Cooling Operation; Systems With Heating Water Buffer Cylinder; Heating Water Buffer Cylinder Operated In Parallel - Viessmann VITOCAL 300-G Technical Manual

Design information
90
80
E
70
65
60
50
40
30
20
10
+18 +14 +10
Outside temperat. t A in °C
A Max. heating water flow temperature = 75 °C
B Max. heating water flow temperature = 60 °C
C Max. heating water flow temperature = 55 ºC, requirement for
mono-mode operation of the heat pump
D Max. heating water flow temperature = 35 ºC, ideal for mono-
mode operation of the heat pump

Cooling operation

Cooling mode is possible either with one of the available heating cir-
cuits, or with a separate cooling circuit (e.g. chilled ceilings or fan con-
vectors).
Operating modes
Cooling operation via the heating circuits is carried out in the "Stand-
ard" and "Fixed value" operating modes. The separate cooling circuit
is additionally cooled in "Reduced" and "DHW only" operating modes.
The latter enables continuous cooling of a room, e.g. a warehouse
during the summer months.
The cooling output is subject to either weather-compensated control
according to the heating or cooling curve, or room temperature-
dependent control.
Note
For cooling mode in the following cases, a room temperature sensor
must be installed and enabled:
■ Weather-compensated cooling mode with room influence
■ Room temperature-dependent cooling mode
■ "Active cooling"
A room temperature sensor must always be installed for a separate
cooling circuit.

3.9 Systems with heating water buffer cylinder

Heating water buffer cylinder operated in parallel

Systems with small water volumes
For systems with small water volumes (for example, heating systems
with radiators), use a heating water buffer cylinder to prevent exces-
sive heat pump cycling (starting/stopping).
VITOCAL 300-G
(cont.)
+2 0 -2 -10
A
B
C F
D
-14
E Heating systems that are conditionally suitable for dual mode
operation of the heat pump
F Max. heat pump flow temperature = 60 ºC
Weather-compensated control
In weather-compensated cooling mode, the set flow temperature is
calculated from the relevant set room temperature and the current
outside temperature (long-term average) according to the cooling
curve. Their level and slope are adjustable.
Standard operation
The cooling output for the heating circuits is subject to either weather-
compensated control according to the cooling curve, or room temper-
ature-dependent control.
Fixed value operation
In "Fixed value" mode, the room is cooled with the minimum flow tem-
perature.
Benefits of a heating water buffer cylinder:
■ Bridging power-OFF periods:
At peak times, heat pumps may be switched off by your local power
supply utility, subject to your electricity tariff. A heating water buffer
cylinder supplies the heating circuits even during this power-OFF
period.
■ Constant flow rate through the heat pump:
Heating water buffer cylinders provide hydraulic separation of the
flow in the secondary and heating circuits. For example, the flow rate
in the secondary circuit remains constant even if the heating circuit
flow rate is reduced via thermostatic valves.
■ Longer heat pump operating times
3
VIESMANN
47