Compressor won't start.

[Backyardactech]

Hi guys. I've got a walk in freezer unit with a Tecumseh AVA2490ZXT pump that won't start when energized. I'm tried of my dad telling me to change these things without fully understand what went wrong.

208-230
3 phase

Actual voltage and current at start
L1 207.8 0.0 amps
L2 208 0.0 amps
L3 208 0.0 amps

My problem--or lack of problem--is that no windings are open or shorted to each other, nor to ground. I get exactly 2.0 ohms between each winding. The compressor was hot on arrival, I cooled it with cold water until I was confident it should run. The internal thermal protection is what confuses me. How is this checked? Does it not cause one or two of the windings to open and shouldn't I get and OL reading when checked?

Again that's what I'm trying to figure out. I read a bit about using a Megger to officially rule out bad windings, but I don't know one. Is this what I should do in the future? I want to do things properly

Thanks for any help and tips, and I love this site.

David

[Backyardactech]

Sorry for the typos.. Sent from my phone and it's tough to proofread in the sunlight

[Backyardactech]

Tried = tired
Don't know one = don't own one

[install monkey]

disconnect the compressor leads and prove your getting 3 phase accross them- with them connected to the pot they can give a back feed, ensure compressor body is cool and retry- sometimes contactors can pit to cause this issue

[Backyardactech]

I've visually and 'tug-tested' each female flag terminal that connects to the compressor, I even replaced one that felt a little loose. Removed the leads from the compressor and verified 3 phase power (each around 210vac).

Right now I have left the 2 fans running air over the compressor body with the leads taped off to cool it once more while I grab lunch. I'm still on site. I'll leave water trickling over it as well

[install monkey]

Voltage Range (50 Hz):
180-242


Voltage Range (60 Hz):
180-254


Locked Rotor Amps (LRA):
65.1


Rated Load Amps (RLA 50 Hz):
N/A


Rated Load Amps (RLA 60 Hz):
7.4


Max. Continuous Current (MCC in Amps):
15.4


Motor Resistance (Ohm) - Main:
1.58

[Tayters]

Hi David,
Sounds like you have an internal klixon (yeah, painful see a doctor...) and the compressor is seized.

using a Megger to officially rule out bad windings.
A megger will only prove windings aren't shorting to earth. No real way of proving motor is seized until you've proved all phases are present (or starting gear is alright if a single phase unit) and motor still takes LRA.


My problem--or lack of problem--is that no windings are open or shorted to each other, nor to ground. I get exactly 2.0 ohms between each winding. The compressor was hot on arrival, I cooled it with cold water until I was confident it should run. The internal thermal protection is what confuses me. How is this checked? Does it not cause one or two of the windings to open and shouldn't I get and OL reading when checked?
Bit hard to test other than windings ohm fine but take no current and motor getting hot. Causes all windings to go open circuit and is at the star point (or I guess at each 'corner' of a delta wound motor). Comp must have been taking current to get hot in the first place. Bigger motors have the klixon wired into the control circuit so can be sensing heat on one phase only.

L1 207.8 0.0 amps
L2 208 0.0 amps
L3 208 0.0 amps
Like this then!

Cheers,
Andy.

[monkey spanners]

Swap the phases and see if it will run in the opposite direction temporarily like this,

https://www.youtube.com/watch?v=EpOZXEfByfE

This one had a snapped rod so pulled run current then locked rotor, eventually would go off on the klixon.

[Backyardactech]

Hi David,
Sounds like you have an internal klixon

Got it, thanks.

Of course no go on that compressor ever starting back up. It was replaced with a perfect match up and everything went smoothly. Because I didn't fully understand what faulted on the old pump I treated it as a burn-out and took all precautions.

I guess my initial thoughts were correct, but I wanted something testable to prove my theory.

Thanks for all the additional information. I'm here to learn so I truly appreciate it.