A two-string pipe system, where each radiator on the same floor has the same total distribution pipe length (supply + return – measured from the pump through the radiator and back to the pump) is called a Tichelmann system. It is also commonly referred to as a reverse return system.
Radiators with a short length of supply pipe measured from the pump have a correspondingly longer return pipe. The opposite applies to a radiator located furthest away. This ensures uniform resistance and hence more or less equal water flow-rate in the heating surfaces. Consequently, the water flow for each heating source does not need to be individually adjusted during commissioning. However, this generally leads to longer and more complicated pipe runs and therefore higher system costs.
The system can be used both in heating and air-conditioning systems. The reverse return system is named after Albert Tichelmann, an engineer within the field of hot water heating. Grundfos circulator pumps and in-line single-stage pumps are typically used in a Tichelmann system.