HDG Compact 25, Operation Manual

Page: 28 / 188

3 Mode of operation – Functional description
28
S
OLAR HEATING
-
HOT WATER
TANK
/
ACCUMULATOR
/
HEAT
EXCHANGER
The criteria for switching between hot water heating and accumu-
lator heating are identical to that for “Solar heating - hot water tank /
accumulator”. The difference lies only in that for hot water heating,
only the hot water heating pump is triggered, and for accumulator
heating, the hot water heating pump, changeover valve and accu-
mulator heating pump are triggered.
✎
See the informational booklet “Hydraulic solutions of the HDG Hy-
dronic”, section “Hydraulic system 4.S”.
P
ROTECTING THE COLLECTOR
FROM OVERHEATING
This function is only active when solar heating is being used for the
hot water tank or for the combination accumulator. If the protection
temperature for the solar collector (
Solar 18-12
parameter), fac-
tory setting 110 °C, is exceeded, the solar pump will start, even if the
maximum temperature for solar heating has been exceeded. This
protects the collector from overheating. See the details supplied by
the manufacturer of the solar collector for the specified protection
temperature and modify the setting accordingly.
S
PEED
-
CONTROLLED SOLAR HOT
WATER AND SOLAR
ACCUMULATOR PUMPS
The speeds of the solar pumps are calculated from the temperature
difference between collector and tank, multiplied by the solar pump
factor. When the solar pump starts, it runs for a configurable time at
maximum speed before it is then adjusted to run between the mi-
nimum and maximum pump speed.
D
ISTRICT HEATING OPERATION
Operation with district heating is very similar to heating hot water. A
measurement of the temperature difference between the heat
source and the district heating transfer station is used to activate the
district heating pump. If operated without an accumulator, the boiler
supply temperature is used as a reference. If operated with an accu-
mulator, the
Acc. top
temperature is used. District heating opera-
tion must be enabled via a parameter.
The district heating pump must be enabled via the
District
heating available
parameter, or, depending on the hydraulic
system set, may already be active.
The district heating pump is started when the temperature in the
transfer station falls below the
Set temp. dist. heat.
transfer
by the amount of the district heating hysteresis. Priority
for district heating can be set via the parameter
dist. heat.
priority
. For the other mixing circuits, this means that the supply
temperature can be lowered to the reduced temperature for district
heating priority.
C
ONTROL OF SECOND BOILER
The oil-fired boiler is activated when the temperature falls below the
maximum enable temperature for the heating circuits or hot water
tank for longer than the oil-fired boiler enable time.
If the temperature falls below the enable temperature for heating
hot water, the oil-fired boiler will start. In this mode of operation the
preset oil-fired boiler temperature is the
Max. oil-fired
boiler temperature
. The oil-fired boiler will stop once it has
reached the necessary
DHW Set temperature
or
Max oil
burner temp
.