Latest / The Refrigeration Mentor Podcast / Episode 331. Compressor Electrical Failures

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Episode 331. Compressor Electrical Failures · The Refrigeration Mentor Podcast

• 0:00
  Speaker: What's up everyone? Trevor from Refrigeration Mentor. Super glad that you're here. Been doing tons and tons of training with some great technicians from all over the world. This is, it's so fun doing this stuff. So seeing the technicians grow fast, track their knowledge, just leveling themselves up. And it's, it's cool to see that it, it is cool to see people wanting to take their careers to the next level and, and they're just, the courses are just feeling up.
• 0:01
  Get to that next level in commercial refrigeration, supermarket, refrigeration, CO2 refrigeration. Today I want to dive into some compressor electrical failures. I, I think this. Something that is, that is super important that you can actually go take action on. That's what I wanna start doing in the podcast is hopefully being helping you go out there and actually take action, look for stuff, help build your repertoire of knowledge, really build up some skills in with compressors.
• 0:02
  The texts just say like I just needed to change it. I changed it. I did the, the basic checks, but then the compressor failed a few days later and like we're talking like six cylinder compressors sometimes. And I know I've seen this happen and happen to me, but one of the big things is, is that we got to find that root cause.
• 0:03
  That's what I, I want, I got got a list of stuff that I want to go through and see if this, this'll help you. Okay. One of the first things you can have burnt motor whining. So this one's not, not too difficult, but really what happens is the compressor trips on its overload. You smell like a strong burnt smell, , or a high amp draw before the failure.
• 0:04
  You can check right down to the, from the phases, cross each phase and then to ground, and you make sure that ground is a clean ground. Another one could be a short to ground, so this would trip the the breaker immediately, right? So all of a sudden turn the system on. Boom. Trips. So what you wanna do there is you're gonna wanna do a mega test on these ones.
• 0:05
  But when when I checked it with the high pot test, it failed. And so when I put it on the machine to start the compressor, it just tripped. It went on. It tripped the. It tripped right away. So I knew that the windings were faulty, but my standard meter didn't say they were bad. So this is the times you'll need to use a mega meter to test it.
• 0:06
  Okay. To make sure that you don't have it going to ground. And that's what we're checking for short to ground. One of the other things that can have it happen is oil contamination. So we, you go up and you see a compressor that has failed and you check with your meter and man, you got a short the ground.
• 0:07
  And what kind of contamination are we talking about? We're talking about turning that oil into an acid, bringing it back to its, its natural state. 'cause oils, most oils are made of water acid, neutralizers. For POE for an example. And so what happens when you have a ton of moisture in that oil, which because it's very hydroscopic, is that it starts to break down oil and it starts to cause turn into organic acids.
• 0:08
  And then that organic acid goes in and starts to degrade the insulation, which over time leads to that electrical failure. That is, that is one of the things that I like. I keep talking about, I got a, a compressor course coming up, an advanced service and compressor course. Check that out. This is what we dive in deeper in, in it and show pictures of it and understanding pulling a deep vacuum is so, so important because that oil contamination could cause a short to to the ground. And another one could be is single phasing. Like a si single phasing could have a, a loud humming. The motor overheating really this is something you want to want to check.
• 0:09
  , You check, okay, I got 75 amps, I got 75 amps and I got 75 amps. And all of a sudden one leg that was, that was needs to be pulling 75 amps. It's not there. What does happen to those other two legs? ' cause that motor still needs to pull that. Pull that voltage, it still needs that energy to turn that whining.
• 0:10
  So that's why you get some loud humming if it doesn't start. Another one is phase in balance. Okay, well really what is a phase in balance? We gotta think about this. Well, phase in balance really is uneven amp draw between the different phasing. , This will cause some sort of nuisance trips, overheating.
• 0:11
  This could be causing phase and bounds. This is why we have phase protectors on a lot of systems, especially larger systems. We have phase protectors racks. You see them all the time. Motor savers, IC then if you have a, a voltage I balance more than, and two, 3% there's an issue, and I know you'll see on some are up to 5% 8%, but if you got more than two or 3%, say it's a two 30 volt motor.
• 0:12
  Oh, I didn't get this. You gotta fill that information out. That's, that's how you get better, is looking at the data. Looking at the data. So, so important. Another electrical issue could be locked rotor. Well, what's rock locked rotor? What really happens? Well, you breaker trips instantly on startup. So really, your compressors don't even turn on.
• 0:13
  'cause if it doesn't spin freely, that's, well, that's a locked, locked rotor scenario. Now can you get it unstuck? Well, maybe. So if it's a semi-hermetic compressor and even scrolls, I've seen it, you switch the legs up for a three phase anyway and see if it's spins. The other way. So for semi hermetics, doesn't really matter if you switch the phase because they, the pumps will pump either way.
• 0:14
  'cause if you got oil in there, you're, you're not gonna seize. 'cause you got the lubrication in there, you shouldn't seize at all. But what is causing that? So lack of lubrication, is it oil. Is it low oil or loss of oil? Is it flood back? Is it that washes the oil away, seizes it up? Is it a flood? It starts so you get a massive explosion.
• 0:15
  But it, even though you cut the power to the coil, your line voltage is still going through. So now you're just running. So what does that really mean? Now I'm pulling into a vacuum. Now I'm doing a high compression ratio. Now I'm overheating the compressor and you're just gonna burn up that compressor.
