DX Evaporator Multi-circuit Maldistribution — Superheat Imbalance Between Circuits

Question

Accepted Answer

Distributor nozzle clogging or partial blockage of some holes. Check: Inspect with instruments or visually What to do: Measure superheat at each circuit outlet: compare outlet pipe temperatures; normal 5–8 K, imbalance if deviation ≥ 3 K Non-uniform two-phase refrigerant velocity. Check: eccentric inlet header installation What to do: Remove distributor and clean each nozzle hole visually and with wire; purge with nitrogen reverse pressure if debris found Gravity bias due to coil height/length differences between circuits. Check: Inspect with instruments or visually What to do: Check TXV opening — readjust superheat setpoint to 5–6 K and restore overall flow first Insufficient TXV opening. Check: overall refrigerant flow deficiency What to do: Verify refrigerant charge — no bubbles in sight glass + subcooling 5–8 K, then top up in small increments Excessive gas entrainment at distributor inlet due to refrigerant shortage. Check: Inspect with instruments or visually What to do: Check distributor inlet pipe inclination and reinstall level (maintain vertical inlet flow into header)

DX Evaporator Multi-circuit Maldistribution — Superheat Imbalance Between Circuits

Likely causes

Distributor nozzle clogging or partial blockage of some holes

Non-uniform two-phase refrigerant velocity

Gravity bias due to coil height/length differences between circuits

Insufficient TXV opening

Excessive gas entrainment at distributor inlet due to refrigerant shortage

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