Refrigeration Compressors?
Loud Bang? Blue Lightening?
Refrigeration compressors not running? Did you check the condensing unit breaker? Find it tripped?
Is the unit using high voltage? Maybe it's 480 volts, three phase equipment?
Before you reset anything do your heart a favor, first check for grounded motor windings. High voltage refrigeration equipment does scary things when grounded!
Once while working late at night on top of a cooler, I reset the breaker on a grounded unit. The loud explosion and blue lightening streaks of electricity sent my helper off the roof!!!
No, I learned the hard way. First try to isolate what tripped the breaker. I always start with the compressor.
What procedure do I follow?
Placing my meter on the meg-ohm setting, I scratch the cabinet surface with one test lead. This assures I have good contact, especially if the cabinet is rusty or dirty.
I double check this contact by also placing the other lead on the cabinet.
The meter should register around zero ohms. I'm ready to begin testing.
Using the lead that I tested with, I apply it to one compressor wire, keeping the other test lead on the cabinet. What should the ohm meter read?
If the winding is OK, it will read very high resistance. A range of 6 to 8 meg-ohms or greater.
But, a reading of a few hundred to a few thousand ohms? NOT GOOD!!! I have a grounded motor winding!!!
One, two, or all three, if any or all of the compressor wires are grounded, game over!!! The compressor is dead!!!
Or is it???
Did you notice I tested the refrigeration compressor wires?
It's the lazy man's way!!! It's great to begin at the starter or contactor. The wires are right in front of you.
But if you read a ground, don't stop there!!! You have to get the final readings from the compressor terminals!!!
I remember condemning a compressor only to find no ground when I checked the terminals. What the heck!!! Where was the ground I read at the starter?
You guessed it!!! One of the wires between the starter and the compressor had rubbed through it's insulation. The ground was the wire touching the conduit, not the compressor.
I replaced the wire and fired up the unit!!!
Was I disappointed??? After all a damaged wire is a lot less money in my pocket than a grounded refrigeration compressor!!!
NO WAY!!! I relish the opportunity to prove my honesty and integrity.
Your customer never forgets!!!
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