Originally Posted by vintagecar
how do you figure the HP to Amp ratio to find out what the true HP is
Volts X Amps = Watts
746 Watts = 1 HP
But there's a lot of things to consider so it will never be an exact conversion when looking at motor ratings. Basically when you are looking at these single stage compressors with a 60 gallon tank most, if not all, will be 15 Amps or about 3 HP. A real 5 HP motor will be rated at least 21 Amps and can be more and any thing above a 21 Amp rating will have a believable HP rating anyway because then you are talking industrial types. Also the better companies are honest about the power ratings, for example Quincy numbers are believable as are Eaton's but IMHO Eaton has other issues that would cause me to avoid them totally. Ingersoll Rand is a very large company but even their 5 HP and smaller compressors have some very suspicious numbers so I would approach them with caution also. Of all places to find a good compressor the US General 2 stage at Harbor Freight is on sale quite often in your price range. These things are NOT made in China, the pump is from Italy and most of the rest of it is made right here in the USA where it is assembled. I have no first hand experience with these HF compressors but the US General I looked at last year had a USA made motor and electrics and later I discovered that even the tank is US made, it actually looks like a really decent outfit and when on sale they can be bought right! Use one of the weekly E-mail 20% coupons along with the sale price and these things can be bought dirt cheap!
I have not used one of them, in fact I have never even heard one run but they look like a decently built unit and the parts quality looks to be a lot better than the McHome store types.
Those 20% off coupons can be found in a lot of sports and gun magazines also and with one of them that compressor is less than $700! I had not even realized those things could be such a deal until I looked them up just a bit ago, use that coupon when they are on sale in the store and we are talking a 22 Amp (5 true HP) 2 stage 60 gallon outfit for only a very few dollars more than those 3 HP units.
[EDIT] My mistake, it is the 7 1/2 HP compressor that has the Baldor USA made motor on it. Not sure where the 22 AMP 5 HP motor is made but it is an AO Smith brand.