The collector pipe usually consists of a special airtight plastic pipe with a diameter of 150 – 200 mm and is usually laid at a depth of 1.2 to 2 m below the ground surface (frost-proof installation). Depending on the desired heat yield, the pipe length is approx. 20 to max. 40 m, although it is also possible to lay several pipes in parallel to divide the pipe length; however, the pipes should be about 1 m apart from each other so that they do not short-circuit each other.
In this system, the air that is later blown into the room is also the heat-transmitting medium, so special attention must be paid to hygiene inside the pipe. Therefore, the pipes are laid on a slope so that the low point is at the connection point into the house and condensate can be discharged in the building if necessary. In addition, a smooth-walled pipe, protected from dirt ingress by filters, must be used, which does not allow soil air to pass through and in whose connectors no "condensate puddles" can form. During installation, care must be taken to ensure that the pipe is not damaged or slips when the soil is compacted, otherwise the slope may no longer be guaranteed and puddles will inevitably form. In areas with increased radon levels , the use of ground-to-air heat exchangers is not recommended, as otherwise the radon concentration inside the building can rise sharply in the event of leaks at the collector pipe; the use of a brine-guided heat exchanger system is recommended here.
Source: bauwion
