I've run across a good size (450k BTU/h) chiller and am puzzled by the placement of the bulbs for the expansion valves (Alco THR).

On a similar chiller, the TXV bulbs were located at the lower quadrants of the suction line leaving the evaporator.

On this unit, the bulbs are located at the very top of the suction lines. A location I've only used ir seen on quite small systems.

The rule of thumb I've followed in the past (if no data sheets with placement info) is that on small scale systems, with 3/4 or smaller suction lines, the bulb goes at the top and on larger suction lines, the bulb goes at the 4 or 8 o'clock position.

Alco's own data sheet suggests the 4 or 8 o'clock position so I'm curious to the original manufacturer's decision to place the bulbs at the very top of the line.

What changes to the behavior of the TXV will occur with changes to the bulb location?

While I'm curious, I'm a bit hesitant to start moving the bulbs around just to see what happens!