Hydraulic Connection - Viessmann VITODENS 200-W Technical Manual

Design information

4.3 Hydraulic connection

General information
System design
Viessmann condensing boilers can generally be installed in any fully
pumped hot water heating system (sealed unvented system).
Connection sets with an integral circulation pump are available as
accessories.
Minimum system pressure 1.0 bar (0.1 MPa).
The boiler water temperature is limited to 82 ºC.
To keep distribution losses as low as possible, we recommend sizing
the heat distribution system for a maximum flow temperature of
70 °C.
Chemical anti-corrosion agents
In correctly installed and operated sealed unvented heating systems
corrosion is generally avoided.
Never use chemical anti-corrosion additives.
Some manufacturers of plastic pipes recommend the use of chemical
additives. In such cases, only use anti-corrosion additives offered by
the heating trade that have been approved for boilers with DHW heat-
ing via single-walled heat exchangers (instantaneous water heater or
DHW cylinder).
For this, observe the VDI guideline 2035 [or local regulations].
Heating circuits
For heating systems with plastic pipes, we recommend the use of
impermeable pipes to prevent the diffusion of oxygen through the pipe
4
walls.
Provide system separation in heating systems with plastic pipes that
are permeable to oxygen (DIN 4726). A separate heat exchanger for
this purpose is available.
Install a dirt separator in underfloor heating systems. See Viessmann
Vitoset pricelist.
Underfloor heating systems and heating circuits with very large water
content (>15 l/kW) should be connected to the condensing boiler via
a 3-way mixer. See technical guide "Control of underfloor heating sys-
tems" 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 use of a temperature limiter to restrict the
maximum temperature for plastic pipework in heating circuits with radi-
ators.
Safety valve
A safety valve in accordance with TRD 721 is part of the heating circuit
connection set (accessories) (opening pressure 4 bar) (0.4 MPa).
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 condensing 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 reaches unacceptably high temperatures.
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.
VIESMANN
46
(cont.)
Water quality/Frost protection
Unsuitable fill and top-up water increases the level of deposits and
corrosion and may lead to the boiler damage.
Observe VDI 2035 regarding quality and amount of heating water,
including 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
≤ 3.0 mol/m
(16.8 °dH)
> 50 to ≤ 200
≤ 2.0 mol/m 3
(11.2 °dH)
> 200 to 3
≤ 1.5 mol/m
≤ 600
(8.4 °dH)
> 600
< 0.02 mol/m 3
(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.
■ Antifreeze suitable for heating systems can be added to the fill water.
The antifreeze manufacturer must verify its suitability, since other-
wise damage to gaskets and diaphragms can occur as well as noise
during heating operation. Viessmann accepts no liability for any
resulting damage or consequential losses.
When designing 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 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 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 expansion 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. when adding top-up water or after a repair, or for
any system expansion.
■ Check, clean and activate filters, dirt traps and other blow-down or
separating facilities in the heating water circuit more frequently after
the commissioning or in case of new installations, later on subject to
the water treatment applied (e.g. water softening).
Installation examples
For installation examples for the Vitodens 200-W, see "System exam-
ples".
≥ 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)
≤ 1.5 mol/m 3 < 0.02 mol/m 3
(8.4 °dH) (0.11 °dH)
3 3
≤ 0.02 mol/m < 0.02 mol/m
(0.11 °dH) (0.11 °dH)
< 0.02 mol/m 3 < 0.02 mol/m 3
(0.11 °dH) (0.11 °dH)
VITODENS 200-W