What performance does a generator need to have

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I want to buy a generator powerful enough to allow me to have at least one aircon running even if there is a power failure. The input of my aircons is 2450W. I wanted to buy a generator with a rated output of 3.8 kW and a maximum output of 4.5 kW (this one: https://www.bazaraki.com/adv/2990913_gasoline-generator/) but was told it wouldn´t be powerful enough. Can you explain why it shouldn´t be?

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The inrush, locked rotor current, or starting power for a compressor at rest can be two to three times the rated power of the AC unit.  If the 2.4kW rating you stated is the normal running power requirement, then you will likely need a generator capable of 6kW or 9kW to handle the increased load when the compressor cycles.

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55 minutes ago, JG52 said:

The inrush, locked rotor current, or starting power for a compressor at rest can be two to three times the rated power of the AC unit.  If the 2.4kW rating you stated is the normal running power requirement, then you will likely need a generator capable of 6kW or 9kW to handle the increased load when the compressor cycles.

Would that be the same for all aircons or are there some which would start smoothly rather than abruptly?

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3 hours ago, jeba said:

Would that be the same for all aircons or are there some which would start smoothly rather than abruptly?

 

I'm not going to say that soft-start compressors don't exist somewhere, but I haven't seen any residential or commercial units that have this feature.  I've seen soft-start contactors used on high-volume coolant pumps in chiller plants, but this is because the shock load from trying to move a stationary water column in an eight-inch pipe can be like pounding a steel bar with a very large sledge hammer.

 

If you want to know approximately what the startup current is, you might be able to find an electrician who has a peak-hold, or a logging, ammeter or wattmeter.  The electrician can connect the meter to the mains and wait for the compressor to cycle.  This will be close enough to the load on the generator.

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Thanks for the discouragement:). What about those aircons which don´t work either on full power or not at all but proportionally, depending on the temperature gradient (forgot how they´re called). Would those be suitable?

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As far as I know, the compressors have only one speed and are either on or off.  The compressor's job is to turn the low pressure refrigerant from the interior evaporator coils, which now contains the extracted heat from the room, into high pressure refrigerant.  The compressor then pumps the refrigerant over the exterior compressor coils to remove the heat.  The amount of room cooling is determined by the fan speed over the evaporator coil and the cycle time of the compressor.

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