tev bulb

[angryk]

i would greatly appreciate it if some one can explain proper tev bulb mounting and why it is important. does it matter if it is mounted verticaly or horizontaly?

[Prof Sporlan]

Conventional wisdom is to place the bulb on a horizontal free draining suction line close to the outlet of the evaporator, and at a 4 or 8 o’clock position, with 12 o’clock being the top of the line.

At low refrigerant velocities in the suction line, which are not untypical of refrigeration applications, or large a/c systems with unloading compressors, oil will tend to separate from the refrigerant vapor flow, and flow along the bottom of the line. So you do not want to locate the bulb at the 6 o’clock position, which will cause the TEV to starve. Obviously, you want the suction line to be free draining at the bulb location for the same reason.

On large suction lines, say 1-1/8” OD and greater, you can also develop a significant temperature gradient from the bottom to the top of a horizontal free draining suction line. In other words, the temperature of the top of the suction line can be significantly greater than the bottom of the line at sustained low refrigerant velocities. As a result, the 4 or 8 o’clock position provides a good average temperature for the TEV bulb to sense.

Placing the TEV bulb on vertical suction lines should be avoided whenever possible. You can get odd temperature readings, particularly at low refrigerant velocities.