Why does my aircon trip the inverter when it starts?
A non-inverter aircon’s compressor draws its locked-rotor current for about half a second at every start: 5 to 7 times its running current, 9 kVA for a 1.5 HP unit. An inverter rated 3 kW with a 6 kW peak shuts down on overload before the compressor gets going. A bigger inverter moves the problem to the battery, whose BMS must pass 400 A for that half second. The real fixes are an inverter aircon or a soft starter.
Bakit nag-o-overload ang inverter pag nag-start ang aircon?
Ang compressor ng non-inverter na aircon ay kumukuha ng lima hanggang pitong beses ng running current sa unang kalahating segundo ng bawat start: mga 9 kVA para sa 1.5 HP. Ang 3 kW na inverter ay nag-o-overload bago pa umandar ang compressor. Kung palakihin ang inverter, ang battery BMS naman ang magku-cut. Ang tunay na solusyon ay inverter aircon o soft starter.
See it run
Why a 1.5 HP non-inverter aircon trips a 3 kW inverter at start-upA build with a test sheet: every number on this page is a test you can run.
The numbers
| 1.5 HP non-inverter, running | 1300 W, 6 A |
| Locked-rotor start, 0.5 s | about 9 kVA, 40 A at 230 V |
| 3 kW inverter, 6 kW peak | overload shutdown |
| 6 kW inverter and a 200 Ah battery | the battery BMS (200 A) cuts: the start needs 420 A at 24 V |
| 6 kW inverter and a 560 Ah bank | starts and runs |
| 1 HP inverter aircon | soft start, no surge: runs on the 3 kW inverter |
Questions
Will a soft starter fix it?
Usually. A compressor soft starter (the kind sold for RV aircons) cuts the surge to about 2–3 × running current, which a 3 kW inverter and a 100 Ah battery can pass. Match it to the compressor.
Why does the manual say 6 kW peak if it trips at 9?
Peak ratings are for a few seconds at twice the continuous rating. 9 kVA is three times, and the inverter’s current limit drags its output voltage down as well.
Modified sine or pure sine for an aircon?
Pure sine. A compressor on a modified-sine inverter runs hot and noisy and starts worse.
Does the hybrid at home have the same problem?
Yes; the bench shows a 3.6 kW hybrid riding a 1.5 HP start with its output dragged down to about 160 V for half a second, which is a brownout for everything else in the house.
More questions
- Will my solar run the aircon at night?
- Does grid-tie solar work in a brownout?
- What keeps the Wi-Fi router up in a brownout?
- What breaker and wire size for an aircon?
- What breaker and wire size for a water heater?
- How big a solar panel and battery for a piso Wi-Fi?
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