Critical System Diagnosis for Residential HVAC

what it comes down to is i'm seeing more misdiagnosis and their misdiagnosis not because it was like a really complicated problem but because like we weren't even really in the ballpark and when we make a diagnosis where we're not really in the ballpark that means that we're guessing that means that you're getting frustrated and you're just saying um yeah it's probably the compressor bet it's probably the board but it's probably leaking the coil whatever the case may be right and that's a really really bad trade it's not something you want to engage you want to you want to start going down that path because it leads to it leads to bad things because the reason why you start to do it is because you do it a few times and you get away with it and it's just like i don't want to know the story with this compressor i'm hearing you guys grumbling about this whatever um but just like with what's going on here there seems to be some lack of clarity about what happened here and that is not an acceptable way to run a service business like it's just not it's not okay it's not ah well maybe uh you know well okay crap happens that's not the sort of mindset that we need to have towards diagnosis okay and that is a little bit of a kalos thing that's starting to creep in which is just sort of like well there's so much expected of us you know you're just going to make bad diagnosis sometimes and that's just how it is and that's not how you think about that any more than you think that way about failing an inspection do you with the failing inspection you don't have the mindset of uh well you know an inconvenience is the customer we have to go back another day uh you know whatever that's not that's not how you think about that right i'm not how you should and the same thing is true with diagnosis so we're not always going to get it right and we're not always going to pass every inspection okay so that's that's a given but if you're this reason why we didn't get it right or we didn't pass the inspection then you shouldn't be comfortable with that in yourself and i don't care if you don't if it's not a kalos thing think of it as a personal development thing if you get the mindset of being okay with letting things go that are incorrect then that's going to follow you and 10 years down the road you're going to be one of these grouchy old technicians who says oh i just pushed them above my whole life and i don't know why i'm all i'll never get any opportunities you know you hear this all the time um from people who don't hold themselves to a high standard so don't make this about me don't make this about comparing yourself to somebody else because that's a and now caleb there's some pretty good people to compare yourself to there are some really great uh people here but even that don't compare yourself to another person because then you're always gonna have an excuse as well like for example if i run a service call and i forget to quote a drain line or fail to quote a drain line where it should have been quoted and i get a call back that was my mistake i should own it but that's not an excuse for somebody else to get a call back that may have that scenario may have exactly happened you get the point so what should happen is you should tell me hey why didn't you put that drain line and i should say what what should my response be when i didn't quote the drain line and it results in a callback it should be yeah i should have i should have quoted that good catch thank you for telling me right because there's something to learn there it's not oh yeah well that one install you did or whatever whatever comeback that we want to have and there is a little bit of that it's a societal thing but it's also a theme that i'm seeing grow in caleb's culture which is rather than just saying it doesn't matter if somebody else isn't doing what they're supposed to do i need to do what i'm supposed to do so from terms of diagnosis you have to care about getting the diagnosis right not necessarily about at the end of the day i mean you know it's more important at the end of the day the customer has air conditioning obviously but you can do be a really bad diagnostician and get the customer air conditioning at the end of the day you can just keep you know loading the parts cannon and firing parts at the unit you know until it starts working and that's not how we do diagnosis so i'm going to talk about some key areas that when you run into these situations i want you to pause i want you to think a little bit more about what you're doing before you move on and one of the first and biggest is the compressor so what we're wanting to prevent is the cop-out attitude the attitude of well i got to get onto the next call somebody's pushing me um that's a cop-out attitude to to not make a good diagnosis and then also the unwillingness to take feedback attitude it doesn't matter how much you don't want to hear feedback from a particular person it doesn't matter if you don't respect them you know because this happens sometimes in work that you may work with people you don't totally respect if what they're telling you is correct then you need to hear it and you need to learn from it that's just how it is it doesn't matter if you like them personally it doesn't matter if you you know hang out on the weekends it matters if what they're telling you is something you can learn from everybody agree with that concept that's a good general concept we can all live that way right all right me everybody all right so let's talk about compressors here let's start with um there's really there's really three primary uh types of compressor failure what happens when a compressor is open anybody know let's start here do we have an open circuit between these two probes right now yes now do we have an open circuit between these two probes no now we have