Internal versus External

Pressure drop between the valve outlet and the evaporator outlet is the most important of the low-side pressure losses that affect valve performance. These pressure drops will hold a TEV in a relatively “restricted” position. This will reduce system capacity unless a valve with an external equalizer is used.

These figures show the internal differences between the internal and external equalized valves. In the externally equalized valve, there is packing(blue line) around the push rods that keep outlet pressure away from the diaphragm. Instead, suction pressure is applied to the evaporator side of the diaphragm through tubing.

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