Distributor

A distributor splits the liquid refrigerant leaving the expansion valve into a number of parallel circuits in the evaporator, so that each circuit receives the same share of the flow. Without one, a multi-circuit coil would feed unevenly: the circuits nearest the inlet would flood and the far ones would starve, and the evaporator would perform well below its rating even though the valve was correctly sized.

The part number describes the geometry directly. N is the number of outlet holes, A is the diameter of each distributing hole, and B is the inlet connector size - so a 12-4.0-16 has twelve outlets with 4.0 mm holes and a 16 mm inlet.

Holes run from 2 to 48, outlet distributing holes are produced in 4.0, 4.76, 5.0, 6.35 and 7.94 mm, and inlet connectors from 6.35 mm to 42 mm. The body is machined from C3771 forged brass, which is the grade normally specified for this part because it machines cleanly and holds a precise hole size - the accuracy of those holes is what determines whether the distribution is even.

Selection is by circuit count and by capacity per circuit: the nozzle has to pass the design flow at the pressure difference available, and it must be matched to the expansion valve capacity. A distributor with the wrong nozzle size is one of the most common causes of a coil that ices unevenly.

Installation: keep the distributor horizontal and the capillary tubes equal in length where possible; where lengths must differ, keep the difference small and route them symmetrically. Unequal or badly routed capillaries produce uneven circuit loading no matter how well the nozzle is sized.