a closed circuit right open circuit closed circuit what do we call a closed circuit that is an undesigned closed circuit meaning that you're you're making a circuit that's not supposed to be there we call that a short right and it's a very simple why we call it a short because it's taking an undesigned path it's taking a path that you're not expecting or that you you know hadn't hoped it would take right it's a short it's it's it's not taking the long way it's taking a short way got that all right so that first category that you both uh mentioned a burnout and insulation compromise that is a short circuit and the most common short circuit by far is what we call a short to ground or a grounded compressor okay now why do compressors ground rub outs and overheating yeah so internally yeah so overheating can cause it um or loss of oil can cause it lots of lubrication can cause it those are two of the biggest reasons why that occurs and so inside this compressor you've got a motor and you've got a pump basically a compressor is a form of a pump it moves refrigerant around right and in this compressor particularly you also have suspension so this whole compressor is suspended inside of this shell and so when refrigerant comes down this suction line into the compressor suction line in discharge line out comes in vapor it literally just dumps into this shell if you were to look on the other side of this suction line what you would see is just an opening it just dumps into the shell and then the compressor pumps out of the shell out of the discharge line okay follow that so if something happens inside this compressor where maybe the suspension breaks you know you heard those springs that the compressor's sitting on say that suspension brakes what's going to happen inside that compressor just from a practical standpoint start banging all over the place right and what will happen eventually after it's banged around long enough the windings will become compromised right you're going to damage the windings and once you damage the windings those windings can either short to the shell or they can short to one another and regardless what is that going to lead to that's going to lead to an undesigned path of lower resistance than it was designed to have okay lower resistance equals higher amperage or higher current a short circuit results in primarily trip breaker balloon fuse that's what we see most often right so you walk up to a job triple breaker blown fuse now is a shortage compressor the only thing that can cause a trip breaker or a blown fuse now lots of other things can cause it crankcase heater that's shorted out it could be a breaker that's that's you know that's failed could be could be a rubbed out wire it could be a what's that loose connection could be could be a loose connection in some cases sure bad contact could be bad contact or we found that yeah that was a weird one really weird one actually there's lots of things that can cause it so at the end of the day if you look we're going to jump straight to the conclusion here i'm going to jump straight to the punch line end of the day you think this compressor is shorted what is the very last thing you need to do aaron you you go to a job on a weekend and you think you are darn sure the compressor is shorted breaker is tripping so you think it was shorted and you're about ready to write it up you're about ready to put it into the parts channel so we quote a new compressor what is the very last thing you need to do before you walk away from that job isolated you need to isolate it take the leads off of the compressor see if everything turns on it doesn't trip exactly tape those leads up really well not to each other separately take those leads up really well so they're independently isolated put everything back together and reset that breaker should the breaker reset yes because you're saying that the compressor is shorted and if the compressor is shorted if the compressor is isolated then the unit should power up now of course the compressor is not going to run obviously because it's isolated but everything else should run the fan motor should run contactors should pull in everything else should be fine right does that make sense this isn't a suggestion this isn't like a quick tip for living well this is every time you diagnose a shortage compressor you do that as your final step every single time now you may add that might say your final step your final diagnostic step the next step if you know you're going to do the compressor i i would suggest that we go ahead and weigh the charge out right now why would we weigh the charge out right now before we even go to get the compressor or do anything else see if it's low or if it's overcharged because if it's lower overcharged either one of those can result in a failed compressor and you kind of want to know that because if it was overcharged maybe somebody was compensating for low airflow maybe it has a bad valve right if it's undercharged maybe we have a leaking evaporator coil or a leak somewhere else now you know that before you walk away from that job and then you put the new compressor in the customer you fire it up and then find out that it's you know it's not working that's a that's a pretty uncomfortable conversation i would say so does that make sense everybody get that it's not hard to do it's your final step every time you will look like a genius right because you'll go up and you'll be like i'm sure it's a compressor you do all that and then bam it strips the record again oh then you start looking again oh man the crank case heater this is a train compressor so i don't know if you guys have ever seen this but there's a well down at the bottom of this compressor that an insertion rod cal rod style crankcase heater goes into these suckers are known for breaking apart and shorting out to run to an older train compressor