R-Pro › Field cases › Air conditioning
3-Phase Wiring Reversal — Compressor Rotation Check
Likely causes
Scroll/rotary compressor needs single direction
Check: On 3-phase 380V AC systems (10HP+/industrial), if R-S-T phase order is swapped, compressor reverses. Symptoms: ① start → abnormal noise/vibration within 30 sec → OL trip. ② HP/LP unchanged (no compression). ③ Discharge temp doesn't rise. Verify with phase sequence indicator or multimeter. Common after new install or electrical work.
What to do: Use phase sequence indicator — confirm R-S-T clockwise. If reverse, swap any 2 phase wires (e.g. S-T). After correction, wait 5 min compressor protection time before restart. Manual OL reset may be required. Industrial (50HP+) should have phase-loss protection relay (PSR).
1-phase 220V or inverter type has no reverse-rotation concept (DC compressor + internal inverter control phase). Only 3-phase fixed-speed applies. 'It runs but doesn't cool' just after install = #1 suspect reverse rotation. Phase indicator costs ~₩50-100k — essential tool for 3-phase techs. Can't judge rotation by motor contactor appearance.
All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.
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