Viessmann VITOCAL 300 Installation And Service Instructions Manual page 12

Preparing for installation
Function description for the individual system . . .
Heating water buffer cylinder
Where a heating water buffer cylinder
is installed, the secondary side flow
rate should be greater than the flow
rate at the heating circuit side. Where
a heating water buffer cylinder is used
with only one flow and return connec-
tion respectively, this is an absolute
must.
Natural cooling function
During the summer months the tem-
perature level of the primary circuit
can be used to cool the building.
The natural cooling function can be
achieved in two ways:
& On a heating circuit also used for
heating (see system version 1 to 3
from page 18)
& With a separate cooling circuit
installed in addition to the heating
circuits (see page 28). In that case,
install a separate room temperature
sensor to regulate the cooling cir-
cuit.
During the cooling operation, the heat
pump will only be started to produce
DHW. The control unit enables the
natural cooling function as soon as
the outside temperature exceeds the
cooling temperature limit, which can
be adjusted at the control unit. The
primary pump starts and the cooling
circuit pump, the three-way diverter
valve "heating/cooling" and the solar
circuit shut-off valve are controlled via
the natural cooling extension kit.
12
(cont.)
Furthermore, the natural cooling
extension kit processes the signals
from a contact humidistat and a frost
stat.
The cooling circuit mixer will be regu-
lated by the control unit.
The brine/water heat exchanger
installed for system separation trans-
fers the low brine temperatures to the
heating or cooling circuit.
The capability of the natural cooling
function cannot generally be com-
pared with air-conditioning equipment
or water chillers.
The cooling capacity depends on the
heat source temperature, which itself
is subject to seasonal fluctuations.
Radiator heating systems are not sui-
table for cooling buildings. With
underfloor heating circuits ensure that
any installed room thermostats are
opened manually or by servomotors
when the cooling function is utilised.