Viessmann Vitocal 222-G User Manual page 141

Vitocal 200-S/222-S/242-S
5.5 Vitocal 200-S, type AWB-AC, one heating circuit without mixer, one heating circuit with
mixer, DHW heating, heating water buffer cylinder, external heat source and active cooling
via heating circuit M2
ID: 4605170_1304_07
Application range
Detached houses with cooling demand, two heating circuits with dif-
ferent utilisation patterns. Size the DHW cylinder in accordance with
current standards and requirements.
Main components
■ Vitocal 200-S, type AWB-AC, with Vitotronic 200 control unit, type
WO1C
■ Heating circuit distributor with one heating circuit without mixer and
one heating circuit with mixer (KM BUS)
■ DHW cylinder
■ Heating water buffer cylinder
■ External heat source with Vitotronic 200, types KO1B, KO2B or
KW6B
Heating water buffer cylinder
The minimum flow rate of the heat pump is safeguarded via heating
water buffer cylinder zP and secondary pump 6. It is possible to use
differential pressure-dependent heating circuit pumps uZ and oZ.
5
Central heating by heat pump
If the actual temperature captured by buffer temperature sensor zQ of
heating water buffer cylinder zP is lower than the set value selected
at the control unit, the heat pump, consisting of internal unit 1 and
external unit wO, starts. The heat pump supplies the heating circuits
uP/oP with heat via buffer cylinder zP.
Control unit 2 of heat pump 1/wO regulates the heating water flow
temperature subject to the outside temperature.
Secondary pump 6 in the internal unit delivers the heating water via
3-way diverter valve 5 either to heating water buffer cylinder zP or
to DHW cylinder eP. Heating circuit pumps uZ and oZ deliver the
required water volume to the heating circuits. Any heat not absorbed
by the heating circuits is stored in heating water buffer cylinder zP.
Through the matched output of the inverter controlled compressor,
long runtimes of the heat pump are achieved.
Once the actual flow temperature value at the flow temperature sensor
inside internal unit 1 exceeds the set temperature selected at the
control unit, the heat pump and secondary pump 6 are switched off.
VIESMANN
146
(cont.)
The heat pump restarts when the temperature at upper temperature
sensor zQ of heating water buffer cylinder zP falls below the set value.
During the power-OFF period, the heating circuits will be supplied with
heat from heating water buffer cylinder zP.
DHW heating
In the delivered condition, DHW heating by heat pump 1/wO is given
priority over the heating circuits and takes precedence at night. The
heat demand is issued via cylinder temperature sensor eQ and control
unit 2, which regulates secondary pump 6 and the internal 3-way
diverter valve. The control unit raises the flow temperature to the value
required for DHW heating. The cylinder temperature can be raised with
the external heat source.
Central heating with an external heat source
A demand signal is issued to external heat source tP if heat pump 1/
wO cannot maintain the required flow temperature (captured by system
flow sensor zW of the external heat source). The external heat source
starts; mixer tR initially remains closed towards the heating circuit.
Mixer tR opens towards the heating circuit only when the required flow
temperature has been reached at boiler water temperature sensor
tE of the external heat source.
The external heat source continues to operate until the set value is
reached at system flow temperature sensor zW and mixer tR is
closed.
Note
The system example is only applicable in conjunction with modulating
boilers without lower temperature limit.
Match the heating curve of the external heat source to the heating
curve of the heating circuit with the highest flow temperature. Depend-
ing on the system scope and layout, we recommend that these are
offset upwards in parallel.
Active cooling function
The active cooling function is enabled by control unit 2 if the value
for the cooling limit temperature that can be adjusted at control unit
2 is exceeded at outside temperature sensor 3. Heat pump 1/
wO and secondary pump 6 start. The 3-way diverter valves "Heating/
cooling" iI and iO are switched to cooling. Reversing the refrigerant
circuit cools the water that is transported into cooling circuit uP.
The set flow temperature is controlled via flow temperature sensor
uE and control unit 2. Contact humidistat iE ensures that no con-
densation and therefore damage can occur as a result of low temper-
atures.
Note
All lines where the cold water temperature can fall below the dew point
should be insulated so that they are vapour diffusion-proof.
In cooling mode, safeguard the minimum flow rate in the secondary
circuit. Open valves on the heating circuit distributor fully and perma-
nently or install an overflow valve.
System examples