Bulb should be clamped to the suction line near the evaporator outlet, and if possible, on a horizontal run.
Clean suction line completely before clamping the bulb in place. Clamp the bulb to a free draining suction line. Insulate the remote bulb from ambient. Locate equalizer line as close to bulb as possible on downstream side. Downstream positioning of the equalizer line is recommended.
Why? If the TEV valve stem packing leaks, then liquid refrigerant will travel thru the equalizer line from high to low side, bypassing the bulb. If the equalizer line is upstream of the bulb, and the packing leaks, the refrigerant passing through the equalizer line will keep the sensing bulb artificially cold, thus forcing the TEV to remain in a closed position (i.e. high superheat.) If the above occurs with the equalizer line piped downstream, refrigeration will occur. A small leak will have relatively no effect on superheat. However, a large leak can cause a high superheat at the evaporator, while simultaneously causing a low superheat at the compressor.
NOTE: A leaking valve stem packing is easily diagnosed by a frosted equalizer line, if on low or medium temperature systems. Change the cage or TEV before compressor damage occurs. If more than one TEV is used on adjacent evaporators or evaporator sections, make sure that the remote bulb and equalizer line of each valve is applied to the suction line of the evaporator fed by that valve.