that's something that definitely happens quite often another thing the other reason why i want you doing it this way is that it forces you to actually look at the terminal nothing makes me crazier than somebody who diagnoses the shortage compressor and they didn't actually even pull the top off to see the terminals to make sure that there's not a short at the terminals themselves you guys all get that so that's mostly what i wanted to say about a shorter compressor now let's move into the the diagnostic part quickly i'm not going to go into the different ohm readings on the compressor um though in the video we'll flash up the little you know common home readings that you see because really as far as the standard home readings people will say things like start and run is uh equal to start plus common uh or sorry a start and command and run and common put together well that's a fairly obvious statement that's not really a diagnostic test like i don't really know why people do that it's not really a helpful diagnostic test what you're primarily looking for when you're looking for a shortage compressor is you're going from the terminal with the terminal isolated to the copper on the compressor a nice solid scratched out spot on your discharge line where you're kind of making sure you're getting good contact and you're seeing do you have a path between these terminals and ground now like we mentioned before a short is any undesigned path of low resistance that causes high current right low resistance causes high current so it doesn't necessarily shorten the ground though that is the most common and when we say shorted to ground a lot of people in the trade freak out and say that's grounded grounded is its own thing grounded shorty to ground a short to ground whatever you want to say it's an undesigned path to ground it is a short it's a type of short but you could have a short where the windings themselves especially in a compressor that's in suspension like this where it's actually pretty far away from the shell but the windings themselves are just all melted together and that can also cause a short the problem is that short's very hard to find by measuring in between the terminals okay let's prevent a big mistake that a lot of you make you go from terminal to terminal with your own meter and you measure and you see a really low ohm reading if you see and by the way this one is showing open terminal terminal right now yeah so this this compressor is actually open who said that it was that it wasn't failed is this guy all right so terminal with terminal you should read in ohm reading but the problem is is that you think you know what that home reading should be and you don't that's the problem and so you say oh it's drawn five ohms it's drawing it's measuring five ohms i'm using weird language here it's measuring five ohms from start to run that seems low that seems high well there is no seams you don't know unless you know the specs for this compressor you don't know what home reading you should see now there are there ranges where of course you know it's too high it's reading the mega home scale for example you know where it's reading you know 0.1 ohms yeah okay at that point yes but even then your meters a lot of meters don't read well in the really low ohm range this is something that we've learned recently some meters will just go to zero even when it's point two or point three and some compressors will have point two point three point four ohms range between the run and common winding the lowest ohm winding here's the point omen from leg to leg like this helps you know whether or not you have an open like this compressor has so meaning that the windings are broken or the thermal overloads open so it helps you see that but getting a reading on this doesn't necessarily indicate to you uh that there's it doesn't really tell you much i guess unless you're very experienced with that particular compressor or unless you pull up the compressor spec sheet to see what the ohms are who here when diagnosing a compressor has pulled up the compressor spec seat to see what the ohms are in the process of diagnosis it's a pretty small number of technicians do that so unless you have done that and i definitely suggest it get the koblin mobile app look up the spec sheet from you know bristol or whoever your whoever the compressor is made by tyler this is the tyler compressor um and see what that is but unless you've done that you don't know what that should be so the point being that that that redneck test we call it where you do you isolate it and you reset the breaker that's actually a really good test because if it was tripping the breaker before then you isolate the compressor at the terminals and it stops tripping the breaker guess what's wrong with the compressor it's just that simple and from a weak breaker is that the thing uh okay it's a good question a week breaker so what does a week breaker mean what would that mean i don't know a 30 amp break for that trip at 17 amps sure that can absolutely happen but that's only going to do it during run like all all breakers that we use in air conditioning they have a they have a measure of time delay in them it's not like they're just going to trip like that just because of start amps that's not going to happen there's going to be now again i say it's not going to happen there's always the exception to the rule saying something has a weak breaker is kind of like when somebody says the system was leaking at the schraders it's like one of those sort of cop-out diagnosis or or i think somebody was stealing the refrigerant from the system and that's why it was low like there are these weird excuses that people use in order to just kind of get away from the job because they don't want to figure out what it is is it possible that there could be a weak breaker yes but you would only know that like