• 0:16
  And I've seen lots of the contactor fail. Another, another big thing is if you're replacing a compressor, if that compressor fails, change the contactor. Changed the lug nuts. I know my friend Steve Wagner from Copeland, he sent me some pictures a few years ago and the compressor left the factory. 'cause the way Copeland does it, they tag it the serial numbers by the date it leaves, it gets off the line.
• 0:17
  I don't know if it was the same contractor or a different contractor, I'm assuming it was a different contractor. 'cause the person that's sent in the second one when I see the shirt, they just cut those wi wires right off, left the lugs, right onto the compressor. And then you could see that, that there was one of the, the lugs that were not good, the electrical.
• 0:18
  The big thing is, is that what we need to do is we need to check. Is the right amount of refrigerant coming back, cooling those windings. Is the condenser plugged or not plugged? What is causing that compressor to re is the voltage good? Do you have a loose wire? There's so many different things that.
• 0:19
  Internal protector, an overload device. So you want to check, check that. Always, always check the run A rated load amps. RLA is rated load amps for compressors and on the side of the compressor it's gonna have rated load amps depending on the manufacturers, but you're gonna have the rated load amps on there.
• 0:20
  And depending on the, the design conditions will depend on. Where it should be at, what your amp should be, but that top amp rate, the rated load amps is high, the highest condensing and the highest suction that compressor can handle, and it's actually above that. So you gotta go into the Bitzer specs or the Bitzer software.
• 0:21
  You gotta see what is the ambient outside? Is it real? Is the ambient really hot, high outside? What is did you get your meter out? What is the voltage? So. So, so important to check those things and it, it's quick checks. I was doing another training duration training recently, and we, I was asking the questions about, , if you got a high sub cooling and high, the high sub readed and high discharge pressure and high discharge temperature and high s, well, what does that really mean?
• 0:22
  Just on, on that there, am I getting the right voltage? Am I getting the right ams? You do have to get the, to really plot an efficiency curve on a compressor or plot like the compressor efficiency. What you need is your suction pressure, suction temperature, volts, amps and that's a perfect starting point.
• 0:23
  And how do you get a short? Well, it could be some dirt that gets in there and what else, what else could happen? So the. Lead breaks off inside the compressor. I guess the other one that I just talked about, that would be more of a short, so if you get like dirt inside it and it causes a little arc inside there, that's more of a short, so not an open winding.
• 0:24
  And so they could be broke off or burnt off. They can be fixed. , That's what manufacturer manufactured when they remanufactured a compressor. They're fixing stuff like that sometimes. And it does happen. It does happen. Vibration could do it too. If the system's vibrating the whole time, they, and they, someone changed 'em that terminal plight or terminal.
• 0:25
  If they're bulging, the oil leaks at 'em, they got burn marks, you gotta replace them. You always replace 'em with the correct micro fared and voltage rating if you can. The big thing is, is any single phase compressor that fails, change those stark components. Change them every time. Every, every, every time.
• 0:26
  Go back to manufacturers single phase because just that wasn't checked. Okay. Also could have voltage drop under load, like those compressor starts because the struggles to start because you'd have the voltage drop, so you wanna make sure that you're not getting any voltage drop. Is there too much load on on the, the.
• 0:27
  Miswiring is another electrical issue. So if it's incorrectly wired, this happens on single phase compressor. So, so much. I've seen it in the past. So you gotta verify that those like the T one, T two, T three terminals and make sure that they're matching the wiring diagram and the start and the run leads and the ground leads are properly placed.
• 0:28
  So you don't, definitely don't wanna run it backwards for too long. So check that reverse phase. I think, yeah, any faulty starting components is another major electrical issue. I talked about the start and run cap, but there's also a start relay. Or a PTC device, really the potential relay that works off back EMF.
• 0:29
  So lightning strikes, switchgear issues, bad power grid. , You wanna look for arc marks and or insulation breakdown. You might want to do mega meter tests and the windings to see if there's a reduced in the installation we talked about already. That could happen for sure. Another, I think I might have talked about this one already.
• 0:30
  It scratches through the, that insulation in there and all of a sudden, bam, you get a short phase to phase where you can have a issue, where you get a short, a turn to turn short. What does that really mean? That means that you're, you gotta short between phase one and the wires going through phase one. So if you ever looked in a a wound motor.
• 0:31
  You can also have shorter coils that cause damage. The contactor for an example, or winding ground grounding. That that could grounding too. So inside compressor, so you have the stator and then you have the rotor. So the stator has like different slots on it and different la la they laminated it, iron cos I think that's what they might be called.
• 0:32
  There's so many, so many electrical things that, that can cause the compressor to fail. And I think it's important, to understand the electrical failures. What cause the electrical failures 'cause that next compressor, if you don't understand and you don't fix the first problem's gonna fail again.
• 0:33
  So write out your checklist when you're going to do a service call on a compressor or on a system, a condensing unit. Do write out what the checks that you would check, and I think you're gonna be surprised that there's a lot more checks than you do because it's it when I, I do so many trainings. I talk, I've talked about, let's talk about the checkpoints you did and what was the issue.
• 0:34
  So you're gonna be able to look at trend grasp better. You're gonna be able to look at, and this is how you help more people. This is how you help troubleshoot. 'cause when someone says, okay, well I got real high amps I have real high condensing pressure. So I got high, high head pressure. I have a full sight glass.
• 0:35
  I hope you took a few things away. I hope that you go out and you try some of the, check some of these stuff. Get your meter out and start using your meter a lot more. It's gonna make you better. We do have courses all the time. Head the refrigeration mentor.com and check them out. Check the hub out, check the YouTube channel out.