Bryan covers the most common newbie mistakes when diagnosing compressors.
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Read all the tech tips, take the quizzes
and find our handy calculators at https://www.hvacrschool.com/
Driving home make sure this driving home, I'm gon na talk about first off, first off first off when I do these driving home videos, somebody gon na be like you're distracted driver. Don't do that! I'm not looking at the camera! Okay, just driving and I'm talking so chill hands-free I'll look into the phone screen doesn't even scream for me to look at all right. So there's my displaying from don't do this at home. If your looking like it's cell phone screen or something like that very gon na distract it, so what I want to talk about today is three things that new technicians really screw up, often and a lot of times is innocently when they're trying to diagnose a compressor And then end up with them saying that a compressor is bad.
What is it's not bad and the first one is really simple when it comes down to doing a proper visual inspection. I've seen technicians, diagnose a shorted compressor because it was tripping the breaker and they never actually went to the terminals. So whenever you're checking for a short on a compressor, you have to check it at the terminals themselves. So pull the terminals off pull the wires off and you check it at the terminals.
Don't do it at the contactor up the top of the leads, because you could have leads and to come apart or corroded or shorted or whatever it's a really dumb one. Not a mistake, I've ever made. I have made the mistake, I'm really early on when I was probably 19 or so I made the mistake of telling somebody, because their terminal was damaged, that I can actually get a spade on it that they had to replace it. And then somebody went back in with the terminal, repair kit and replaced it made me look stupid, always best to give the customer all their options.
Let them decide what they want to do, what they value, return or repair kid. On my truck yeah terminal burns off a lot of times, they can be an indication of another problem, but a lot of times. It just means it's a loose terminal, so one is misdiagnosed compressors because they didn't visually inspect at the terminals. It's always been.
The side. Note he's about four stupid, sorry about that. My mother bought them for me, okay and I happen to have them here in the van that's bright, Lord, I'm not trying to look cool mistake. Number two: is they don't let the compressor cool off before condemning, and so when a compressor goes in a thermal overload, especially when it goes in a thermal overload because of a running condition.
That's caused it to be very hot, like physically the entire shell hot there's. A difference between he and the windings that occurs like we have a bad capacitor or something like that, and it goes out really quick because a blocked compressor. It was cool off really quick, because all of the heat is isolated in the windings themselves. The windings become heaters and the thermal overload is inside the windings.
It's cuts off really quick, but when a compressor is running hot and this especially happens when it's low on charge or what has a serious restriction or something like that, where it's not you know, the result is really low, suction pressure and so that's low mass flow Rate and high superheat and that causes compressors to overheat. So, there's a lot of reasons that cause compressors over here: you're not going to go into all those. That's a different video, but when a compressor overheats because of a running condition, it can go out on a thermal overload and stay out on thermal overload. For a really long time - and so some people will use a hose hose, can help speed up the process. I've pulled off a lot of compressors with the hose, but recognize that with a big compressor, especially, you have a lot of thermal mass there, and so sometimes it takes a while for that thing to reset. So, just because you can't get that thermal overload, the reset, which is an open condition between prominent start comment and run --, and but you still see a path with your own meter between start and run and the compressor won't run. That's an indication of an open thermal overload. You got to give it some time, don't be too quick, because you're gon na end up Demming the compressors and somebody else is gon na go back out.
Once the thermal overload resets throw the disc Ike it's going to come on and they're gon na think that you're trying to escape and again this is something that I think, a lot of technicians misdiagnosed, just because they're in a hurry, and they don't think that that They can be that difficult. I'm one trick that I've learned on older compressors if they're kind of on our last leg anyway - and you know that it's cool I'm sometimes you can kind of bump it a little bit and that'll help. That level overload reset a little here, sometimes again, some of you know ers, probably like bump the compressor, but again an older compressor, sometimes to get that thing to reset just a little bit of bumping it around maybe grab the sectionalize shake it a little bit than That especially an old reciprocating compressors where they are on suspension and so shaking it around up, get it rigged. The final thing that technicians off and get wrong is they think that you can home terminal determine, can old terminal charcoal, that's helpful.
If I don't open the lining of the thermal overload but finding explored by oming terminal, the terminal is really tough, because a lot of compressors have lowers this terminal. The terminal. Anyway, you can't work Ohm's law just with an ohm meter roaming at a compressor and then figuring out what the amperage is gon na. Be that's not how that works, because it's an inductive load and so the bulk of the resistance and a compressor is what we call inductive reactance and so the total impedance, which is total resistance, resistance and inductive reactance kind of mixed together.
