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Direction of compressor flywheel

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This question isn’t an uncommon one if you’re taking care of wiring your own compressor – it speaks to the fundamental question of how an air compressor works, so it’s definitely worth exploring to make sure you don’t make a mistake on the direction of rotation on your compressor…

My older speedaire is a little noisier since i put heavier gauge wires to it.. I might have crossed wired it and it might be running backwards. How do i know which way the flywheel rotates??

I have looked for the directional arrow on the compressore but found none.

I don’t think, personally, that the rotation of the pump flywheel on a smaller reciprocating air compressor makes any difference.

Ultimately, what does the work is the piston moving up and down, and whether the flywheel and the crank shaft are turning one way or the other, the piston will still move up and down.

My .02 cents worth, other opinions are welcome. 🙂

Compressor pump flywheel - what direction is right for air compressor?
Compressor flywheels, often made of cast iron, come in a variety of shapes and sizes. Often the vanes on the flywheel are oriented to move air over the pump to cool it, and that’s a hint to correct motor rotation.


Direction of rotation of compressor pump
by: Anonymous

Oh YES it does matter which direction the flywheel turns.. Have you ever really worked on anything that involves valves, cams, pistons , cranks,and correct timing /// etc.??

The question here is not about an internal combustion engine, and for sure, rotation is critical, but about an air compressor that has spring steel on a plate for valves and no other items that require “timing”.

When the cylinder drops, one valve is shut and the other opens to let in air, and when the cylinder rises, the open valve is pushed shut by air flow and / or the steel returning to rest, and the other opened by the air being compressed and blown into the tank.

If it’s a larger air compressor, the pump may have a sheave adjacent which, with the integral fan blades, will direct air over the pump and cools it. If the compressor has such a sheave, then of course, the rotation is important to ensure that air passes over the pump helping to cool it.

In terms of motor rotation, if the motor is TEFC then there will be a fan an the rear shaft. That fan must rotate so that it directs air over the motor to cool it. That fan rotation direction is the correct rotation for that motor.


Re: Compressor Direction
by: Chris I would say that the compressor would function equally well turning in either direction, but the cooling fan which is usually cast into the flywheel is directional.

Similar to an engine, most flywheels on compressors turn counterclockwise when viewing them, and the cooling fan is designed to blow air across the compressor when spun counterclockwise.


Which direction of rotation
by: George on my Speedaire, the direction of rotation is stamped on the name plate. In my case, the compressor rotates CC.


Compressor pump direction
by: Anonymous Although compressors will produce air in either direction of rotation another factor is that on some compressors there is a dip tube on the bottom of the connecting rod.Some are straight and rotation does not matter except for air flow but some do have a pocket and the rotation has to be in the correct direction so that the pocket picks up the oil to “splash” lubricate the pump internally. These styles of compressors usually have a tapered flywheel with the pump direction stamped on the flywheel.

Care to comment. Please do so, and upload a photo or three to show your compressor rotation.

By Bill Wade

About Air Compressors has been helping folks with their Air Compressor Problems since 2002 online. We're a community of DIY and Compressed Air professionals who are keen to support everyone across the globe with their air compressor issues and troubleshooting. Whether you're trying to identify an old air compressor, or troubleshoot an error code on a sophisticated new industrial air compressor - the community at About-Air-Compressors.com is here to help you

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