Central Heating/Central Cooling; Heating Circuit; Heating Circuit And Heat Distribution - Viessmann VITOCAL 300-G Technical Manual

Design information
B
A
K
3
A Overflow
B Supply
C Dirt trap (on-site)
D Low-end controller and valve (on-site)
E Primary pump

3.8 Central heating/central cooling

Heating circuit

Minimum flow rate
Heat pumps require a minimum heating water flow rate (see specifi-
cation), which must be maintained. To ensure the minimum flow rate,
install an overflow valve or low loss header in systems without a heat-
ing water buffer cylinder.
Low loss header
When using a low loss header, ensure that the flow rate on the heating
circuit side is greater than the flow rate on the secondary side of the
heat pump.
To prevent a fault shutdown, the minimum flow rate
of the low loss header must be 3 litres per kW rated heating output.
The heat pump control unit treats a low loss header like a small heating
water buffer cylinder. Therefore, configure the low loss header by
means of the control unit settings as a heating water buffer cylinder.
Note
An additional circulation pump is then required.

Heating circuit and heat distribution

Different heating water flow temperatures are required depending on
the heating system design.
The heat pump reaches a maximum flow temperature of 60 °C.
When using radiators or when modernising or replacing boilers, the
heat pump can be used, subject to the max. flow temperature of
60 °C being observed.
VIESMANN
46
(cont.)
D
C
VL
RL
E
H
RL
G
F
F To the heat pump
G Primary circuit heat exchanger (see page 45)
H Circulation pump (≙ well pump)
K Water container
(min. 3000 litre capacity, on-site)
Systems with large water volumes
Systems with large water volumes (for example, underfloor heating
systems) can operate without a heating water buffer cylinder. In these
heating systems, install an overflow valve at the heating circuit distrib-
utor of the underfloor heating system that is furthest away from the
heat pump. This safeguards the minimum flow rate, even in sealed
heating circuits.
In conjunction with an underfloor heating system, install a temperature
limiter as maximum temperature limiter (accessory, order no.
7151 728 or 7151 729).
Systems without heating water buffer cylinder
To safeguard the minimum heating water flow rate (see specification),
never install a mixer in the heating circuit.
The lower the selected maximum heating water flow temperature, the
higher the seasonal performance factor of the heat pump.
VITOCAL 300-G