That's what you care about! That's what results in the amperage of a compressor, but you can't just have a compressor out and figure out what the amperage of it's gon na be and the school you think it's gon na be cool! You just home it out! You're like oh! This is way lower than it should be: the compressors bad you home a compressor to ground and then, as a final test, to isolate the compressor and then isolate the terminal. So two compressors disconnected you reset the breaker, the breaker resets, with the compressor isolated. Then you know that it's the compressor, that's kind of your final test, but don't go condemning compressors, because your oming leg, the leg and reading low ohms and definitely don't use a mega ohm meter, especially like the stucco. Whatever the thing is and home leg the leg, because of course it's gon na read back because, like the leg is very low, ohms, that's a natural that it would be, and a lot of guys will say well, it should be. You know they say common to start and common to run should equal start to run yeah. That's just how the motor is wired and that's it's just pretty much always going to be the case unless it's make sure to the mass that you're gon na see it for cram. So when you're checking for us a grounded condition to ground and then you're using that isolation test, that's final kind of your final verification that it is to compress a lot of compressors get misdiagnosed, because guys will do that. Another thing is a lot of scroll.
Compressors get mixed diagnose, especially as bad using that stuff go mega, ohm meter because even Copeland says that point 5 mega ohms anything lower than that they'll say that it's bad to ground, but that meter shows at 20 mega ohms it'll start showing it failed. So you could have a good score score compressor! That's fine that that meter is showing as bad now for recent open motors yeah, okay, fine, 20 mega ohms is kind of the drop dead point and, and generally speaking, you know, 20 mega ohms is pretty close to ground. I know I'm getting a little bit on the edges of this here. The third mistake that newbie techs make is that they measure leg to leg and they think that they can find a leg to leg short and that's it's possible for you to.
But you would have to know what it was supposed to be in the first place, and most of you don't know that so number one visual inspect the terminals check at the terminals themselves, rather than back up at the contact, isolate a compressor. To give it more time for thermal overload, don't get impatient; 3, don't bone the leg to leg and use that as the only factor for condemning the compressor do that isolation test just tripping the breaker, isolate it reset the breaker resets. At that point, then, okay, those are your three things: presser diagnoses, biggest mistakes, I see newbies and then compressors floor.
Your highly skilled cool kind guy buddy
AC guy checked mine wrong and said mine was shorted. 125 bucks for the wrong diagnosis. They wanted 2 1/2 times the cost to install a new one. Luckily I called a retired AC friend and he said you have to pull the wires Off. Turned out the hard start relay was shorted. Removed it and it fired right up. Never figured out why it had a hard start on it. Service area Barrhaven??
Can we rebuild hermetic ac compressor…if yes .Can I have your contacts please Are you in Barrhaven ?
I hate to be rude maybe you sound like he was just babbling I couldnโt hardly pick up on anything youโre trying to explain
Loved how you added the tip about bumping the compressor if the overload doesn't reset. I've had compressors before where the overload never reset. Even well over 24 hours of letting it cool off. Gave it a tap with a rubber mallet and then it did haha. That simple tip saves people money!
Fresh out of a trade school program. Will tattoos effect the ability of me to get a technician position in a company Service area Nepean??
I had a difficult compressor today. Ohmed out good leg to leg, no short, no open but refused to start. It's not tripping the breaker either. I put a 3 wire hard start and it clicks out after 3 seconds. I ended up replacing it but it was difficult to condemn it. Of course I checked the cap and even replaced it hoping it would start.
Thank you so much for your videos! I am currently in school to get my license and after I read every unit I then watch your video on the same. It really helps me retain what I am learning!
Why this guy doing domestic HVAC instead of commercial HVAC, refrigeration or industrial refrigeration…
Had a overtime call thermal open condenser fan seized come back next day customer can't wait ok go out get 4 bags ice i'll start doing the motor .
Part of the reason talking on a cellphone while driving is so dangerous is because our brains are physically incapable of giving 100% of our attention to more than one task. This means when you are driving and talking on the phone, you are splitting your attention between at least two activitiesโdriving and talking.
You are not in control of your vehicle when you take both hands off the steering wheel to gesture.
Hvac school. What if you have 2 open windings on 1ph 175v conpressor (residential fridge) lg compressor. I know if it overheats 1 winding opens. But you have 2 windings with no resistance /continuity.! Diagnosed bad compressor. I thought common sense. Turns out the new compressor comes in with also 2 open windings! Wth!
Brian looks like 4โ5โ๐ ๐๐
So if we can not use the supco Megaometer for the simple reason ! Why not address this issue to Supco!?
Good stuff. This is the right and proper way to diagnose the scroll and recip compressor when a tripped breaker call is received. The first year Super Techs will be compressor masters at diagnosing compressors correctly.
