Viessmann Vitocal 300-G Installation And Service Instructions Manual page 15

Function description in connection with the system . . .
Protection of the heat pump in accor-
dance with EN 12828 [or local regula-
tions].
Systems without heating water buffer cylinder
Maintain the minimum heating water
circulation volume (see specification
on page 210):
Natural cooling (NC) function
During the summer months the tem-
perature level of the primary circuit
can be used to cool the building "natu-
rally".
The natural cooling (NC) function is a
method of cooling buildings that
saves a considerable amount of
energy. All that is needed is a small
amount of electricity for the circulation
pumps to access the "cooling source"
in the ground.
During cooling operation, the heat
pump will only be started to produce
DHW. The heat pump control system
regulates the circulation pumps,
changeover valves and mixers and
records the temperature via the nat-
ural cooling extension kit (accessory).
Alternatively, this function can also be
covered by on-site components (for a
suggested on-site connection, see
technical guide).
A contact humidistat monitors the dew
point.
The capacity of the natural cooling
function cannot generally be com-
pared with that of air-conditioning
equipment. Natural cooling provides
no dehumidification.
Preparing for installation
e.g. fit an overflow valve.
Never install mixers.
The refrigerating capacity depends on
the temperature, which is subject to
seasonal fluctuations. Experience has
shown that the cooling capacity is
higher at the beginning of summer
than at the end.
In addition, the water source tempera-
ture curve is subject to the cooling
demand of the building. Large window
areas or internal heat sources
(lighting, electrical equipment)
increase the temperature in the
ground (geothermal probe) more
rapidly during the course of a year
than in building with fewer heat gen-
erators, reducing the effect of natural
cooling.
Underfloor heating systems and con-
crete core tempering are available for
cooling the building; radiator heating
systems are unsuitable for this pur-
pose. Ensure that any installed room
thermostats are able to be opened
manually or by servomotors when
using the cooling function.
(cont.)
15