Does it matter which direction the compressor pump is rotating?

Published Categorized as Air Compressor Pump, Notebook 4 Comments on Does it matter which direction the compressor pump is rotating?

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This question came in and speaks to the fundamentals of how does an air compressor actually work? Without further ado, here’s the question…

I have a Dayton compressor and the motor is rotating counter clockwise.

Does it matter which direction the compressor is rotating?

Can the compressor rotate either direction and work properly?

Friend, the motor shaft is turning a crankshaft that converts rotary motion into linear motion of the piston inside the cylinder.

Regardless of which direction of rotation the crank is turned, it will still generate the same reciprocating movement of the piston in the cylinder.

If there no other actions being driven by the crank except the piston reciprocating, then I don’t think the direction of rotation matters, except where the pump sheave has fan blades build it. In that case the sheave would rotate so that air flow generated would blow over the pump, cooling it.

So, if it were my air compressor, and if, for some reason, I had a motor with a shaft that was rotating in the opposite direction, I would not worry about changing the motor rotation. But then, that’s just me.

To be absolutely sure, why not contact Grainger (see Speedaire page) as I believe the Dayton brand is their air compressor, and get the info direct from them? If you do, others would like to know, so please post a comment here.


Yes rotation matters on some compressors
by: Anonymous

The direction of rotation is indeed a factor on pressure lubed compressors and the direction of rotation could matter on a splash lubed compressor if it is designed with a flap or splasher internally to that may only work when it turns correctly.

The actual pumping of the compressor may not be affected at all in either of these cases and you will only see the problem arise when it starts knocking or locks up.

The direction of the pulley also matters since it acts as the fan to move air across the pump to help cool it and could affect it that way also.

Normally if a pump is designed to rotate a certain direction the pulley will have a directional arrow on it in some form.


by: Anonymous

yes u r right……


by: Bill

Yup. No argument from me.

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I am installing a 3 phase compressor that once was working. It has a rotational arrow and I now have it phased the right way and it just locks up.What am I doing wrong.It will run great backwards but when I change the phases to the right it stops. Help!

Might be the thing has a replacement sheave, and the arrow is wrong. What kind is it? Most, but not all with work either way (but may possibly overheat). Sounds like yours is picky, and probably should go the “wrong” way. Maybe send a few pix?

It is a Dayton Air compressor with both CCW on the name plate and an Arrow stamped on the pump housing. It is 3 phase and the motor works fine with the belt off, running at 6 amps per leg. Could something be broken inside the cylinder head. Thanks Jeff

Jeff, by what kind I mean is it a reciprocal (piston) type, rotary vane, screw, centrifugal or what? And is it pressure lubed? I’m guessing piston now, since you mention cylinder head. Is it single stage or multi-stage? (pix would tell me most of this)
6 amps running the motor no load? What HP is it rated?
Before you suggested the pump runs backward without the motor stalling. Is that right?

Again, pix please, absent a model number.