Viessmann VITOCAL 200-G, Installation And Service Instructions Manual

Page: 12 / 208

Heating circuit
Heat pumps require a minimum heat-
ing water throughput. Ensure that the
values specified in the relevant data-
sheet
are maintained .
Accurately calculated radiator heating
systems generally have a small sys-
tem water content. With systems like
these, use a heating water buffer
cylinder with an appropriate capacity
to prevent the heat pump from being
switched on and off at frequent inter-
vals.
Heat pumps can be shut off by the
power supply utility at peak load times
depending on the power tariff. For this
reason a heating water buffer cylinder
should be installed for rapidly cooling
heating systems (radiators). The
volume of the heating water buffer
cylinder should be sufficient to pre-
vent the stored heat from allowing the
building to cool down during power-
OFF periods.
System versions 2 to 4 do not use a
secondary pump but a separate circu-
lation pump as heating circuit pump.
We recommend the use of a heating
circuit pump with a slower throughput
than the secondary pump. Install a
heating water buffer cylinder in paral-
lel to the heating circuit to compen-
sate for the difference between these
water volumes.
Systems with large volumes, e.g.
underfloor heating systems, will not
necessarily require a heating water
buffer cylinder. In these heating sys-
tems install an overflow valve at the
underfloor heating system heating cir-
cuit distributor that is furthest away
from the heat pump. This ensures that
the minimum water circulation volume
is provided, even in closed heating
circuits.
Install a temperature limiter (acces-
sory, part no. 7151 728 or 7151 729)
in conjunction with an underfloor heat-
ing system circuit (particularly if an
instantaneous heating water heater is
installed). Install the temperature lim-
iter, for example, on the underfloor
heating circuit pump.
Heating water buffer cylinder operated in parallel
Heating water buffer cylinders provide
a hydraulic separation between the
media circulating in the heat pump
and the heating circuits. For example,
the throughput in the heat pump cir-
cuit remains constant, even if the
heating circuit throughput is reduced
by thermostatic valves. The use of a heating water buffer
cylinder offers the following advan-
tages:
&
Bridging power-OFF periods
&
Constant throughput through the
heat pump
&
Longer heat pump operating times
Function description of systems
(cont.)
12
Preparing for installation
55
92
968
GB