Technical data

www.dimplex.de 01.2012 | Project planning manual for heat pumps for heating and domestic hot water preparation | 51
Water-to-water heat pump 4.3.2
4.3 Tapping the heat source
4.3.1 Direct use of water of consistently good quality
Water with temperatures between 8 °C and 25 °C can be directly
used in water-to-water heat pumps if the compatibility of the
ground or cooling or waste water has been proven according to
Table 4.2 on page 50.
If the water quality is evaluated as being too poor, or if the water
quality varies (i.e. in the case of a fault), a heat pump equipped
with an intermediate circuit (see Chapt. 4.3.2 on page 51) must
be installed.
4.3.1.1 Ground water as a heat source
Extraction well
The ground water which the heat pump uses as its heat source is
extracted from the ground via an extraction well. The well output
must guarantee continuous extraction to ensure the required
minimum water flow rate of the heat pump.
Absorption well
The ground water cooled by the heat pump is returned to the
ground via an absorption well. The absorption well must be
drilled 10 - 15 m downstream from the extraction well in the direc-
tion of the ground water flow in order to ensure that the flow is not
"short-circuited". The absorption well must be able to accommo-
date the same amount of water as the extraction well supplies.
NOTE
Because the operational reliability of the system depends on the design
and construction of the wells, this work should be carried out by an expe-
rienced well constructor.
NOTE
Before commissioning the heat pump, a 48-hour test run must be carried
out on the primary pump to ensure that the minimum volume flow on the
heat source side can be permanently guaranteed. This must be confirmed
for commissioning requests.
NOTE
A list of qualified well constructors is available at www.dimplex.de.
Fig. 4.1: Example for the integration of a water-to-water heat pump with ex-
traction and absorption wells
4.3.1.2 Waste heat from cooling water as the heat source
Temperature range
For utilising water with temperatures between 8 and 25 °C, it
must first be clarified whether the cooling water is available in
suitable quality and quantity, and to what extent the heat gener-
ated by the heat pump can be used.
If the compatibility of the cooling and waste water is permanently
ensured according to Table 4.2 on page 50, a water-to-water
heat pump can be used.
ATTENTION!
If the heat source temperature can rise to over 25 °C, the temperature-
controlled mixer is required that, for temperatures over 25 °C, adds a
partial volume flow of the cooling water outlet to the the cooling water.
4.3.2 Indirect use of water as a heat source
If the compatibility of the water cannot be proven or if there is any
danger that the water quality may change, an intermediate heat
exchanger must be installed upstream to protect the heat pump.
The intermediate circuit increases the operational safety, in par-
ticular if a brine-to-water heat pump is used and the secondary
circuit is thus filled with brine. (Chapt. 3.5 on page 45)
A water-to-water heat pump with intermediate heat exchanger
should only be used when the use of brine as a heat transfer me-
dium is not permitted and permanent water temperatures of
above 10 °C (e.g. waste heat from production processes) can be
guaranteed.
NOTE
Generally, brine-to-water heat pumps should be installed in order to ex-
pand the range of operating temperatures to also include lower tempera-
tures and thus increase operational safety. With water-to-water heat
pumps, the lower operating limit is already reached at an outlet tempera-
ture of 4 °C.
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