Viessmann Vitocal 222-G User Manual page 110

Vitocal 300-G/350-G
4.9 Vitocal 300-G/350-G, two-stage, one heating circuit without mixer, one heating circuit
with mixer, DHW heating, heating water buffer cylinder and external heat source (dual
mode parallel operation)
ID: 4605357_1304_04
Application range
Apartment building and buildings for commercial use with two different
heating circuits. Size DHW cylinder eP in accordance with current
standards and requirements.
Main components
■ Vitocal 300/350-G, type BW or BWS
■ Vitotronic 200, type WO1B
■ Heating circuit distributor with one heating circuit without mixer and
one heating circuit with mixer
■ DHW cylinder
■ Heating water buffer cylinder
■ External heat source
Heating water buffer cylinder
The minimum flow rate of heat pump stages 1/9 is safeguarded via
heating water buffer cylinder zP and secondary pumps 6/qP. It is
possible to use differential pressure-dependent heating circuit pumps
uZ and oZ.
Central heating by heat pump
Heat pump 1 and secondary pump 6 start when the actual tem-
perature captured by buffer temperature sensor zQ falls below the set
temperature selected at control unit 2.
If the output from stage 1 is insufficient, stage 2 9 as well as primary
pump wT and secondary pump qP are also started to raise the heating
output.
Control unit 2 regulates the flow temperature in the secondary circuit
and thereby the heating circuit. Secondary pumps 6/qP deliver the
heating water to heating water buffer cylinder zP. Heat pump stages
1/9 with primary pumps 5/wT and secondary pumps 6/qP stop
when the set return temperature is reached. Heating circuit pumps
uZ and oZ deliver the required water volume to the heating circuits.
The heating circuit flow rate is regulated by opening and closing the
thermostatic radiator valves or the underfloor distributor valves and/or
through an external heating circuit control unit.
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.
System examples
(cont.)
To balance the difference in water volume between the primary and
secondary circuits, operate heating water buffer cylinder zP in parallel
to the heating circuits. Any heat not absorbed by the heating circuits
is stored in heating water buffer cylinder zP. In addition, heat pump
stages 1/9 achieve longer runtimes.
Both stages 1/9 of the heat pump will restart when the temperature
at temperature sensor zQ in 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 by heat pump
In the delivered condition, DHW heating by heat pump stage 1 is
given priority over the heating circuit and takes precedence at night.
The heat demand is issued via upper cylinder temperature sensor
eW and control unit 2, which controls the circulation pump for cylinder
heating 7, cylinder loading pump eE and motorised 2-way valve eZ.
Control unit 2 raises the flow temperature to the value required for
DHW heating.
The cylinder temperature can be raised above 60 °C with external heat
source tP.
Central heating with an external heat source
If the heat pumps are unable to maintain the required flow temperature
(captured by flow temperature sensor zW), external heat source tP is
requested. 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. Mixer tR closes towards the
heating circuit when the required flow temperature has been achieved.
External heat source tP is shut down when the flow temperature (cap-
tured by zW), with mixer tR closed towards the heating circuit, no lon-
ger falls below an adjustable threshold for a given period (i.e. there is
either no longer any heat demand or heat pump 1/9 is supplying
adequate heat).
4
VIESMANN
115