4 Planning and installation – Connections
23
O
PERATION
WITHOUT
AN
ACCUMULATOR
In principle the heating system HDG K10 - 33 does not need an
accumulator. This requires a guaranteed minimum heat transfer
capacity, for example, a demand circuit that cannot be disabled or no
thermostat valves on any radiator.
Exception
:
If the entire heat requirement of the object according to calculations
in accordance with DIN EN 12831 is less than 50% of the nominal
thermal power, we recommend installing an accumulator. This
means that the HDG K10 - 33 boiler charges the accumulator by
means of a return flow boost assembly.
U
SING
AN
ACCUMULATOR
When calculating the thermal requirements of buildings, e.g.
according to DIN EN 12831 “Method for calculating the normal
heating load”, the lowest outside temperature of the relevant climate
zone (e.g. -15 °C) is used. This condition only applies a few days per
year, thus, the thermal performance of the heating system is greater
than required on most days when heating is needed.
For this reason, the HDG K10 - 33 is fitted with power control as
standard and with automatic ignition.
It is, however, highly recommended to use an accumulator even
with automatic boiler systems.
The size of the accumulator will depend on the nominal thermal
power of the boiler and on the thermal requirements of the building.
As a guide, the recommended value of 20 litres per kW boiler output
can be used.
An advantage of using an accumulator lies in the lower operating
hours of the system and fewer start-up phases due to the extension
of the heating intervals. This leads to a reduction in the proportion of
external energy supplied and to lower wear of the mechanical
components.
For the above-mentioned reasons, we recommend an
accumulator even for automatic boiler systems.
S
AFETY
DEVICES
Safety devices (e.g. boiler safety module, low-water-level switch etc.)
must be installed in accordance with DIN EN 12828: “Design for
water-based heating systems in buildings”.
R
ETURN
TEMPERATURE
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
Important!
The heating system must be filled with water in accordance with
VDI guideline 2035, “Avoiding damage in hot water heating
systems”.
Antifreeze agents may only be used after prior consultation with
HDG.
