Ice forms in the evaporator/heat exchanger, eventually blocking airflow and causing high pressure drop or high dewpoint.
1
Hot gas bypass valve (HGBV) failed or misadjusted
CheckEvaporator refrigerant temperature should stay above 33–35°F to avoid ice; check HGBV modulation.
FixAdjust or replace HGBV per OEM manual.
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2
Low refrigerant charge causing very low suction pressure/temperature
highCheckCheck suction pressure/temperature against refrigerant P/T chart for the specific refrigerant used; sight glass for bubbles.
FixLeak-check and repair, then recharge with the correct refrigerant type and charge per nameplate — refrigerant type must never be assumed.
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3
Low airflow/load causing evaporator to overcool
CheckVerify actual flow vs dryer rated capacity; check for closed valves reducing flow.
FixRestore rated flow; verify HGBV compensates at low load.
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4
Thermostat/electronic control sensor miscalibrated
CheckCompare control sensor reading to a calibrated reference thermometer.
FixRecalibrate or replace sensor.
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5
Condensate drain frozen or plugged, backing water into the exchanger
CheckInspect drain line and trap for ice or blockage.
FixClear blockage; ensure drain area is not exposed to freezing ambient without protection.
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Safety
Lockout/tagout before opening enclosures. Verify zero energy. Bleed system pressure before opening any pneumatic connection.