Function Description In Connection With The System Versions - Viessmann Vitocal 300-G Installation And Service Instructions Manual

Preparing for installation

Function description in connection with the system versions

Note
The sample applications are recommendations and must be checked for com-
pleteness and functionality on site. Please observe the applicable regulations
and directives for design, installation and operation.
Heating circuit
Heat pumps require a minimum
throughput of heating water (see
specification on page 208). Ensure
that the values specified in the rele-
vant datasheet 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 peri-
ods depending on the power tariff. For
this reason install a heating water buf-
fer cylinder in rapidly cooling build-
ings.
Heating water buffer cylinder operated in parallel
Heating water buffer cylinders provide
a hydraulic separation of the flow in
the heat pump and heating circuits.
For example, the flow rate in the heat
pump circuit remains constant, even if
the heating circuit flow rate is reduced
by thermostatic valves.
Use of the heating water buffer cylin-
der:
14
The system versions with heating
water buffer cylinder do not use a sec-
ondary pump but a separate circula-
tion pump as heating circuit pump. We
recommend the use of a heating cir-
cuit pump with a slower flow rate than
the secondary pump.
Systems with large water volumes, e.
g. underfloor heating systems, can
operate without a heating water buffer
cylinder. In these heating systems
install an overflow valve at the under-
floor heating system heating circuit
distributor that is furthest away from
the heat pump. This ensures that the
minimum circulation volume is pro-
vided, even in closed heating circuits.
In conjunction with an underfloor
heating system, install a temperature
limiter (accessory, order no. 7151 728
or 7151 729) (connection, see
page 78).
Bridging power-OFF periods
Constant flow rate through the heat
pump
Longer heat pump operating times
Because of the increased water
volume of the heat source and the fact
that it may have a separate shut-off
facility, an additional (or bigger)
expansion vessel should be provided.