A hunting expansion valve opens wide, floods the coil and drops superheat to near zero, then clamps down and lets superheat soar, over and over. Causes include an oversized valve, a bulb mounted in the wrong spot or loose, flash gas in the liquid line, and very light loads. Watching superheat on a data logger for several minutes is the way to catch it.
Superheat's bouncing between 2 and 20 every minute, the TXV's hunting, check where that bulb is clamped.
Also heard as
- TXV hunting
- valve hunting
Related terms
TXV
Thermostatic expansion valve: a metering device that adjusts refrigerant flow to hold constant evaporator superheat.
Superheat
How many degrees refrigerant vapor is above its boiling point at the pressure it is at.
Floodback
Liquid refrigerant returning continuously to the compressor through the suction line while the system runs.
Starved
Describes an evaporator not getting enough refrigerant, so part of the coil runs warm and superheat is high.