Metal-Fach SEG BIO, Technical-Operating Documentation, Page: 29 / 64

METAL-FACH Heating Technology
27
Requirements for the expansion vessel
(Installer)
Each open system heating system must be fitted with an expansion vessel whose function is to take up the
increase in volume of the water filling the system and to vent it. This vessel should be installed at the highest
point of the system, if possible in a vertical line above the boiler(s).
The volume of the expansion vessel can be estimated by assuming a unit capacity per kW of heat output of 1-2
dm
3
.
The expansion vessel is equipped with a connection for an ascending safety pipe, a descending safety pipe, and
an overflow pipe and associated venting.
The diameter of the vent pipe and overflow pipe shall be at least:
[mm]
- boiler performance [kW]
The most important requirements for safety devices are as follows:

the expansion vessel should have a volume of approximately 3.5% of the volume of water contained in
the heating system including the boiler,

each boiler should absolutely have a safety pipe and an overflow pipe,

the system should be equipped with a signalling and expansion pipe and a venting stub for the
expansion vessel.
If several boilers are placed, each of them should be equipped with a safety pipe according to the given rules
according to PN-91/B02413 - protection of open system water heating installations. No shut-off valves must be
fitted on the safety and overflow pipes, and the pipes and vessel must be protected against freezing.