Maintenance; Maintenance Intervals; Maintenance Work; Testing The Pressure Relief Valve - Bosch W 120-5 P Series Installation And Maintenance Instructions For The Contractor

9

Maintenance

▶ Allow the DHW cylinder to cool down sufficiently before performing
any maintenance.
▶ Carry out cleaning and maintenance procedures in the specified
intervals.
▶ Remedy all faults immediately.
▶ Only use original spare parts!
9.1

Maintenance intervals

Maintenance must be carried out in accordance with flow rate, operating
temperature and water hardness ( Tab. 8, page 37).
The use of chlorinated potable water or a water softener unit reduces the
maintenance intervals.
Water hardness in °dH
Calcium carbonate concentration
in mol/ m³
Temperatures
At a standard flow rate (< cylinder capacity/24 h)
< 60 °C
60 – 70 °C
> 70 °C
At a higher flow rate (>cylinder capacity/24 h)
< 60 °C
60 – 70 °C
> 70 °C
Table 8 Maintenance intervals in months
You can check the local water quality with your water supply utility.
Depending on the composition of the water, it can make sense to deviate
from the reference values listed.
W 120-5 P | W 160-5 P | W 200-5 P | W 200-5 EP – 6 720 821 084 (2018/10)
3 – 8.4 8.5 – 14 > 14
0.6 – 1.5 1.6 – 2.5 > 2.5
Months
24 21 15
21 18 12
15 12 6
21 18 12
18 15 9
12 9 6
9.2

Maintenance work

9.2.1

Testing the pressure relief valve

▶ Check the pressure relief valve annually.
9.2.2

Descaling/cleaning the DHW cylinder

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 DHW cylinder on the domestic hot water side from the
piping.
▶ Close the shut-off valves and isolate the immersion heater (if used)
from the mains power supply. ( Fig. 17, page 64).
▶ Drain the DHW cylinder ( Fig. 15 and 16, page 64).
▶ Check the DHW cylinder interior for contamination (limescale,
sediment).
▶ In the case of soft water:
Check the cylinder interior regularly and clean out any sediment
deposits.
-or-
▶ In the case of hard water or severe contamination:
Regularly descale the DHW cylinder in line with the actual amount of
limescale using chemical cleaning methods (e.g. with a suitable
descaling agent based on citric acid).
▶ Clean out the DHW cylinder interior with a water jet
( Fig. 21, page 65).
▶ Use a wet & dry vacuum cleaner with plastic suction hose to remove
residues.
▶ Close the inspection aperture with a new gasket
( Fig. 24, page 66).
▶ Re-commission the DHW cylinder ( Chapter 6, page 7).
9.2.3

Checking the magnesium anode

The DHW cylinder warranty is void if the magnesium
anode is not correctly maintained.
The magnesium anode is a sacrificial anode, which is used up when the
DHW cylinder is in operation.
We recommend that the protection current is measured annually using
an anode tester ( Fig. 19, page 65). The anode tester is available as
an accessory.
Never bring the magnesium anode surface into contact
with oil or grease.
▶ Keep everything clean.
▶ Shut off the cold water inlet.
▶ Depressurise the DHW cylinder ( Fig. 15, page 64).
▶ Remove and test the magnesium anode ( Fig. 20 to Fig. 24,
page 65 and page 66).
▶ Replace the magnesium anode if its diameter has been reduced to
less than 15 mm.
▶ Check the transfer resistance between the protective conductor
connection and the magnesium anode.
Maintenance
37