dewalt 3hp exteme will not build air

will not build air at cutin (75

)psi motor stalls and hums

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Bill says...

Drain the tank, turn the air compressor back on, and monitor the unloader valve to be sure that it works when the pressure in the tank reaches normal cut out levels.

Or, if the compressor won't start with zero pressure in the tank, and assuming that you are not using an extension cord and that the power supply to the compressor is clean, you might have a start capacitor failing.

Maybe let me know as a comment here?

Thanks,

Bill

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cut in motor hums

builds pressure in empty tank but motor hums when time for cut in at 75 psi

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Bill says...

Not a lot to go on here. I'm understanding that the compressor starts and runs fine to normal cut out, and then, when using air, when the tank pressure drops to the normal cut in of 75 PSI, the motor cannot start.

For a start, go to the SITEMAP page and click the link to UNLOADER VALVES.

This, from the sound of it, is likely your problem.

Cheers,

Bill

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increasing psi on my DeWalt compressor

by dan
(minneapolis mn)

Hi I have a Dewalt 8hp 125psi 17 gallon "hot dog" style 16.2 cfm@100psi. compressor model# D55275.

I want to bump that up to 150 psi.

can I change the unloader valve or any other components to make it put out 150PSI?

The unloader valve says 110/125 on it so changing that should work i am guessing? The regulator is capable of 150psi.

I also have a smaller 5.5hp dewalt with a 10 gallon tank and that one cuts off at 150 psi. everything about that compressor is smaller
thanks

Dan

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Bill says...

Dan, it's always a trade off between pressure and flow. Usually, the higher the flow, the lower the available pressure, and the reverse is true as well, the lower the output flow the higher the pressure the compressor can generate.

Your compressor has been built to deliver the 17 CFM at 100 PSI it says it will. Although, I must admit, there must be something a bit unique about the design, as compressors quite often deliver 4 CFM of compressed air flow at 90 PSI for each HP of motor size.

It's not the unloader valve that determines the pressure rating of your compressor.

It's a combination of electro/mechanical design whereby the components of the compressor, working together, output that pressure.

You can experiment with turning up the high pressure cut out on the pressure switch, and you can experiment as well with different sheave sizes to try to increase pressure.

I recommend neither. Your compressor was built to deliver what it does, and modifying it will first, probably void any warranty, and second, could have disastrous results.

Cheers,

Bill


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