5 hp electric compressor motor replacement


Old 02-03-15, 04:48 PM
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5 hp electric compressor motor replacement

I have a Ingersoll Rand 60 gal 5 hp compressor. The motor is bad. The motor # IR 23378805. I've read that this motor is not very reliable, they catch fire, sometimes don't last more than a month.

Which brand of 5hp 208v/230v compressor motors would be the most reliable? I've seen brands: Ingersoll Rand, Iorntron, Century, Leeson, Baldor.

Anyone know which brands would be the most reliable? Any brands not listed above that would be reliable?

Thanks everyone,
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Old 02-03-15, 07:19 PM
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I've always had good results with Grainger motors. They offer a Century motor as a replacement.

CENTURY Air Compr Motor,5 HP,3450 rpm,230V,56HZ - Air Compressor Motors - 1ATA9|B813 - Grainger Industrial Supply
Old 02-04-15, 09:58 AM
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The biggest problem is not the brand of motor but the fact that "compressor duty" motors are specially made to be cheap. They only achieve their horsepower rating by running in the "service factor" range and as such they run hot and THAT is why they fail. A five horsepower "compressor duty" motor is more likely a three horsepower motor that is overloaded in the compressor duty.

For best results I strongly suggest that you replace the motor with a horsepower rating one size larger. Ideally use a 1750 (1800) rpm motor with a larger pulley in place of the 3450 (3600) rpm compressor duty motor. You will only do it once. You could also use a "farm duty" motor of the same size but with a slightly smaller pulley to reduce the compressor speed to about 80 to 90 percent or so of the original speed.
Old 02-04-15, 03:07 PM
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Thanks PJmax for the Century motor suggestion, I've considered that brand but Furd's suggestion is interesting.

Furd, are you recommending a 6 hp 1750 rpm motor (one size larger)? I've seen 2, 7.5, and 10 HP. Don't remember seeing a 6 hp motor.

Any recommendation for a motor brand?

Also, any websites that might have a calculator for a pulley diameter to keep the pump turning at the right rpm?

Thanks again,
Old 02-04-15, 04:14 PM
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No, you won't find a 6 H.P. motor, but that's okay, because there is enough difference between the "compressor duty" motor that you have now and an actual 5 H.P. motor that you would still come out ahead. As for the motor pulley size, there are a couple of ways you could approach it, but one way would be using this formula...

compressor RPM = (motor pulley pitch diameter times motor RPM) divided by compressor pulley pitch diameter

Now, an air compressor pump is designed to operate at a specific RPM, so you don't want to change that, and you don't want to change the compressor pulley, or flywheel, so keeping those two constants, cutting the motor RPM in half means doubling the pitch diameter of the motor pulley. The pitch diameter is measured where the belt actually rides in the pulley, not at the outside of the pulley.

That said, I agree with Furd, and would have suggested that you buy something with an actual 5 H.P motor to start with, but changing it at this point is going to turn into a fair amount of effort.

First off, the frame on your existing motor is probably something like a 56Z (?), while the larger 5 H.P motor is probably going to be something like a 184T. Frame size establishes the footprint, shaft location, shaft size, etc., so all of those things will change. The table on your compressor may or may not be slotted for a larger motor, and the shaft size and location may require you to alter the beltguard. Also, the "real" 5 H.P. motors that Furd and I prefer require a magnetic starter, which you probably do not have now.

So, practically speaking, I think that PJ offered some sound advice. And air compressors are hard starting, so I would definitely look the wiring over again, to make sure that everything is properly sized.

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