Expansion Vessels - Viessmann VITODENS 200-W Technical Manual

Design information
Even with condensing boilers, connect underfloor heating systems and
heating circuits with a very large water content (>15 l/kW) to the boiler
via a 3-way mixer; see technical guide "Control of underfloor heating
systems" or the relevant sample applications.
Install a temperature limiter in the flow of the underfloor heating circuit
to restrict the maximum temperature. Observe the requirements of DIN
18560-2 [or local regulations].
Plastic pipework for radiators
We also recommend the installation of a temperature limiter to restrict
the maximum temperature of plastic pipes in heating circuits with radi-
ators.
Safety valve
A safety valve in accordance with TRD 721 is part of the heating circuit
connection set (accessory) (opening pressure 4 bar).
Route the discharge pipe in accordance with EN 12828 into a drain
outlet (drain outlet kit available as an accessory). The drain outlet
incorporates a siphon as a stench trap.
Low water indicator
According to EN 12828, a low water indicator can be omitted for boilers
up to 300 kW, as long as heating can be reliably prevented when there
is a water shortage.
Viessmann Vitodens boilers are equipped with a low water indicator
(boil-dry protection). Tests have verified that the burner will be auto-
matically switched off in the event of water shortage due to a leak in
the heating system and simultaneous burner operation, before the
boiler or the flue system reach unacceptably high temperatures.
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Attic heating centre
The installation of a low water indicator specified as compulsory to EN
12828 is not required when installing the Vitodens in an attic heating
centre.
The Vitodens condensing boilers are protected against water shortage
in accordance with EN 12828.
Water quality/Frost protection
Unsuitable fill and top-up water increases the level of deposits and
corrosion and may lead to boiler damage.
Observe VDI 2035 regarding quality and amount of heating water, incl.
fill and top-up water.
■ Flush the heating system thoroughly before filling.
■ Only fill with water of potable quality.
■ Fill and top-up water with a water hardness in excess of the following
values must be softened, e.g. with the small softening system for
heating water (see the Viessmann Vitoset pricelist):
Total permissible hardness of the fill and top-up water
Total heating Specific system volume
output
kW < 20 l/kW
≤ 50
≤ 3.0 mol/m
(16.8 °dH)
> 50 to ≤ 200 ≤ 2.0 mol/m
(11.2 °dH)
> 200 to
≤ 1.5 mol/m
≤ 600
(8.4 °dH)
> 600 < 0.02 mol/m
(0.11 °dH)

Expansion vessels

In accordance with EN 12828, water heating systems must be equip-
ped with a pressure expansion vessel.
VIESMANN
44
(cont.)
≥ 20 l/kW to ≥ 50 l/kW
< 50 l/kW
3 3
≤ 2.0 mol/m < 0.02 mol/m
(11.2 °dH) (0.11 °dH)
3 ≤ 1.5 mol/m 3 < 0.02 mol/m
(8.4 °dH) (0.11 °dH)
3 3
≤ 0.02 mol/m < 0.02 mol/m
(0.11 °dH) (0.11 °dH)
3 < 0.02 mol/m 3 < 0.02 mol/m
(0.11 °dH) (0.11 °dH)
■ For systems with a specific system volume in excess of 20 litres/kW
heating output, use the output of the smallest boiler in multi boiler
systems.
■ An antifreeze additive 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 noise during heating operation. Viessmann accepts no lia-
bility for resulting damage or consequential losses.
When engineering the system, observe the following:
■ Install shut-off valves in the different sections. This prevents the
need for draining all the heating water in the case of repairs or sys-
tem expansion.
■ In systems > 50 kW, install a water meter to record the volume of
the fill and top-up water. Record the amount of water filled into the
system and the water hardness.
Operating information:
■ Commission the system step by step, starting with the lowest boiler
output and a high heating water flow rate. This prevents a localised
concentration of limescale deposits on the boiler heating surfaces.
■ In multi boiler systems, start all boilers simultaneously to prevent the
entire limescale deposit settling in the heat transfer area of just one
boiler.
■ During extension or repair work, only drain the necessary pipework
sections.
■ Where water treatment is required, treat even the first fill of the heat-
ing system prior to commissioning. This also applies to any subse-
quent filling, e.g. after repairs or after system expansion, and for all
amounts of top-up water.
■ Check, clean and activate filters, dirt traps and other blow-down or
separating facilities in the heating water circuit more frequently after
commissioning or new installations, later on do so subject to require-
ments in line with the water treatment applied (e.g. water softening).
Installation examples
For installation examples for the Vitodens 200-W, see "System exam-
ples".
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3
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The size of the expansion vessel is subject to the heating system
specification and should be checked in each case.
VITODENS 200-W