Viessmann Vitocal 300-G BW, Installation And Service Instructions Manual

Page: 15 / 216

15
Because of the increased water volume
of the heat source and the fact that it may
have a separate shut-off facility, an addi-
tional (or bigger) expansion vessel
should be provided. Protection of the heat pump in accord-
ance with EN 12828 [or local regula-
tions].
Systems without heating water buffer cylinder
Maintain the minimum heating water cir-
culation volume (see specification on
page 205): ■ e.g. fit an overflow valve.
■
Never install mixers.
Natural cooling (NC) function
During the summer months the temper-
ature level of the primary circuit can be
used to cool the building "naturally".
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 natural cooling extension kit
(accessory). Alternatively, this function
can also be covered by on-site compo-
nents (for a suggested on-site connec-
tion, see technical guide).
A contact humidistat monitors the dew
point.
The capacity of the natural cooling func-
tion cannot generally be compared with
that of air-conditioning equipment. Natu-
ral cooling provides no dehumidifica-
tion. The refrigerating capacity depends on
the temperature, which is subject to sea-
sonal 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 tem-
perature in the ground (geothermal
probe) more rapidly during the course of
a year than in building with fewer heat
generators, 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 purpose.
Ensure that any installed room thermo-
stats are able to be opened manually or
by servomotors when using the cooling
function.
Preparing for installation
Function description in connection with the…
(cont.)
5368 522 UAE
Installation