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Pre-Installation
4.2
Mains supply
4.2.1
Electrical supply
• There must be two electrical supplies to the appliance: control unit
and heater. It must be possible to isolate each supply.
• Supply: 230V AC - 50 Hz (each)
• This product must not be connected to a three phase supply.
• The wiring between the product and the electrical supply must
comply with the latest IET wiring regulations that apply to wiring to
Class 1 fixed equipment.
• The appliance incorporates low energy DC modulating pumps. If an
RCD is required, it must be minimum type A. Type AC must not be
used. This applies only to the control unit (not the heater).
• The product must be earthed.
• Cable 1 (control unit): Heat resistant PVC 3-core flexible cable
2
1.0mm
to H05V2V2-F.
• Cable 2(heater): Heat resistant PVC 3-core flexible cable 2.5mm
H05V2V2-F.
• Additional equipment wired to the product must comply with the
latest IET wiring regulations.
4.2.2
Explanations for the hydraulic configuration
General
XCU-THH (XCU
Installer module integrated into the indoor unit
HY)
UI800
User interface
CR10
Room controller (accessories)
T1
Outside temperature sensor
PW2
DHW circulation pump (accessories)
TW1
DHW temperature sensor
Heating circuit without mixing valve
PC1
Circulation pump for heating circuit
MC1
Safety thermostat
4.3
Water quality
4.3.1
Quality requirements for the heating water
The quality of the fill and top-up water is an essential factor for increased
efficiency, functional reliability, long service life and for maintaining the
operational readiness of a heating system.
Unsuitable water can damage the heat exchanger or cause a fault in the
heat generator or DHW supply!
Unsuitable or contaminated water can lead to sludge formation,
corrosion or scaling. Unsuitable antifreeze or hot water additives
(inhibitors or anti-corrosion agents) can damage the heat generator and
heating system.
▶ Only fill the heating system with potable water. Do not use well or
groundwater.
▶ Determine the water hardness of the filling water, before filling the
system.
▶ Flush the heating system prior to filling.
▶ If magnetite (iron oxide) is present, anti-corrosion measures are
required and the installation of a magnetite separator and a de-airing
valve in the heating system is recommended.
▶ The limit values in table 3 must not be exceeded, even if national
directives contain higher limits.
12
Water quality
Conductivity
pH
Chloride
Sulphate
Sodium
Table 3 Boundary conditions for potable water (filling water)
▶ Check the pH value after > 3 months of operation. Ideally at the first
service.
Material of heat
generator
Copper brazed
heat exchangers
2
• Low-salt operation < 100 μS/
to
1) If pH value is < 8.2 an on-site test for ferrous corrosion is necessary
Table 4 pH value ranges after > 3 months of operation
▶ Treat the fill and top up water according to the instructions in the
following section.
Depending on the hardness of the filling water, the system water volume
and the maximum heat output of the heat generator, water treatment
may be required to avoid a damage in water heating installations, due to
the formation of lime scale.
Requirements on the fill and top-up water
3,00
2,80
< 100 kW
2,60
< 50 kW
2,40
2,20
2,00
1,80
y
1,60
1,40
1,20
1,00
0,80
0,60
0,40
0,20
0,00
0
5
Fig. 14 Heat generators < 50 kW-100 kW
[x]
Total hardness in °dH
[y]
Maximum possible water volume over the service life of the heat
3
source in m
[1]
Above the curve, only use desalinated fill and top-up water, with a
conductivity of ≤ 10 μS/cm
[2]
Below the curve, untreated fill and top-up water according to
drinking water regulation can be used
Unit
Value
μS/cm
≤ 2500
≥ 6,5... ≤ 9,5
ppm
≤ 250
ppm
≤ 250
ppm
≤ 200
Heating water
•Untreated potable water
•Fully softened water
cm
1
2
10
15
20
x
Pre plumbed cylinder – 6 721 852 928 (2023/04)
pH value range
1)
7.5
– 10.0
1)
7.0
– 10.0
25
30
0010048707-001
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