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321 - Heating Filling Unit according to VDI 2035


The heating systems have become in recent years more compact; smaller heat exchange surfaces can offer today much higher performance than before. This makes them however more subject to malfunction. If the heating system operates with inadequate water quality the consequences are: corrosion, lime deposits, sludge and air in the system.
For this reason heating systems are to be filled and shall work with soft water, according to the VDI 2035 regulations.
Thanks to a mixture of selected ion exchange resins and a pH stabilizer in the first filling operation, the water is largely demineralized (>0,5°dH) and alkalized to pH values between 8.2 to 8.7.
As the corrosive ions, such as chloride and sulfate, are also removed, a better protection against corrosion is provided without the help of chemical inhibitors. At the same time water conductivity is reduced.

Consisting of:

Heating filling unit complete with filling assembly and backflow preventer Type BA, Fig. 305K
Heating demineralization unit complete with water meter, cartridge with capacity 4000° dH x Liter

Connections 1/2” - 3/4”

Brass body

For the fixing of the unit on the wall we provide a mounting bracket on demand.

Screws and plugs not included.




Dimensions in mm


321.K -  Cartridge for the heating filling unit

321.VE -Heating Filling Set

Heating filling unit (without filling assembly Fig. 305.K) equipped with:

Water meter, Fig. 568
Cartridge for the heating filling unit, Fig. 321.K
Two shut-off valves, Fig. 583





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