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Compressor Liquid Compression Low-Frequency Pulsation → Pipe Rumbling

Likely causes

Liquid refrigerant enters suction at startup → liquid compression shock below 10 Hz

Check: Check suction pressure before startup — above saturation pressure suggests liquid pooling; verify crankcase heater works (30-minute preheat mandatory); measure TXV/EEV superheat — below 5 K indicates excess liquid refrigerant

What to do: Replace crankcase heater if faulty → preheat 30 min before startup; tighten TXV (clockwise 1/4 turn increments) or adjust EEV superheat parameter upward; stop immediately if severe vibration at startup (even one liquid compression event can damage compressor valves)

EEV superheat setpoint too low (below 5 K)

Check: Calculate superheat from suction line temperature minus suction saturation temperature — below 5 K is overloaded; check for refrigerant overcharge (proper subcooling 5–8 K range)

What to do: Adjust EEV superheat target to 5–8 K; remove suction line pipe traps or consider installing suction line accumulator; if pipe rumbling is severe within 3 minutes of startup, stop immediately → turn on crankcase heater and wait 30 minutes before restart

Field tip

If pipe rumbling is severe within 3 minutes of startup, stop immediately — turn on crankcase heater and wait 30 minutes before restarting.

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