TXV Superheat Maladjustment — Hunting or Liquid Slugging

Question

Accepted Answer

Spring too loose — liquid refrigerant enters compressor (liquid slugging). Check: Measure actual superheat: clamp thermometer on suction line + low-pressure gauge; superheat = suction pipe temp − evaporating saturation temp; superheat below 3°C indicates liquid slugging risk What to do: Adjust TXV screw clockwise (CW) 1/4 turn at a time → wait 15 min → re-measure; target superheat 4–8°C (refrigeration) or 5–10°C (air conditioning) Spring over-tightened — restricted refrigerant flow reduces capacity. Check: Superheat above 10°C + reduced capacity → suspect over-tight spring; suction pressure lower than normal and no frost on suction line What to do: Adjust TXV screw counterclockwise (CCW) 1/4 turn at a time → wait 15 min → re-measure; stop adjustment when superheat reaches target range Bulb improperly positioned — false superheat signal. Check: Check if bulb is mounted at frost/condensation point or on underside of suction line → confirm 12 o'clock position and insulation contact What to do: Remount bulb at 12 o'clock → fully wrap with insulation → recheck after 15 min to confirm hunting resolved

TXV Superheat Maladjustment — Hunting or Liquid Slugging

Likely causes

Spring too loose — liquid refrigerant enters compressor (liquid slugging)

Spring over-tightened — restricted refrigerant flow reduces capacity

Bulb improperly positioned — false superheat signal

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