Refrigerant Undercharge/Overcharge — Winter-Specific Symptoms

Question

Accepted Answer

[Undercharge] Leaks accumulated during summer manifest as first symptoms entering winter. Check: excessively low suction pressure What to do: After heating mode stabilizes (15 min), simultaneously record HP, LP, suction superheat, and discharge superheat → distinguish undercharge vs. overcharge pattern [Undercharge] Frost zone on suction pipe shrinks + suction superheat increases to over 10°C. Check: Inspect with instruments or visually What to do: [Undercharge check] R-410A standard: at 0°C outdoor during heating, LP should be ~6.5–7.5 bar; deviation indicates undercharge → detect leak and recharge [Overcharge] Charged to summer cooling mode standard. Check: risk of liquid refrigerant entering compressor during winter heating What to do: [Overcharge check] Repeated HP trips over 27 bar + suction superheat 0–2°C → liquid refrigerant risk; recover some refrigerant then remeasure [Overcharge] High pressure rises excessively (over 27 bar for R-410A). Check: repeated high-pressure trip What to do: When adding refrigerant, simultaneously monitor outdoor temp, suction superheat, and liquid line subcooling (target 5–8°C) → add in small increments Refrigerant added without a reference standard. Check: especially difficult to judge on inverter units due to load fluctuation What to do: For inverter units, switch to maximum frequency lock mode (service mode) before charging measurement — stable load conditions are essential

Refrigerant Undercharge/Overcharge — Winter-Specific Symptoms

Likely causes

[Undercharge] Leaks accumulated during summer manifest as first symptoms entering winter

[Undercharge] Frost zone on suction pipe shrinks + suction superheat increases to over 10°C

[Overcharge] Charged to summer cooling mode standard

[Overcharge] High pressure rises excessively (over 27 bar for R-410A)

Refrigerant added without a reference standard

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