How about running a water hose over the top of the compressor like I normally do and waiting for the old meter to start beeping
Compressor Hard start with relay can also save the compressor if not short to ground & make you look like a hero. That client will call you to replace the whole system .
I used to believe if you read anything but OPEN LEAD (OL) to ground that the compressor was shorted to ground.Turns out that a little voltage will always leak out of the windings and find its way to the shell casing via the refrigerant and oil.
"Heat in the windings" shows picture of scroll. SMH.
This video is very concise. You kind a got to the point and got your information out! Maybe you should do more while driving LOL
Had the exact oposite problem one winter the compressor oil was too cold to circulate and it wouldn't run. After the sun come up and warmed it enough it allow it to start up. Service area Kanata??
Learn how to use a MEGGAR! I mean a real one, not a cheap, battery powered one. Use a self powered hand crank meggar, like AEMC 1250. Learn how to interpret the readings, and use it as a part of your preventive maintenance program, to evaluate the condition of the oil/refrigerant atmosphere that the motor windings are being exposed to.
Resetting the breaker after isolating compressor is a great tip. Us rookies need all the help we can get. Thanks
You talk tooooo fassst
Been using the supco for over 9 years has always matched my meter..don't agree brother
Keep a couple of ice bags in side your cooler not for beer but to cool off compressor no hose needed plus works faster just put them in top.
Your mommy bought you those glasses? Ahhhhhh
And dont forget to try hard start kit on older compressors u can squeeze 10 more yrs out of some
Over 30 years in this trade and I just now find out using a defibrillator, yelling at the homeowner to clear, emotionally shouting at the compressor to stay with me, before saying he's dead Jim is not the best method?
Whats next, saying checking for gas leaks with an open flame is a bad rookie idea.
But seriously, back in the 90's I misdiagnosed a compressor, thermal cutout was the problem, second opinion tech from other company figured out the real problem, homeowners thought I was out to gouge them, but it was a rookie error.
My senior tech has always said insulation testers were no good, he doesnt use them, and hes been in the field for 40 years!
Love the videos, keep em coming.
yesterday, i had a unit with a burnt off terminal. today i had a unit that was out on thermal. both fairly common problems. i have a semi-hermatic on a walk in cooler, that is just about gone. its got high consumption but still might run. how do i tell if its good enough to use? Are you in Orleans ?
You can ohm a winding. It will read infinity 0
If you have thermal overload a lot of times is caused by those damn thick blankets on older units especially the shitty Trane/A.S ones and the B.O.P compressors which are the purest junk there is!!
I (ALWAYS) remove the shitty blankets on ones older than 10yr that is experiencing any issues… I know what is coming and try to save the homeowner time and calls for the future.
"CONTINUITY TESTS" for continuity to ground going leg to leg comes first, then continuity to each other to rule out broken winding or overload, then ohm each leg and add up.
Use a water hose on compressor if thermal overload or no "continuity" to "common" is found, leave meter on so you know right when continuity comes back… That is the quickest way to cool one down… Had one tonight due to the thermostat failing to send "O" signal to RV causing heat mode in 88* weather ambient, kicked the compressor into overload with blanket. 20yr old unit so i removed blanket, and before hose could be got it cooled down, started back up to find issue, tied the o and y terminals together for temp fix until homeowner could get thermostat due to him being "broke" as he claimed.
Temp fix can go a long way!
Wish I could be a assistant tech for you Service area Orleans??
Great job
This is very informative for some new guys. I have also seen misdiagnosis on a compressor with the reversing valve stuck in mid position. This could have many unseasoned techs think there is a problem with the valves in the compressor. I almost misdiagnosed a compressor once cause my gauges were open ( yeah that happened) But I caught myself before I made myself look like a dummy.
What about continuity on legs of compressor terminals grounded to copper lines.
Stop talking with your hands!!!
What if the compresser doesnt pump down is it bad
Lol the glasses comment ..lol….
How do u keep ur van quiet Are you in Kanata ?
When I first got into service work I had a Carrier 40 ton packaged unit that was tripping the first stage compressor. Checked the terminals for a short. Found none. Still tripping the overload switch. Found out carbon around the strips around the terminal was the problem.
Biggest mistake youโve made is having that Carrier emblem on your shirt๐, ouch and those testo gauges, all jokes aside, good video Are you in Ottawa ?
Pfff, Gently shake the compressor? I go at it with a "gentle" wallop right on it's head with a dead-blow hammer..
Just don't ohm out the compressor terminals if you've got your face right in front of them and there's refrigerant/pressure in there. It could blow out the terminals right in your face. Never seen it.. but I've heard it happens
Awesome video! Liking you van chats ๐
Every single time I watch HVAC School vids or listen to the podcasts I learn a little something. Thanks for taking the time to make them!