Hi everyone and thanks in advance for your replies. I have been doing hvac and refrigeration for many years, and this one has got me.
This all started last week, I have a 6 door freezer with 2 evaps and they share a common condenser. Everything is hussman, very old hussman. Anyway, I got the call last Friday, that the case had got to about 40 degrees on thursday. When I arrived, the case temperature was at 15 and all was well, so I began to dig deeper. When I walked up to the condenser, the compressor and all fans were running, I went ahead and turned the timeclock to initiate a pumpdown, the pumpdown took a very long time, but it finally did shut off, so I energized the solonoid, and it opened, and then the compressor sat there and hummed pulling locked rotor amps. At this point, I shut off power, reversed 2 legs of power (3 phase) and it took off and ran. This time I decided to do a pumpdown test, and this verified that the compressor would not pull into a vacuum, and the compressor has a loud rattle. Pressures were about 270/24 on 404a. shut off compressor, and it wouldnt start again. reversed legs, still would'nt start. Verified that I was not single phased, or that voltage was ok.. Here is the deal. I had and have 198 volts give or take 2 between all 3 legs. Pulling close to lock rotor amps. Comp nameplate says 208/230. As a final test, I used my gauges to equalize pressure on the compressor. Still won't start. So today we replaced the compressor. Now, the compressor will run and runs fine, amps are a tad high due to the low voltage I am dealing with, but two times I just hit the oil safety test switch, and it will shut off the compressor for a split second and it wont come right back on when I release the button. If I hold the button in for 2 or 3 seconds then release it, it starts without a problem. I have never had starting torque issues with a 3 phase compressor, and I have seen these things run all day long on 195 volts, which is well within 10% of 208. Here is the other question I have, I talked to my local copeland rep, and he said that these compressors don't like to start with the pressures equalized, and to me (and anyone else I have talked to) doesn't make any sense. Is the problem fixed? yes. Am I a little concerned? yes. So, if any of you have any answers, I would be more than willing to listen. I also changed the oil pressure safety and contactor. And the compressor starts fine coming out of a pumpdown. ?????????