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Air Compressor Horsepower/Wattage/Amperage
I thought I had this compressor power thing down to a pretty good science
until they started screwing around with "rated watts" and "peak power" and all that crap that makes their compressor look really good until you go to use it. Back when we were using "real" horsepower I used a figure of 750 (to make it easy to calculate, I believe 746 is the actual number) watts per horsepower and an efficiency factor of 85% so that a one horse motor would take 860 watts to do the actual work. But then you multiplied that times two for "starting" wattage for a couple of seconds to give 1725 watts under start and then times three for starting under some volume of air left in the compressor reservoir or about 2600 watts. That presses my 2200 watt continuous duty (2800 watts peak) fairly close to the load limit, but certainly gives a margin for error that seems reasonable. Before I tell elebendy bazillion Kitplanes readers that the Harbor Freight Subaru 2200 watt generator will drive the Sears 1 horse compressor (and even worse, buy the Sears compressor only to not have it work), will somebody please do a reality check on me for horsepower/watts for this lashup. (Note ... convert watts to amperes by dividing watts by 120 volts). 860w=7a 1725w=14a 2600w=21a Sears and Harbor Freight are damned near clueless about this sort of stuff. If anybody has a source I can reference for running/starting/starting under load for air compressors it would be well received. I'd LIKE to buy a 3/4 horse compressor but they go from the kiddie's 1/4 horse toy straight to one horse with darned little in between. Jim -- "Dream as if you'll live forever. Live as if you'll die today." --James Dean |
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