over time after a series of unfortunate events and weird diagnosis that makes sense all right so in terms of testing the compressor the short is easy actually at the end of the day because you do that isolation test and that is a pass fail test at the end everybody get that okay open is also simple i just showed you you go between terminals and you see is it still reading ol and if it is it's open now if it's open in between this is always something to remember so you do common start run if it's open in between your comments your terminal is actually right here and there's a thermal overload in the circuit so if when you're measuring on your common terminal this is actually the common point inside the compressor where the windings connect so if you're measuring between common and run and you see an open or start in common and you see an open but when you measure between run and start you measure a path that's an indication that it's an open thermal overload your thermal overload is open and that's just because it's overheated and a lot of times when thermal overloads trip they take a long time to reset this is a common one where people say well hey i waited an hour i ran water on it for an hour and it still didn't reset yeah it may take three or four hours in some cases because again when that once that trips especially on a compressor like this with a big shell a big heavy steel shell there's a lot of thermal mass there and that compressor may take a while to reset so don't condemn that compressor until you've given it enough time to be sure that it's actually cool to touch if you touch that compressor and it's completely cold okay at that point and it still hasn't reset then you can go ahead and quote it but even then when you quote it you tell the customer this thing's out on thermal overload it could reset at any moment it's just not resetting for right now so you can wait it out if you want or we can go ahead and quote you a compressor that makes sense so thermal overload is a category of open compressor in the same way that a rounded compressor or a burnout compressor or a shorty compressor or compromised windings those are all terms for a short so you have short you have open meaning no path broken winding open thermal overload and then you have the next type of failure which is what grant grant grant what's the next what's the next category of compressor failure or locked oops i forgot i forgot uh locked compressor so there's actually four types i was just joking when i said three there's a there's a locked compressor and a locked compressor is what what does that mean for a compressor to be locked seized physically doesn't can't physically move inside so if it's a scroll compressor that means that something is preventing the scroll from orbiting if it's a reciprocating compressor it means that something's preventing the pistons from pumping right you like that missing from pumping physically seized and that makes sense right i mean you have this you have a machine and if something breaks inside this machine or it's not lubricated properly there's corrosion maybe it's sat a really long time and there was moisture in the system because a proper vacuum wasn't pulled it's it could seize right and so when you have a seized compressor what do you do yeah you can hit it with a hammer i have hit them with hammers but hammers actually doesn't create much force um depending on the type of compressor like a compressor like this you hear it bounce around in there so grabbing it by the suction line and giving it a good shake is actually probably going to be more effective than a hammer or maybe you know kind of getting a step stool and standing in there and giving it a couple kicks sometimes that will help i'm not even joking i see josh looking at me like i'm like i'm making a joke here it is actually it's that that's like a form of progressive maintenance yeah right progressive yeah hammer based maintenance exactly i like your vocabulary already um and now again that's generally going to only be effective with the compressor that's locked for a reason like it's been off for a long time so cool heaters are a common one they only run seasonally they may be off for eight months 10 months 12 months and now somebody tries to run it and now it could just be physically seized because of the time factor there right so in that case yeah give her give her a kick if you want now a heart start kit uh can actually work to help get it unstuck in some cases and what a hard start kit does is a hard start kit applies significant phase shift current to your start winding so it's basically giving your start winding a big hit of current now is that good for the compressor because you hear this a lot people say oh it helps the compressor run the longer life now it's it's not good or bad it can be good because if a compressor is sitting there taking a long time to start and it's running hot for that whole period then yeah it's better to get it start started quicker so some cases where our start kits make sense from the factory using a factory hard start kit long line applications 208 voltage and commercial applications so a cube smart with a long vertical line set makes great sense you have a lot of refrigerant in that system too potentially so hard start kit makes a lot of sense in those applications for typical residents with a 25 foot 30 foot line set unless the manufacturer specs it some do on hard shut off txvs then we don't use them but and then often we find that they're not necessary even when the manufacturer does back them it's one of those areas where the manufacturer specs it but then they don't provide it so obviously they don't believe in it too much and it's one of these weird kind of middle zones but the the fact is is that a hard start kit what it does is it creates a kick of current or it it adds a kick of current to the start