Drain Work; Descaling And Cleaning; Recommissioning; Function Check - Bosch Stora WP 400 PK Installation And Service Instructions Manual

9.4.2

Drain work

▶ Disconnect the cylinder from the mains power supply and drain
before carrying out any cleaning or repairs.
▶ Drain the heat exchanger.
Blow out the lower coils if required.
9.4.3

Descaling and cleaning

In order to improve the cleaning effect, heat up the heat exchanger
prior to cleaning it with a water jet. The thermal shock effect separates
deposits (e.g. limescale) more readily.
▶ Isolate the cylinder from the piping on the domestic water side.
▶ Close the shut-off valves and isolate the immersion heater (if used)
from the mains power supply.
▶ Drain the cylinder.
▶ Open the inspection aperture on the cylinder.
▶ Check the interior of the cylinder for pollution.
-or-
▶ In the case of soft water:
Check the container regularly and clean to remove limescale.
-or-
▶ In the case of hard water or severe pollution:
Regularly descale the cylinder in line with the actual amount of
limescale using chemical cleaning methods (e.g. with a suitable
descaling agent based on citric acid).
▶ Hose down the inside of the cylinder.
▶ Use a wet & dry vacuum cleaner with plastic suction hose to remove
the residues.
▶ Use a new gasket to seal the inspection aperture.
Cylinder with inspection aperture
NOTICE
Water damage!
If the gasket is defective or corroded this could cause water damage.
▶ Check the gasket of the cleaning flange during cleaning and replace.
9.4.4

Recommissioning

▶ Flush the cylinder thoroughly after cleaning or repair.
▶ Vent on the heating side and on the domestic water side.
9.5

Function check

NOTICE
Damage through positive pressure.
A pressure-relief valve malfunction can result in damage due to positive
pressure.
▶ Check the pressure-relief valve function and flush through several
times by venting.
▶ Never close the blow-off opening of the pressure-relief valve.
Stora – 6721835341 (2021/04)
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Faults

Clogged connections
In combination with a copper pipe installation, connections may become
clogged in unfavourable conditions due to the electrochemical action
between the magnesium anode and pipe material.
▶ Use insulation fittings to electrically isolate connections
from the copper pipe installation.
Odour problems and dark discolouration of the heated water
This is normally caused by the formation of hydrogen sulphide due to
sulphate-reducing bacteria. The bacteria are present in water with a very
low oxygen content, and release the oxygen from the residual sulphate
(SO ) which produces strong smelling hydrogen sulphide.
4
▶ Clean the container, replace the anode and operate at ≥ 60 °C.
▶ If this does not effectively remedy the situation: replace the anode
with an external current anode. The user bears the costs of the
conversion.
Activation of the high limit safety cut-out
If the high limit safety cut-out in the wall mounted boiler is repeatedly
activated:
▶ Inform the installer.
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Faults
37