Technical data
46 | Project planning manual for heat pumps for heating and domestic hot water preparation | 01.2012 www.dimplex.de
3.5.2 Brine-to-water heat pump
3.5.2 Expanding the operating temperature range
If the heat source temperatures fluctuate, it is advisable to use a
brine-to-water heat pump, as they permit minimum brine outlet
temperatures of -9 °C. By comparison, water-to-water heat
pumps switch off from a minimum water outlet temperature of 4
°C. The maximum brine inlet temperature for both brine-to-water
and water-to-water heat pumps is 25 °C. Various different meas-
ures can be used to ensure that the operating limits are reached
and not exceeded.
NOTE
The efficiency of the heat pump is reduced if the brine inlet temperature
falls.
Fig. 3.15: Heat pump with three-way valve in the brine circuit
Version 1 - heat pump with three-way valve
A thermostat-controlled three-way valve is installed in the brine
circuit. If the brine inlet temperature rises above 25 °C, a partial
volume flow of the brine return is added to the brine flow via the
mixer. The mixer is controlled via an external controller.
Version 2 - heat pump with buffer tank in the brine
circuit
Version 2 uses a buffer tank in the brine circuit (see Fig. 3.16 on
page 46). The buffer tank is charged with pump P1 via an exter-
nal control. When a minimum temperature of 3 °C is reached in
the buffer tank, the pump is activated and charged. From a max-
imum temperature of 24 °C, the pump P1 switches off. The heat
pump manager activates the heat source pump (primary circula-
tion pump M11) in the brine circuit. If the temperature sensor
(R6) registers a temperature below 3 °C or a temperature of 25
°C, the heat pump manager switches the heat source pump off.
The brine circuit must be filled with glycol with a concentration of
at least 25%.
NOTE
Low brine temperatures in the buffer tank and the pipework can result in
condensate failure on the buffer tank. The buffer tank must therefore be
fitted with diffusion-proof insulation on-site.
Fig. 3.16: Heat pump with buffer tank in the brine circuit
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