The present invention relates to a ground circuit in a low-energy system, said ground circuit comprising a connection pipeline (3), collection pipe system (2) and a return pipeline (4) for circulating a transfer fluid. The ground circuit is utilized for transferring thermal energy recovered from its surroundings, for instance, to a heat pump (5) or the like. The present ground circuit collection pipe system (2) is characterized by consisting of a hollow profile (6) arranged to be a coil, whereby the hollow profile is connected at its first end to a connection pipeline (3) for conveying the transfer fluid along the hollow profile from the first coil end to the second, and at the second end of the coil the second end of the hollow profile is connected to the return pipeline (4) for conveying the transfer fluid from the hollow profile towards the place where used. At the opposite ends of this hollow profile there are advantageously arranged means for controlling the fluid flow provided therein.