winding for a short period of time so is it a fix to a problem the answer is yeah i mean if it was supposed to have one in the first place and it didn't have one then yes but adding it to a compressor that won't start otherwise when it should be starting it's not really a fix it's sort of a mandate it's like you're having just like you're kicking it every time in order to get it started and you know it may last forever it may it may run for 10 more years that way but it may also fail soon because it may be you know physically seizing due to poor lubrication overheating whatever some sort of physical failure inside that compressor so the only time you put a hard kid on a compressor the only time is when it's easy and even then the type you put in and the way you handle that conversation with the customer depends on the situation if it was supposed to have one in the first place then the best thing to do would be to use a factory hard circuit so for example train units their compressors tend to be quite a bit different than other manufacturers and we i've had really bad luck using aftermarket hard star kits on trains now i'm being super unscientific here because i haven't really dug into exactly why it is i could look at the specs on the two and try to figure it out and i haven't but i've found they're a little bit different it could be the microphone it could be the uh it could be the voltage of the potential relay that's different but they just tend to have issues that's what i found when you use aftermarkets so if i go to a train especially one that had a factory heart start in and i'm not going to just replace that with a kickstarter and walk away but again you're working on it you know typical unit and it's just you know it's having a hard time starting every once in a while it's going out on thermal overload which is what tends to happen when a compressor is seized it will try to start and it'll do that and then shut off that's going out on thermal overload that's a time using a hard circuit is appropriate but just make sure that you're paying attention to the situation because you may leave it on you may take it off you may return and put a factory on and those are things that just depends on the situation brand new unit for example you know six months old and it was supposed to have one in the first place because it's a long line set or a hard shutoff txb then we really should go ahead and put a factory one on uh rather than just leaving that kickstarter eight-year-old unit that you're just trying to get a couple more years out of slap a kick start on it and move on you know totally different conversation all right so that's a locked seize compressor which is the one i forgot about when i started this class the next one is the compressor that's not pumping properly and this is the one that you guys are misdiagnosing the most this is the one that that we're having the most challenge with so what happens when a compressor doesn't pump the way it's supposed to you can call it not pumping you can call it poor compression a lot of people wrongly say bad valves all the time every time a compressor compressor's not pumping it's bad valves oh my compressor has bad balance well it could have bad valves if it's a reciprocating compressor if it's a scroll i can guarantee you it doesn't have bad valves you know why because the scroll doesn't have valves right exactly so there's there's several things that can cause poor compression in a compressor and we're not in residential and light commercial we're not trying to figure out exactly what's wrong because we're not breaking down a compressor and figuring out what's wrong with it like we would with a semi-hermetic you're not going to rebuild the head on this compressor so your job isn't to figure out exactly what's going on inside this compressor your job is to diagnose is it poor compression or isn't it right now first thing if you run into this is the same way of that isolation diagnosis that we talked about before isolating the compressor you do it every time if you run into a diagnosis where you think it's a compressor not pumping a txv or reversing valve you have to put it into measure quick it's a non-optional thing it's not a well i talked to burton he said that my superheat was high and my suction pressure was high so it's a poor pumping you have to put it in a measure quick because it will slow you down to make that diagnosis correctly so when you're diagnosing a txv a compressor or a reversing valve make it your goal to be 100 correct because it's a very expensive and time-consuming misdiagnosis on top of that i'll also throw in circuit boards and i had another one in my head circuit boards damper panels anything that's weird and electronic that you're kind of diagnosing because you've gotten fed up with trying to figure out what's wrong and you just want to get out of there when you run into those sorts of expensive time consuming repairs make sure that you're right and that means slowing down and with a refrigerant circuit diagnosis that means plugging into measure quick but let's talk about what's going to happen if a compressor is not compressing properly what's the compressor's job in the first place what does it do compresses refrigerant it moves refrigerant it's what adds the energy to the refrigerant circuit to move the refrigerant through the circuit without the compressor the refrigerant moving right so what we what do we see in readings in terms of a compressor we see that our head pressure also known the artist also known as our discharge pressure goes up when our compressor's running right and our low side pressure the artist also known as our suction pressure goes down when the compressor is running right and the more compression we have the greater the differential there will be and the less compression we have the less differential there'll be proof positive