A compressor that is shorted to ground or grounded can be a costly issue for clients and can also be a really big problem if a technician diagnoses. In this video, we'll take away all the guesswork and dive into how to diagnose this correctly using isolation diagnosis, as well as more about tripping breakers.
First, when you find a tripped breaker, it may be tempting to just reset the breaker and see what happens, but don't do it. Remember, a circuit breaker is designed to open the circuit during a high-current event. This will happen very quickly in the case of a shorted or grounded condition, and it will happen more slowly.
When there is a less extreme overcurrent condition during operation, every time you reset that breaker, you risk creating a major arc or spark.
If the short is inside the compressor, you're just adding carbon and acid to the refrigerant, further contaminating the system. So the first thing we need to do is a thorough visual inspection of all the high-voltage wires, terminals, contactors, capacitors, cranks, cases, and the breaker itself.
Disconnect, check for any signs of abrasion or damage, and check for any loose connections or signs of arcing. If anything looks black and damaged, that's where you need to start next.
Once that's done and any issues corrected, inspect the compressor leads and terminals themselves right at the compressor, but remember safety first.
Make sure to wear gloves and safety glasses, especially because those compressor or fusite terminals may be weakened and can pop out, resulting in terminal venting of the internal refrigerant in a dangerous condition.
Next, take a photo of all the wires or tag them before pulling them off the terminals. This will help avoid any miswiring upon reassembly. measure resistance to ground from each terminal.
Usually, you're going to do this from the terminal to the suction or discharge line on the compressor. You can use a mega-ohm meter or other quality multimeter
Keep in mind that some compressors are still considered good all the way down to 5 megaohms from the terminals to the ground. This 5 megaohms number comes from Chrysler, especially for scroll compressors.
As the windings are immersed in refrigerant and potentially oil, you may read a high ohm resistance to ground and still have a shorted or grounded compressor because that shorted or grounded condition shows up once high voltage is applied.
Keep in mind that the quality of the reading will depend on the quality of the meter used and the resting state of the motor. When you're convinced that the compressor is shorted to ground orgrounded, it's time to isolate the compressor tape and strap up the plug or terminals, ensuring they aren't touching anything, then reassemble the unit and reset the breaker.
If it doesn't trip and everything else, like the condenser fan motor, runs properly, then you've correctly diagnosed the issue as a shorted or grounded compressor.
If the breaker trips again, it's back to the drawing board.
You need to test the other components, but at least now you have a step-by-step approach to diagnosing a grounded compressor.Remember, accurate diagnosis saves time and money for your clients, and performing a visual inspection followed by an OM-to-ground test followed by an isolation diagnosis before condemning a compressor is shorted or grounded is a best practice.Thanks for watching. If you're willing to give this video a thumbs up and drop us a comment, don't forget to hit that bell icon to stay updated with all of our future videos.
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