelletsCompact Installation Manual Download

Page: 24 / 68

www.eta.co.at

Corrosion

Information for installation

Lime stabilisation can be dangerous

The  addition  of  lime  stabilising  agents  prevents
limescale.  However,  we  advise  against  doing  this.
These agents increase the salt content and result in an
undefined  pH  value.  If  the  system  is  filled  with  large
amounts  of  water,  exactly  the  same  agent  must  be
used again. Mixing with other water additives or with
antifreeze can result in corrosion.

7.4

Corrosion

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  can  no  longer  be  of  help.  Use  corrosion
inhibitors sparingly.
For  systems  with  buffers  with  a  large  water  volume
relative to the internal surfaces, it is preferable to use
half  rather  than  double  the  quantity  specified  by  the
manufacturer.

7.5

Bleeding

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.

Bleeding 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 gas are the hot boiler and the highest point in
the heating system flow.

Install a bleed valve at the upper end of the pipe from
the boiler outlet (already installed in PelletsUnit and
PelletsCompact boilers) and also at the highest point in
the flow of the entire system.

Fig. 7-5: correct positioning of the bleed valve

The T-piece of the bleed valve must be the same
size as the boiler's flow connection, so that no air

pocket may form. Likewise, the boiler body must be
oriented horizontally, or ascending slightly toward the
flow connection, so that air can escape.
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
and Pneumatex are typical manufacturers).

Impermeable plastic tubing or system separation

Plastic tubing which is used must have DIN 4726 cer-
tification. As a rule, this is documented with a DIN test
mark  and  a  register  number  in  the  pipe  label.
Underfloor  heating  systems  from  older  construction
years often do not meet the requirements of the DIN
standard from 1988. A considerable input of oxygen is
to be expected here. The oxygen introduced can have
a corrosion-promoting effect on various components in
the  heating  system.  A  separation  of  the  existing
underfloor heating from the new boiler is required here.
Although the limit values are not reached, the sum of
the oxygen input via surface heating system, distribu-
tion,  leakages,  replenishment,  etc.  can  also  cause
corrosion  damage,  especially  in  large  systems  (pipe
lengths over 5000 running metres). A separation of the
surface  heating  system  from  the  heating  boiler  is