Heating Circuits/Cooling Circuits - Viessmann VITOTRONIC 200 Service Instructions Manual

Function description

Heating circuits/cooling circuits

Notes on minimum flow rate
Heat pumps require a minimum flow rate in the secon-
dary circuit, which must be maintained.
Note
With brine/water heat pumps a minimum flow rate
must also be maintained on the primary side.
Minimum flow rates
Installation and service instructions of the rele-
vant heat pump
System with small water volumes, e.g. heating sys-
tems with radiators
To avoid excessive compressor cycling (starting/stop-
ping), the heating system volume must be increased.
This can be achieved by using buffer cylinders as fol-
lows:
Buffer cylinder connected in parallel to the heating
■
circuits with a volume matched to the heat pump out-
put.
■ Heating water buffer cylinder connected in series in
the secondary circuit return or pre-cooling vessel
with small volume, e.g. 50 l.
System configurations
The heat pump control unit can switch 1 heating circuit
without mixer (A1/HC1) and up to 2 heating circuits
with mixer (A2/HC2, A3/HC3).
In combination with a heating water/coolant buffer cyl-
inder, it is able to cool 3 heating circuits simultane-
ously.
If just a heating water buffer cylinder is installed in the
heating system, one of the 3 heating circuits can be
used for cooling (as a heating/cooling circuit) or a sep-
arate cooling circuit can be switched ("Cooling circuit
7101").
48
With air/water heat pumps, a higher system volume
ensures that the thermal energy required for defrosting
is always available in the secondary circuit.
Minimum heating system volume
"Technical guides for heat pumps"
Systems with large water volumes, e.g. underfloor
heating systems
Systems with large water volumes can operate without
a buffer cylinder. In these heating systems, install an
overflow valve at the heating circuit distributor of the
underfloor heating system that is furthest away from
the heat pump. This guarantees the minimum flow
rate, even when the thermostatic valves are closed.
Note
A buffer cylinder connected in parallel must always be
used in the case of heating circuits with mixers.
Exception : If the installation kit with mixer (acces-
sories) is installed in a heat pump compact appliance,
the heating circuit with mixer M2/HC2 can be connec-
ted directly ("Type of assembly kit 7044" set to "1").
Note
If a separate cooling circuit is connected, cooling can
not take place via a heating/cooling circuit.