When designing the system, observe the following:
■ Install shut-off valves in each section. This prevents the need for
draining all the heating water in the case of repairs or system
expansion.
■ Install a water meter to record the volume of fill and top-up water.
The volumes and hardness of the topped-up water volumes must
be entered in the boiler service instructions.
■ For systems with a specific volume greater than 20 litres/kW heat-
ing output (for multi boiler systems, the output of the smallest
boiler should be used), the requirements of the next highest total
heating output group should be applied (using the table). If even
bigger (> 50 litres/kW), soften the water down to a total of alkaline
earths of ≤ 0.02 mol/m
3
.
Operating information:
■ Start the system gradually at a high heating water flow rate, start-
ing with the lowest boiler output. This prevents localised concen-
tration of limescale deposits on the heating surfaces.
■ For multi boiler systems, all boilers should be started at the same
time to prevent the entire volume of limescale settling on the heat
transfer surface of only one boiler.
■ During expansion or repair work, only drain the necessary sec-
tions.
■ Where water treatment is required, treat even the first fill of the
heating system prior to commissioning. This also applies to any
subsequent filling, e.g. when adding top-up water or after a repair,
or for any system expansion.
■ Periodically inspect, clean and activate all filters, dirt traps or other
blow-down or separating facilities in the heating water circuit after
reinstalling or installing for the first time. Thereafter, this may be
one as required, depending on the type of water treatment applied
(e.g. water softening).
The build-up of limescale deposits on the heating surfaces will be
minimised if these instructions are followed.
If failure to observe guideline VDI 2035 results in harmful limescale
deposits, the service life of the installed boilers will in most cases
have already been reduced. Removing limescale deposits may be
an option to restore the operating capability. This must be carried out
by Viessmann Industrieservice or a specialist contractor. Inspect the
heating system for possible damage prior to returning it into use. The
faulty operating parameters must be corrected in order to prevent
excessive scale build-up from reoccurring.
Filling the heating system
The charge pressure of the cold hydraulic seal must be approx.
0.1 bar (0.01 MPa) higher than the pre-charge pressure of the
sealed expansion vessel. However, it must not exceed a maximum
of 3 bar (0.3 MPa).
9.13 Frost protection
Special antifreeze suitable for heating systems can be added to the
fill water. The antifreeze manufacturer must verify its suitability, since
otherwise damage to gaskets and diaphragms can occur as well as
noisy heating operation. Viessmann accepts no liability for any
resulting damage or consequential losses.
When planning, take into account that the use of antifreeze reduces
the output of the boiler.
9.14 Connection on the flue gas side
Chimney
The system is equipped with a flue gas fan and therefore the com-
bustion equipment does not require a draught. The chimney must be
designed in the same way as for combustion equipment with a pres-
sure-jet oil or gas burner without draught requirement (flue gas tem-
perature at rated load 160 - 200 °C). The Vitoflex 300-UF has out-
put-dependent control modulating between 25 - 100 % of the rated
heating output. This results in flue gas temperatures in the range of
min. 100 °C up to max. 250 °C. In order to avoid a risk of soot con-
tamination, there should be an insulated chimney. The route from the
flue gas fan to the chimney should be as short as possible. If at all
possible, avoid 90° bends in the flue system. Flue pipes over 1 m
long must be thermally insulated. The connection to the chimney
should be made with a rise at an angle of 30 - 45°. The flue pipe,
including the inlet to the chimney, must be gas-tight.
A chimney compliant with regulations relevant to the rated boiler
heating output is required for efficient boiler operation.
Provide verification to EN 13384.
Flue gas temperatures below 90 ºC can occur in the lower output
range. Therefore, connect the boiler to a
moisture-resistant chim-
ney
(thermal resistance class I according to DIN 18160 Part 1).
Note
If the boiler is
not
to be connected to a moisture-resistant chimney,
carry out a chimney calculation or request a chimney assessment
(values for a chimney calculation, see page 14).
Flue pipe
Acoustic transmission may arise from the flue gas fan, which can
lead to excessive noise. We therefore recommend making the con-
nection to the chimney with a flexible flue pipe inlet.
Design information
(cont.)
96
Viesmann
VITOFLEX 300-UF
9
5682428
