7
Inspection and servicing
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7
Inspection and servicing
▶ Let the DHW cylinder cool down sufficiently prior to any maintenance
work.
▶ Carry out cleaning and maintenance procedures at the specified
intervals.
▶ Remedy all faults immediately.
▶ Only use genuine spare parts.
7.1
Inspection
An inspection of DHW cylinders must be carried out every 2 months in
accordance with DIN EN 806-5. During this the set temperature should
be checked and compared with the actual temperature of the heated
water.
7.2
Service work
Annual maintenance should be carried out in accordance with
DIN EN 806-5, Appendix A, tab. A1, line 42. This includes the following
work:
• Functional check of the pressure relief valve
• Leak test of all connections
• Cleaning of the cylinder
• Checking of the anode
7.3
Maintenance intervals
Maintenance must be carried out based on the flow rate, operating
temperature and water hardness (
tab. 9). Based on our many years
of experience, we recommend that service intervals are selected
according to tab. 9.
The use of chlorinated potable water or a water softener unit reduces the
service intervals.
You can check the water quality with your water supply utility.
Depending on the composition of the water, it may be sensible to deviate
from the indicated values given.
7.4
Maintenance work
7.4.1
Checking the pressure relief valve
▶ Check the pressure relief valve annually.
7.4.2
Descaling/cleaning the DHW cylinder
▶ Disconnect the DHW cylinder on the potable water side from the
mains.
▶ Close the shut-off valves and isolate the immersion heater (if used)
from the mains power supply (
▶ Drain the DHW cylinder (
▶ Open the inspection port on the cylinder (
▶ Inspect the interior of the DHW cylinder for contamination (limescale
deposits).
-or-
▶
In the case of soft water:
Check the tank regularly and clean out any limescale 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
(
▶ Use a wet/dry vacuum appliance with a plastic suction pipe to
remove any residues.
▶ Close the inspection port using a new gasket (
▶ Re-commission the DHW tank (
7.4.3
Checking the magnesium anode
We recommend that the protection current is measured annually using
an anode tester (
Fig. 41, page 75). The anode tester is available as
an accessory.
Testing with the anode tester
There must be an insulated installation of the magnesium anode when
using an anode tester to measure the protection current
(
The protection current can only be measured if the cylinder is filled with
water. Ensure that there is proper contact of the terminals. Only connect
terminals to shiny metal surfaces.
▶ Release the ground wire (contact cable between the anode and
cylinder) at one of the two connection points.
▶ Attach the red cable to the anode and the black cable to the cylinder.
▶ If the ground wire has a plug: Connect the red cable to the thread of
the magnesium anode.
▶ Remove the ground wire for the measuring procedure.
▶ Connect the ground wire correctly again after every test.
If the anode current is < 0.3 mA:
WARNING:
Risk of scalding from hot water!
▶ Let the DHW cylinder cool down sufficiently.
Water hardness [°dH]
3...8.4
8.5...14
> 14
Calcium carbonate concentration
[mol/m
3
]
0.6...1.5
1.6...2.5
> 2.5
Temperatures
Months
At a normal flow rate (< cylinder capacity/24 h)
< 60 °C
24
21
15
60...70 °C
21
18
12
> 70 °C
15
12
6
At an increased flow rate (> cylinder capacity/24 h)
< 60 °C
21
18
12
60...70 °C
18
15
9
> 70 °C
12
9
6
Table 9 Service intervals in months
In order to improve the cleaning effect, heat up the heat
exchanger prior to cleaning it with a water jet. The
thermal shock effect releases deposits
(e.g. limescale deposits) more readily.
The magnesium anode is a sacrificial anode, which is
consumed during the operation of the DHW cylinder.
The DHW cylinder warranty is void if the magnesium
anode is not correctly maintained.
Observe the operating instructions for the anode tester.
