Abnormally High Discharge (High-Side) Pressure — 4 Major Causes

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Dirty condenser coil — dust, oil, lint blockage. Check: Inspect condenser coil with flashlight — check fin gaps for blockage. Normal airflow 2–3 m/s; ≤0.5 m/s means severe blockage. Coil inlet-outlet temp difference normally 5–8°C; >10°C suggests blockage. What to do: 1) Spray coil cleaner (alkaline or acidic) and rinse. 2) Restaurants, laundries, factories require cleaning within 6 months. 3) After cleaning, straighten bent fins with fin comb. 4) Set up recurring cleaning schedule. Condenser fan failure or low motor RPM. Check: Visually and audibly verify fan rotation → if stopped or slow, inspect motor and capacitor. Measure RPM with tachometer — >5% deviation from rated indicates issue. Also inspect blade damage or foreign object jamming. What to do: 1) Measure motor winding insulation with megger (≥1MΩ normal). 2) Test start/run capacitor capacitance — within ±6% is normal. 3) Replace motor if bearings damaged. 4) Replace blade immediately if cracked or rusted — flying debris risk during rotation. Refrigerant overcharge — liquid line full, condenser partially flooded. Check: Measure subcooling — >15°C strongly indicates overcharge. Touch lower section of condenser; large cool zone (liquid-flooded) confirms. Compare actual charge vs nameplate spec. What to do: 1) Recover charge in 200g increments with recovery machine — wait 5 min between each, remeasure. 2) Repeat until subcooling 5–10°C and high-side normal. 3) Document overcharge cause in service report to prevent recurrence. 4) Store recovered refrigerant in recovery cylinder; can reuse after precise weighing. Non-condensable gas (NCG) contamination — inadequate evacuation or air ingress post-leak. Check: After shutdown stabilization, if condensing pressure is >0.3 MPa above ambient saturation pressure, NCG strongly suspected. Pulsating high pressure during operation also signals NCG. What to do: 1) Recover all refrigerant. 2) Evacuate with 2-stage vacuum pump to ≤500 microns — 3+ hours. 3) Hold vacuum 30 min — rise within 50 microns acceptable. 4) Recharge by weight, verify pressure stabilization.

Abnormally High Discharge (High-Side) Pressure — 4 Major Causes

Likely causes

Dirty condenser coil — dust, oil, lint blockage

Condenser fan failure or low motor RPM

Refrigerant overcharge — liquid line full, condenser partially flooded

Non-condensable gas (NCG) contamination — inadequate evacuation or air ingress post-leak

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