103
Aquarea air / water heat pump – design handbook 07 / 2014
Project Design
Hydraulics
Heating water quality | Use of buffer tanks
Note
The calculation of the expansion vessel is done according to EN 12828
Heating systems in buildings – Design for water-based heating systems.
For dimensioning with local requirements, design programs from manu-
facturers for expansion vessels can be used generally. These calculate
also the required admission pressure values to be set on the expansion
vessel .
Attention
Aquarea heat pumps may only be installed as closed systems without
direct contact of the heating water to the ambient air. The oxygen trans-
fer in open systems can lead to excessive corrosion of the piping and
thus to problems in operation.
5.13.7 Heating
water quality
5.13.8 Use of buffer tanks
To avoid damage to the heating system and to the heat pump, limestone
formation in drinking water heaters and hot water heating systems must
be observed. Furthermore, heating systems must be flushed thoroughly
prior to filling them.
Buffer tanks can fulfil three functions in connection with heat pumps:
• Bridging outage time by electrical supply companies,
• hydraulic decoupling of the heat pump circuits from the heat transfer
system and
• extension of the heat pump service life by preventing frequent switch
on and off (cycling), which reduces the system efficiency.
Owing to the inverter technology of Aquarea heat pumps, the system
capacity can be regulated in line with the heat requirement, ensuring
efficiency and meaning a buffer tank is not needed, thus saving space.
To bridge the outage time by the electrical supply company, heat transfer
systems with greater storage capacity like underfloor heating systems
can cater for adequate intermediate storage.
3. The final pressure of the pressure relief valve is derived from the
opening pressure of the pressure relief valve minus a tolerance
of 0.5 bar:
p
e
= opening pressure pressure relief valve minus 0.5 bar
4. The admission pressure p
0
must be such that it corresponds to the
static head of the heating system and an additional pressure of max.
0.5 bar. A static head of 10 metres corresponds to 1 bar. The admission
pressure of the Aquarea expansion vessel may have to be adjusted.
