HDG Navora 20, Operation Manual

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4 Planning and installation – Connections
32
S
AFETY DEVICES
Safety devices (e.g. boiler safety module, insufficient water cutout,
etc.) must be installed in accordance with DIN EN 12828: 2003
“Design of water-based heating systems in buildings”.
R
ETURN TEMPERATURE
CONTROL
Operating temperatures which are too low significantly shorten the
service life of the boiler. Water vapour contained in the flue gas could
be released in the form of condensation if the temperature drops
below the dew point (approx. 50–55 °C), especially in the area around
the water-cooled heat-exchanger surfaces. This condensation, in
combination with combustion residue, can lead to corrosion.
For these reasons, a return temperature control must be installed for
the HDG Navora heating system. The return temperature control
causes the water from the boiler return line to be mixed with the
water from the boiler supply line until the minimum return
temperature has been reached.
✎
The minimum return temperature is listed in chapter “3 Mode of
operation”, section “3.3 Technical data”.
The control of the return temperature is handled by the HDG Lambda
Control 1 plus/2 plus control unit.
The return temperature control consists of a 3-way mixing valve with
a 230 V servo drive (running time 120-240 s) and a circulation pump.
For the HDG Navora with a nominal thermal power we recommend:
• 20/25/30 kW: Wilo 30/1-6, 3-way mixing valve DN 32
• 40/50 kW: Wilo 30/1-7, 3-way mixing valve DN 32
(or comparable)
The hydraulic system must be installed in accordance with specific
technical principles of heating engineering. Take into account the
stop cocks required for maintenance work and repairs.
The return temperature control must be installed according to the
specifications of HDG Bavaria.
Important!
Please also observe DIN EN 303-5 as well as the individual comfort
requirements of the customer for the capacity of the accumulator.
The pipe dimensions must be adapted to meet the requirements at
the site. Take the water-side connections of the boiler for the supply
and return into account.
✎
See Chapter “3 Mode of operation”, section “3.3 Technical data”.
The return temperature control is not designed for the use of a
gravity brake and this should therefore not be installed.