Two-Pipe, Reverse-Return System
A two-pipe, reverse-return system (Figure 7-7) achieves a balance in the water supply by creating circuits to the radiators of approximately equal length. Instead of allowing the return supply of water to proceed directly to the boiler from each radiator, the return main carries the water in the opposite direction for a predetermined distance before turning back to the boiler. The first radiator has the shortest supply main but the longest return main. For the farthest radiator, the reverse is true. Regardless of the position of a radiator in the system, the total length of pipe within the circuit of which it forms a part will be essentially the same as that of any other circuit.
Posted in Audel HVAC Fundamentals Volume 1 Heating Systems, Furnaces, and Boilers