Viessmann VITOCAL 300, Installation And Service Instructions Manual

Page: 11 / 160

Heating circuit
Heat pumps require a minimum heat-
ing water flow rate. Ensure that the
values specified in the relevant data-
sheet are maintained.
The minimum flow rate may be safe-
guarded through a heating water buf-
fer cylinder or an overflow valve in
that heating circuit which is the furth-
est removed from the heat pump.
This safeguards a minimum volume of
circulating water, even when the ther-
mostatic valves are closed. Equip
underfloor heating circuits with a tem-
perature limiter (accessories).
Pump protection
To protect the circulation pumps
against seizing up during longer idle
periods (standby mode during holi-
days, heating circuit pumps in sum-
mer), all pumps directly controlled by
the heat pump control unit are started
for 10 s every day at 13:00 h.
Low loss header
When using a low loss header, ensure
that the flow rate at the heating circuit
side is greater than the flow rate at the
secondary side of the heat pump.
The heat pump control unit treats a
low loss header like a small buffer
cylinder. The low loss header must therefore
be configured as a buffer cylinder in
the control unit settings (see
page 115).
Systems without heating water buffer cylinder
Never install a mixer to safeguard the
minimum heating water circulation
volume.
Function description for the individual system versions
11
Preparing for installation
55
92
901
GB