4 Planning and installation – Connections
39
✎
The required connection values are described in chapter “3 Mode
of operation”, section “3.3 Technical data”.
C
ONTROL
CABINET
The HDG Control unit is located in the EMD-C 215 Exclusiv control ca-
binet. The cables are inserted from the top of the control cabinet and
the wiring is connected in accordance with the supplied circuit dia-
grams.
A
CCUMULATOR
SENSOR
The temperature sensors are immersion sensors with a moulded
cable and serve to measure the temperature of the buffer tank.
W
ATER
The heating system must be filled with water in accordance with VDI
guideline 2035, “Avoiding damage in hot water heating systems”.
U
SING
AN
ACCUMULATOR
When calculating the thermal requirements of buildings, e.g. accor-
ding 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 Compact 99 - 200 is fitted as standard with power control and
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 benchmark value, 20 litres per kilowatt boiler power can be
used. This results in a boiler burning duration of approximately one
hour at full-capacity operation, during which the accumulator is
completely filled. The emptying time of the accumulator at 25% no-
minal load amounts to 3.7 hours for this type of design, with an as-
sumed usable temperature difference of 40 Kelvin.
One advantage of a buffer tank is the low number of operating hours
for the system and fewer start phases due to extended heating pe-
riods, which leads to a reduction in the proportion of external energy
and to lower wear of the mechanical components.
One further advantage of the accumulator is in summer operation
when only hot water is required. When operating in this mode, the
accumulator helps avoid frequent ON/OFF switching.
For the above-mentioned reasons, we recommend a buffer tank
even for automatic boiler systems.
S
AFETY
DEVICES
Safety devices are to be installed in accordance with DIN EN 12828:
2003 “Design of water-based heating systems in buildings”.
Antifreeze agents may only be used after consultation with HDG.
