Brine system planning

With this type of heating system the heat source system consists of a horizontal ground collector or earth probe designed as a closed circuit. The heat transfer medium - brine (water with antifreeze) - is transported through the collector or probe system with a brine pump (energy extraction) and fed to the heat pump (energy transfer).

Plastic pipes with an adequate wall thickness to prevent damage from mechanical influences are used. Installation of the system may have to be registered.

The area of ground to be used for installation of horizontal collectors or earth probes must be undisturbed and not banked up on one side. Otherwise any settlement of the ground could damage the pipes. The higher the moisture content of the soil, the higher and better the heat conduction. So in damp, earthy soil a smaller area of ground will be needed for heat extraction than in dry, stony soil.

The area of ground chosen for heat extraction must be undeveloped but may be planted. Rainwater is important for regenerating the soil. Backwater and flooding (e.g. on sloping sites or clayey soils) must be avoided because of the risk of ground instability and structural damage. Drainage must be provided if necessary. Allow the ground to settle before starting heat extraction.

The area of ground required depends on the cooling capacity of the heat pump in heating mode (model, intended coefficient of performance) and the specific heat extraction capacity of the soil.
The laying depth is normally around 1.2 to 1.4 m, but may be lower in some regions. The spacing between the pipe loops must be calculated. For standard collector tubes the current guide value is 40 to 60 cm.

The pipes are generally laid on level, horizontal subsoil or with at most one lateral slope (sloping site). On sloping sites the ground collector tubes must always be laid perpendicular to the slope. The installation must be well ventilated.

Make sure that the pipes are not kinked or compressed. Before covering with soil, protect the ground collector tubes with a bed of sand. Warning tape should be laid about 50 cm above the collector tubes.

The probe depth may be up to 100 m, depending on the system (deeper boreholes are possible). The distance between the probes should be at least 6 m.

A geological survey must be carried out before work is started. This will provide information about possible rock strata, the likely subsoil and the exact extraction output. Probe drilling must be carried out professionally by a licensed company. If the geological conditions are unclear, a test bore should be drilled. The probe must also be installed by the drilling company. The probe must be washed in correctly and aquifers must be sealed off if necessary. In non-consolidated soils the borehole has to be braced!

With large-scale collector systems or if the heat pump is more than 10 m away from the collector system, a collecting chamber must be provided. This can be built conveniently using commercial concrete rings. The connecting lines from the building to the collecting chamber must be laid straight and with a slight incline towards the collecting chamber. This allows any condensation to drain away. The connection must be thermally insulated or a penetration sleeve used.

A minimum clearance of 1.5 m from water supply mains is required. A minimum clearance of 1 m from drains is required. If pipes are laid parallel to buildings, a safety clearance of around 1.2 m should be allowed. (Prevent frost damage.)

If these safety clearances cannot be complied with, special measures must be taken: insulate the structure to be protected and/or the collector tubes with a closed-pore insulating material.