# Electric question

Discussion in 'The Okie Corral' started by DAKA, Jun 11, 2020.

1. ### DAKA

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Is there an easy way to determine what size generator will be required for a 4 ton house a/c?

2. ### Ramjet38Mentally Frozen

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3. ### FullClipNative MainiacCLM

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From the interweb....

A 2-ton AC at this SEER rating is approximately 15 amps; 3-tons is 18 amps; 4-tons is 21 amps. ... A typical whole-home air conditioner uses a 240-volt power outlet. Multiply the amps by 240 watts, which equals 4,320 watts....

So in your case, 21 amps X 240 = 5,040 Watts.

BUT bear in mind that the starting requirements (surge) is normally almost twice the normal running amps...so if it was me, I'd be looking at around a 7 or 8KW continuous output unit....but that is JUST the AC.

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4. ### Simi_gun_guy

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You need to look at the compressor unit for the LRA rating. The is the current required to start the compressor. Next would be the load for the blower in your home. I suspect that any generator that can supply enough current to start the compressor will be able to run bothe the compressor and blower. As an off the cuff, I’d bet you’re needing at least 8Kw, maybe 10KW. Look at the the current surge these units can provide.
Good luck with AC on a Gen. It can be done, but it may prove expensive! Just FYI, I believe my unit is also 4T, the LRA is 96A, while running load is 21-22A.

Last edited: Jun 11, 2020
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5. ### walke121

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I’ve always heard to determine which generator to get add up required wattage and the. Double it. So you would want a 10kw if the AC draws 5040w. But I know peak/starting draw and running constant draw.

Sent from my iPhone using Tapatalk

Last edited: Jun 11, 2020
6. ### G26-Has-my-6

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As a point of reference, I have a 5T AC unit, and I was told an 11kW generator would be marginal. I installed a 17kW generator, and it runs everything in the home. I do have all LED bulbs, but I also have 2 refrigerators.

So using rough math, you have 80% the AC unit I have, and 80% x 17kW = 13.6 kW

7. ### thespork

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If you are looking to run serious, 220v appliances like central air, dryers, etc. I would start at no less than 10kw continuous, and probably more...

I have a little 4.5(continuous output)kw dual fuel, but its only good enough to run a refrigerator, a few lights, and a window unit, but probably not all at the same time!

Last edited: Jun 12, 2020
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8. ### rj1939

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Yup, beware of starting amperage.

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9. ### ranger1968

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This, something with 8kw + running watts and a surge in excess of 10 kw....

10. ### FullClipNative MainiacCLM

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12. ### Simi_gun_guy

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FWIW, I tried to sell my wife on a unit like this. She threatened to rip it off the wall & throw it at at me! We ended up with a nice central air system.
YMMV

Ed

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