Hydraulic Connection; General Information - Viessmann VITODENS 300-W Technical Manual

Design information
(cont.)

6.6 Hydraulic connection

General information

System design
Viessmann condensing boilers can generally be installed in any fully
pumped hot water heating system (sealed unvented system).
The circulation pump is an integral part of the appliance.
Minimum system pressure 1.0 bar (0.1 MPa).
The boiler water temperature is limited to 82 °C.
To minimise distribution losses, we recommend sizing the heat distri-
bution system to a max. flow temperature of 70 °C.
For apartments with less than 80 m
houses with low heat demand we recommend, due to the immediate
capturing of the room-influencing factors, using the Vitodens with a
constant temperature control unit in conjunction with the Vitotrol 100.
To reduce burner cycling in low energy houses with a correspondingly
low heat demand, we recommend the use of a low loss header or a
Vitodens 300-W with 1.9 to 11 kW.
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 agents offered by the
heating trade that have been approved for boilers with DHW heating
via single-walled heat exchangers (instantaneous water heater or
DHW cylinder).
For this, observe the VDI Directive 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
walls.
Provide system separation in heating systems with plastic pipes
(DIN 4726) that are permeable to oxygen. We supply a separate heat
exchanger for this purpose.
Install a dirt separator in underfloor heating systems; see the
Viessmann Vitoset pricelist.
Underfloor heating systems and heating circuits with very large water
content (>15 l/kW) should be connected to the boiler, even if a con-
densing 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 for plastic pipes in heating circuits with
radiators.
Attic heating centre
The installation of a low water indicator specified as compulsory by
DVGW is not required when installing the Vitodens in an attic.
The Vitodens condensing boilers are protected against water shortage
in accordance with EN 12828.
Safety valve
A safety valve in accordance with TRD 721 is integrated in the
Vitodens (opening pressure 3 bar (0.3 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.
VITODENS
2
living space or for low energy
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 reaches unacceptably high temperatures.
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, 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
≤ 3.0 mol/m
(16.8 °dH)
> 50 to ≤ 200 ≤ 2.0 mol/m 3
(11.2 °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,
otherwise damage to gaskets and diaphragms may occur, as well
as noise during heating operation. Viessmann accepts no liability for
any 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 of the heating water in the case of repairs or
system 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).
Modernising existing systems
Third party appliance adaptors are available as accessories for the
Vitodens 200-W and 300-W.
≥ 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)
VIESMANN
75
6