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Planning
5.3
Hydraulics
5.3.1 Hydraulic integration
All Aquarea heat pump systems have an integrated water circulation pump that provides trans-
port of the heating water into the heat transfer system. A high-efficiency pump is used for the
purpose.
In general, a hydraulic disconnection of heat pump circuit and heat consumer circuit is always
advisable if other volumetric flows must be provided than is required for the heat pump circuit.
In such a case, separate pumps must be provided for the respective circuits. To avoid these
pumps influencing each other with their different pressure and volumetric flow parameters, hy-
draulic disconnection is necessary.
If, besides the integrated water circulation pump, one or more water circulation pumps are re-
quired for the respective heating circuits, hydraulic disconnection of the heat pump circuit and of
the heat consumer circuit through a buffer tank or a hydraulic shunt must be effected.
For integrating without hydraulic disconnection, it must be ensured that the minimum flow rate of
the respective heat pump
(→ 4 Technical data (split systems), p.
(compact systems), p.
50) is maintained at all times. Automatically regulating mixer or ther-
mostat valves can ensure that the hot water circulation is throttled so strictly that the flow rate
falls below the minimum. To rule this out, Panasonic recommends always installing heat transfer
systems without hydraulic disconnection with an overflow valve between heating flow and re-
turn. The overflow valve is to be designed for the nominal flow rate of the respective heat pump.
Another option is a bypass in the form of multiple non-adjustable or permanently opened heat-
ing circuits. Rooms with a continuously high heat requirement, such as bathrooms, are partic-
ularly suited for this purpose. Even for this variant, it is necessary to ensure that the minimum
flow rate of the heat pump is always guaranteed.
Magnetic filter
Panasonic recommends installing a magnetic filter that is to be installed for protection of the
heat pump on site before the connection of the water inlet (water return) on the heat pump.
System volume
Depending on the nominal heating capacity of the heat pump system, the recommendations for
the minimum total water volume in the system are as follows:
Nominal heating capacity up to and including 9 kW: 30 litres
Nominal heating capacity above 12 kW up to and including 16 kW: 50 litres
!
IMPORTANT
If the total water volume in the system is below the indicated values, the system volume should
be increased, say, by using a buffer or an additional vessel.
100
Aquarea air-to-water heat pumps - Planning and installation manual - 01/2018
16,
→ 4.6.3.3 Technical data
5.3.2 Discharge head
Discharge head and displacement volume of the integrated water circulation pumps depend on
the respective heat pump model (see technical data of the respective pump).
Pipe network resistance
Designing the pump discharge head requires consideration of all components of the pipe net-
work and their individual resistances for nominal flow rate. Choose components such as mixer,
valves and counters for the amount of heat such that the nominal throughput is matched to the
nominal flow rate of the heat pump system.
Respecting the Nominal Flow Rate
Heat pumps work for efficient heat generation with a dispersion between inflow and return of
about 5 K. This distinguishes them from heat sources with burners, which can work without any
problem with a dispersion between inflow and return of about 10 or 20 K. The effect of the low
temperature dispersion of heat pumps is that the flow rate of heat pumps for the transport of the
same thermal output must tend to be higher than for heat sources with burners. The nominal
flow rate and the resulting resistance of the pipe network must therefore be given special atten-
tion at the time of planning.
Respecting the Nominal Tube Width
The pressure gradient in the pipeline rises exponentially with the flow rate. This means that
doubling the flow rate causes the pressure gradient to increase by a factor of 4. Decisive for it is
the flow speed in the tube that depends on the flow rate and inner diameter.
As an alternative to a tube network calculation, the pressure gradient can be determined in tube
sections through nomograms. Recommendations for designing the main distribution circuit are:
● The flow speed should be in the range of 0.3 to max. 1.5 m/s.
● The pressure gradient per metre should be about 0.1 kPa/m.
Based on these criteria, the required nominal tube width can be read off from the copper tube
nomogram. To determine the pipe network resistance of a whole line section, the pressure
gradient per metre must be multiplied by the length of the respective section and the pressure
gradient of the sections added. The total resistance of a section is obtained as the total of the
pressure gradient of the sections multiplied by a lump sum supplement factor of 1.5.
!
IMPORTANT
The total of the individual resistances of all components of the pipe network must not exceed
the pump discharge head for nominal flow rate. If the pipe network resistance is too high, the
device's internal water circulation pump cannot achieve the nominal flow rate. The heat pump
regulation registers a shortfall of the minimum circulation quantity and switches to Fault.
5.3.3 Hydraulic Balancing
The hydraulic balancing of the heat transfer system is the correct setting of the set flow rate of
sections through regulating valves. This prevents individual building areas being excessively
overheated, while other areas remain cold with lower flow. The hydraulic balancing therefore
raises the living comfort and is, at the same time, also a requirement for efficient operation of
the air-to-water heat pump. A hydraulic balancing must therefore also to be performed for the
financial promotion of heat pumps.
Aquarea air-to-water heat pumps - Planning and installation manual - 01/2018
Planning
101
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