Viessmann VITOCAL 242-G Installation And Service Instructions Manual page 15

Function description of systems
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.
The use of a heating water buffer
cylinder offers the following advan-
tages:
Systems without heating water buffer cylinder
Never install a mixer to safeguard the
minimum heating water circulation
volume.
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 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.
Preparing for installation
(cont.)
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 larger)
expansion vessel should be provided.
Protect the heat pump with a fuse in
accordance with DIN 4751 [or local
regulations].
During the cooling operation, the heat
pump will only be started to provide
DHW. The heat pump control system
actuates the circulation pumps, diver-
ter valves and mixers and records the
temperature via the natural cooling
extension kit. Alternatively, this func-
tion can also be covered by on-site
components (for an on-site wiring
suggestion, see the Vitocal 200/222/
242 technical guide).
A contact humidistat monitors the dew
point.
The capability of the natural cooling
function cannot generally be com-
pared with that of air-conditioning
equipment or water chillers. Natural
cooling provides no dehumidification.
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