Installation manual

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Brine-to-Water Heat Pump 3.3.3
3.3.2 Preparation of boreholes
The clearance between the heat exchangers should be at least
6 m so that reciprocal interference is kept to a minimum and
regeneration is guaranteed in the summer. If several heat
exchangers are required, these should not be laid out parallel to
the direction of ground water flow, but transverse to it. (see Fig.
3.7 on p. 79).
Fig. 3.7: Layout and minimum clearances between borehole heat
exchangers in relation to the direction of the ground water current
NOTE
The same rules as for ground heat collector systems apply to brine
concentration, materials, layout of the manifold shaft and installation of
the pump and expansion vessel.
Fig. 3.8 on p. 79 shows a cross section through a double U pipe
of the type normally used for heat pumps.
For this type of heat exchanger pipe, a bore hole must first be
drilled with a radius of r
1
. Four heat exchanger pipes and a back-
fill pipe are inserted, and the hole is then back-filled with a
cement/bentonite mixture. The heat exchanger fluid flows
downwards in two of the pipes and flows upwards again in the
other two. The pipes are connected at the lower end with a
borehole head, creating a closed-loop heat exchanger circuit.
Fig. 3.8: Cross section of a double U pipe with back-fill pipe
NOTE
When using brine equipment or heat pumps with an integrated brine
circulating pump, the pressure drops of the borehole heat exchanger
must be determined and compared with the free compression of the brine
circulating pump. To avoid unnecessarily high pressure drops, DN40
pipes should be used for borehole heat exchanger depths of more than
80 m.
3.3.3 Additional heat source systems for ground heat usage
As an alternative to ground collectors, other types of heat source
systems such as ground heat baskets, trench collectors, energy
posts, coil collectors, etc. are also possible.
Dimensioning of these heat source systems must proceed
according to manufacturer or supplier specifications. The
manufacturer must guarantee the long-term functioning of the
system based on the following information:
 Minimum permissible brine temperature
 Cooling capacity and brine flow rate of the installed heat
pump
 Annual operating hours of the heat pump
Additionally, the following information should be made available:
 Pressure drop with specified brine flow rate for dimensioning
the brine circulating pump
 Possible impact on the vegetation
 Installation requirements
Experience shows that the abstraction capacities of classic
ground heat collectors only differ slightly from other systems, as
the energy stored 1m
3
in the ground is limited at 50 to 70 kWh/a.
Possible optimisation of the abstraction capacities depend first
and foremost on the climate conditions and the ground type and
not on the type of heat source system.
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