air compressor question

[Steve Dunbar]

rb wrote: ...

...

The horsepower ratings on compressors are often wildly exaggerated. There should be a nameplate on the motor showing how many amps it draws.

-- Steve

[rb]

OK Gang---help ease me over the hump here. The hump I'm referring to is a big concern in my gourd about whether or not I can power a 5 hp electric air compressor. The motor is 120v only; no 220v option.

When I look at 5 hp, that comes out to approx 3.8kw in electrical power (750 watts/hp). At the 110 line voltage, this computes out to a draw of approx

35 amps at the 5hp load. Start surges will exceed this.

I have no idea where I will find a 110v 35 amp line around my house. The big question is whether my numbers are right or not. If they're right, then I simply won't be able to power the air compressor without running a new, dedicated line which it's not worth doing. I only need about a 2hp compressor, but had found a super deal on the 5hp one---sort of.

[wayne]

check the specs on the unit I have a 6 hp 120V 15 AMP sears compressor that work fine. It does have a short fat cord though!

Wayne

[Lawrence Wasserman]

Forget about computing the current draw from the compressor HP. The HP figures are not accurate or realistic and in most cases are for marketing purposes. Check the documentation or look on the compressor itself, probably on a plate mounted on the motor, for the actual current draw. If the compressor was factory supplied with a 120V plug it's a good bet that it won't need more than a 20 amp circuit.

[rb]

OK. The deal is that I really can't check the motor plate. The units are sold by a nationwide mailorder firm, and the boxed units are sealed, in a warehouse somewhere. The tech at Customer Service only has a dinky spec sheed which only says it a 5hp 110v motor. No amps given.

I sort of suspect that the rating may be significantly exaggerated, and that I can get by on a standard 15 amp circuit. Also, I won't be demanding the absolute max pressure as a steady state draw, so probably should be able to get by on a lot less hp.