Three Phase Rotation

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A/A Fuel GTX

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WI & AZ
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Electrician
Is it possible for a three phase Air Conditioner compressor to run backwards if the phasing has been altered?
 

norcal

Senior Member
If it's a scroll compressor it's noisy if rotation is incorrect,if a piston type what difference does it make? But as a disclaimer, I use a rotation meter on the supply & make sure it will run correctly.
 

iwire

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Scroll compressors will be damaged by incorrect rotation. Most have labels requiring rotation verfaction at start up.

On the other hand the piston type works either way. However I have been told reversing the direction of an existing unit accelerates the wear of the unit. Take that for what it's worth.
 

Johnnybob

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Location
Colville, WA
Scroll compressors will be damaged by incorrect rotation. Most have labels requiring rotation verfaction at start up.

On the other hand the piston type works either way. However I have been told reversing the direction of an existing unit accelerates the wear of the unit. Take that for what it's worth.
That's kinda weird! I would think you could actually extend the life. Different wear pattern, and all. Kinda like flipping a drive sprocket on a dirt bike, puts the wear on the other side, if you will.
 

K8MHZ

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Michigan. It's a beautiful peninsula, I've looked
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That's kinda weird! I would think you could actually extend the life. Different wear pattern, and all. Kinda like flipping a drive sprocket on a dirt bike, puts the wear on the other side, if you will.

I raced dirt bikes for a couple years and found that flipping the sprockets would destroy the chains and did almost nothing to prolong sprocket life.
 

Johnnybob

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Location
Colville, WA
I raced dirt bikes for a couple years and found that flipping the sprockets would destroy the chains and did almost nothing to prolong sprocket life.
While I neveer raced 'em, I rode/ride them all my life. And yes, flipping the sprocket does almost double the life. You just can't wait till they are all hooked over. Just include it in scheduled maintenance:happyyes:, don't wait till they're all rolled over:happyno:.
Sorry, bit off topic!
 
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JFletcher

Senior Member
Location
Williamsburg, VA
That's kinda weird! I would think you could actually extend the life. Different wear pattern, and all. Kinda like flipping a drive sprocket on a dirt bike, puts the wear on the other side, if you will.

Reduction gears in ships have a gear ratio (say, 19/37) that causes all teeth on one gear to contact all of the teeth on the other before any one tooth touches the same tooth - this extends life. However, in a piston engine (or compressor) running one direction, the cylinder and piston will develop greater wear in one direction (angle of thrust) than the other. Reversing direction would cause basically double the wear and loss of compression, greater oil use, etc.

I suppose whether or not an AC compressor would have reversed heat/cool functions would be dependent on how it was built. A two stroke dirtbike engine can run backward, but it doesnt mean it will suck the intake charge thru the expansion chamber and exhaust it from the carbuerator.
 

Johnnybob

Senior Member
Location
Colville, WA
Reduction gears in ships have a gear ratio (say, 19/37) that causes all teeth on one gear to contact all of the teeth on the other before any one tooth touches the same tooth - this extends life. However, in a piston engine (or compressor) running one direction, the cylinder and piston will develop greater wear in one direction (angle of thrust) than the other. Reversing direction would cause basically double the wear and loss of compression, greater oil use, etc.

I suppose whether or not an AC compressor would have reversed heat/cool functions would be dependent on how it was built. A two stroke dirtbike engine can run backward, but it doesnt mean it will suck the intake charge thru the expansion chamber and exhaust it from the carbuerator.
Not sure I'm following that line of thought. If the crank, or drive, were not centered on the cylinders, I could see that, but the cylinder would have to be oversized, or egg shaped for the connecting rod to travel further to the side of the cylinder on the compression stroke than the return stroke? Other wise, what difference would it make? Angle of thrust would be the same in either direction:??
And where doese asperation come into the conversation? I thought we were talking about a compressor?
 

GoldDigger

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A bit like reversing the rotation direction of some radial tires?
Reversing compressor rotation results in different wear aress and at best could require a new "break-in period" of gentle use.
 

Johnnybob

Senior Member
Location
Colville, WA
A bit like reversing the rotation direction of some radial tires?
Reversing compressor rotation results in different wear aress and at best could require a new "break-in period" of gentle use.
That is exactly the train of thought I had! If you change direction, change wear area, thus prolonging the life of the machine. Just like new, but different lol
To use the dirt bike analogy again, it's like a rear tire. You have a throttle side and a brake side. Whether you spend more time on the brake, or on the pipe, flip it around and you've got a new tire:D.
 

JFletcher

Senior Member
Location
Williamsburg, VA
Not sure I'm following that line of thought. If the crank, or drive, were not centered on the cylinders, I could see that, but the cylinder would have to be oversized, or egg shaped for the connecting rod to travel further to the side of the cylinder on the compression stroke than the return stroke? Other wise, what difference would it make? Angle of thrust would be the same in either direction,

My apologies: The angle of thrust and momentum is most extreme when the crankpin is at 90 or 270* (perpendicular to plane of reciprocating action) depending on rotation direction. In a piston compressor, a motor is turning circular motion into reciprocating via a crankshaft and rod. The rod is not being pushed just up and down, but side to side as well - this translates to one face or side of the cylinder wall receiving more mechanical pressure than the other, and hence more wear over time. This wear is not even due to compression cycle being 'harder' on the eqpt, and that pulling a piston thru a bore is not the same as pushing one. The walls of the cylinder go out of round (taper) over a period of time from this wear.

In engines, the compression/combustion is the prime mover, so wear occurs in different spots. Pistons with short skirts, and highly oversquare (bore>stroke) designs suffer more from this.

Aspiration was just an attempt to show that while rotation can be reversed, the function of the parts may not be.
 

Johnnybob

Senior Member
Location
Colville, WA
My apologies: The angle of thrust and momentum is most extreme when the crankpin is at 90 or 270* (perpendicular to plane of reciprocating action) depending on rotation direction. In a piston compressor, a motor is turning circular motion into reciprocating via a crankshaft and rod. The rod is not being pushed just up and down, but side to side as well - this translates to one face or side of the cylinder wall receiving more mechanical pressure than the other, and hence more wear over time. This wear is not even due to compression cycle being 'harder' on the eqpt, and that pulling a piston thru a bore is not the same as pushing one. The walls of the cylinder go out of round (taper) over a period of time from this wear.

In engines, the compression/combustion is the prime mover, so wear occurs in different spots. Pistons with short skirts, and highly oversquare (bore>stroke) designs suffer more from this.

Aspiration was just an attempt to show that while rotation can be reversed, the function of the parts may not be.
Ah, thank you! I was trying to see how that double damage would happen, as you would now be wearing on the other side of the cylinder. I'm no engineer, just a lowly sawmill 'lectrician, but when something doesn't make sense, my brain will worry at it like a dog on a bone, till I can figure it out.
 
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