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Aquarea air / water heat pump – design handbook 07 / 2014
Project Design
Heat pump selection
Performance curves
Performance curves of the Aquarea-LT series for the Bi-Bloc systems with design point,
heating limit temperature and bivalent point
This illustration shows the characteristic curve for the split systems of
the Aquarea LT series with different flow temperatures giving different
heating capacities at a given outdoor temperature. By plotting the design
point (Heating capacity = 12 kW @ Ɵe = -2.0 °C) and the point at which
there is no heating demand (Ambient external air temperature, in this
example 20 °C) and then connect the two points. Where this line crosses
the HP performance curve, this is the bivalent point.
For monovalent operation of the heat pump, the selected heat pump
must provide a larger capacity than the design heating capacity. In the
above example only the 16 kW heat pump at 35 °C flow temperature
provides more capacity than required. (12.2 kW > 12 kW)
For reasons of economic viability or practicalities such as an existing
heating system, the heat pump can be sized as a bivalent system. Using
the 12 kW Aquarea-LT heat pump, a bivalence point of 0 °C is found.
Below this outside temperature the heat pump will need support,
whereas above this temperature the heat pump will run unsupported.
In a bivalent alternative scheme, 0 °C is the switch over point.
16 kW (three phase)
14 kW (three phase)
12 kW (three phase)
Supply water
temperature 35 °C
Supply water
temperature 55 °C
-10
-15
-5
0
5
16
14
12
10
8
6
4
2
0
10
15
20
25
Heating capacity [kW]
Outside temperature [°C]
Heating limit
temperature
Design point
12 kW HP Bivalent point
