Increasing the starting torque (un-seize) a CA compressor...

Thanks! It was surprising how much more torque was possible, actually.

Great video, David! Fascinating to see the tabulated results. I was surprised that the starting cap didn't increase the torque at 120V as much as I expected. I was also previously worried about GE's recommendation of applying 240V - but you've shown the windings won't go up in smoke by the time it starts (or should start!). The two phase starting should be very easy to implement in my part of the world since the mains supply is three phase 240/415V. Hopefully, I won't ever need to try it.

Thank you TURBOKINETIC ! Super job of using visual aids and putting the different electrical configurations for unseizing the CA compressor into perspective.


When I opened the seized CA compressor that I had seize on me I found it to be locked up solid. Using a back and forth movement using the top mounted fan as a handle I was able to create a tiny rotational movement that I was able to gradually expand until it grudgingly completed a full rotation. At the same spot of each rotation there was a perceptible drag. When I completely disassembled the compressor I found copper plating on various steel surfaces. The drag I had felt when rotating the fan was caused by a deposit of copper plating on the bottom surface of the rotor/ compressor assembly. That deposit of copper plating had reduced the end play (up/down) movement to zero which had seized the assembly. I placed a piece of PLASTI GAGE on that deposit and reassembled the compressor to measure the end play after I had unseized the machine and it measured less than .001. PLASTIGAGW will only measure down to .001. This is shown in these links.


monitortop.freeforums.net/thread/824/observations-opening-ca-compressor-stuck

monitortop.freeforums.net/thread/868/lard-oil-copper-plating


My inch/lbs hand torque meter had a provision so I could put a T handle on it so it would be like using the top mounted fan on the compressor to measure my wrist torque. I clamped the Torque meter into a vise and using my wrist on the T handle I approximated the maximum torque I would have used in a back and forth movement to free the compressor. The black dial on this torque meter shows 33 inch lbs which is just under 3ft/lbs which approximates the 2.4 ft/lbs and 2.9 ft/lbs obtained from your 240 volt trials. In comparison the .620 ft/lbs and .71 ft/lbs you obtained using 120 volts were comparatively just nudges to obtain 6 - 8 inch/lbs with my wrist.


drive.google.com/drive/folders/1jXKjdQ0sh9buVRY8HYKKcoUc1ISw6ia6


Cablehack had earlier suggested reversing the 120 volt motor by switching the wiring and putting a capacitor in the run winding. That way a person could create a back and forth movement to free the compressor. Thanks to your measurements I can see that the back and forth nudges might not be enuf and the 240 volts torque measurements were closer to the torque I probably used with my wrist.


I never had a need to experiment with electric motors. Is there a way to reverse the 120 volt motor with the 240 volts applied so that a person could loosen the motor with a back and forth movement?

Thanks for the quick reply. Thanks to your measurements If I were to obtain another seized CA I would not hesitate to apply 240 volts in an effort to unseize it. I would though add and remove the capacitor into the run winding alternating back and forth even if the reversal was weak. It would allow the forward rotation to obtain a momentum against the seizure.

I had cut the top open so I could remove the compressor so that the top would be lighter. I had the thought that in case I modified a machine with a condensing unit mounted elsewhere I would be able to have a lightweight top to make the machine look original. The motor did not weigh much and the top was still almost as heavy. The metal was stored outside and rusted and all of it went to a scrap collection.

Much or most of my refrigeration HVAC experience was with semi-hermetic compressors with oil level site glasses and oil drain plugs. With most compressor replacements we would typically test the oil with a Sporlan acid test kit to check for acidity. If the test showed the oil was acidic we would use filter driers rated for acid removal changing them often. Semi hermetic compressors have oil drain plugs so we would often change the oil maybe several times. We would declare the job done after a sufficient run time and an acid test kit showed it was no longer acidic.


According to this link SECTION 10 - methyl formate decomposes into carbon monoxide and carbon dioxide and formic acid and methanol

fscimage.fishersci.com/msds/97142.htm


Hence the Formic Acid in the compressor would make the mineral oil acidic resulting in copper plating:

"Copper pennies are useful in demonstrating the concept of copper plating. A simple lemon bath is used to demonstrate this process. Lemon juice is a natural acid that attacks the oxidized copper-oxygen bond, releasing it from the surface of the pennies. Placement of a metal such as an iron nail in the lemon bath containing suspended copper ions results in a simple copper plating of the iron nail."

en.wikipedia.org/wiki/Copper_plating


I would suggest that maybe copper plating could not take place if a CA compressor  were in constant use and could only happen if it sat idle for an extended time?

When I opened up the CA compressor that had seized I was astonished at how shiny the copper was which in hindsight was probably caused by being in contact with acidic oil.

It would be interesting to test the oil for acidity from a CA compressor that had seized.

I remember seeing those pictures. That is vile! So glad it didn't also attack the compressor motor in some way. But after 7 years if that had happened it would have made its self known by now. 

And again it's worth repeating how nice your restored unit and cabinet looks.