by the fact when a system is not running your head pressure and your suction pressure so long as it's equalized had enough time to equalize are the same right you've all noticed that you've all observed that they're the same the compressor starts running now that differential starts happening so the first thing you notice in a compressor that's not pumping properly is what low head high suction otherwise known as pore compression ratio compression ratio is just taking your absolute head pressure your absolute discharge pressure dividing it by your absolute suction pressure that number tells you compression ratio and when that number is low it means you don't have as much compression now there's other factors and so it you can make a misdiagnosis here but these are the first things that you notice and so if it's something other than this like i've heard guys say even at caleb's the compressor's bad why is it a pressure well my suction pressure was low and so if the compressor isn't working you're obviously going to see low head pressure and you're going to see high suction pressure but delineating that from a metering device issue say a txv that's feeding too much over feeding the evaporator coil or an extreme case would be somebody has a piston and they fail to put the piston in at all so it's a it's a piston system they fail to put the piston in at all in those cases your superheat is going to be low but with a compressor that's not pumping generally your superheat's going to be high just keep in mind that if it's an extreme situation where the compressor is really not moving any refrigerant at all you're also going to see low superheat because a system that is off with an equalized refrigerant charge has zero superheat because everything is equalized so it's kind of a common misconception for an experienced technician that's not going to be a mistake you'd likely make but for a technician who is just maybe hooking up their probes and looking at a readout they see zero superheat and they immediately think oh well the comp the vapor coil is over feeding but you can also see zero superheat if the evaporator coil isn't feeding at all but again one of the kind of the the common common sense things you have to look at in terms of compressor diagnosis is is this compressor not pumping well or is it not pumping at all is it a scroll that's running backwards um something like that and then of course in those cases you're going to have low superheat but typically speaking compressor not pumping you're going to see high superheat outside this is where if you're if you're really having a hard time you get down to it's either the reversing valve or the compressor okay i would suggest that you go ahead and pull the refrigerant out weigh it out be really thorough at this point like be really thorough because it's going to indicate to you whether somebody's been doing some goofiness because you'll even have cases where a compressor's not actually failed it has poor compression because it's in bypass and a compressor that's in bypass it's going to have dang poor compression now generally you're going to hear it it'll make that kind of whistling noise but you want to make sure that it's not just because somebody you know jacked a bunch of charge in it one time i had one an old ream somebody changed the compressor in it and they filled the discharge line so the discharge line was a different size than the compressor they put in and rather than actually using a coupler they just kind of filled the gap and a bunch of solder went into the discharge line and so that compressor would immediately go into bypass and so it looked like it looked like it was a bad compressor when in reality it was just that the compressor is pushing up against this restriction head pressure is building up insanely high if you have a restricted discharge line your head pressure that the compressor is seeing is super high and the key distinction here is is that we often we're taking measurements at the ports outside the condenser and we think that is the measurement well that's not necessarily the measurement the compressor is seeing and when the compressor's seeing high discharge pressure right here exceptionally high it tends to go into bypass due to that or overheat going thermal overload whatever and this is a good kind of general concept is that be really really cognizant of what's been done to that piece of equipment and you can generally observe it as long as you're just paying attention like this compressor looks like it's been replaced that reversing valve looks like it's been replaced that txv looks like it's been replaced if you're having a recurring problem it's very possible that that's the cause and i don't mind in those circumstances having us slow down and even have that conversation with the customer to just say okay it's looking like this but there's some stuff that's been done here and um we may need to kind of take it one step at a time you know we need to redo some piping here i'm going to need to remove the refrigerant so this is what that's going to cost but we're not going to really know until we sort of get into this what that's going to be do you want me to go down this path and having that conversation with a reasonable person they're generally going to say okay what are my other options like the system is 10 years old maybe i might want to place replacer the system's three years old maybe i want to talk to the last person who is here or whatever they want to do but you want to kind of slow it down because again it doesn't take very many bad diagnosis for us to lose a lot of money and a lot of customer credibility because you know my stance is that if we make a mistake we eat it not the customer i don't like to hear stories and if you know of them then we need to go back and make it right have that conversation with me or your manager if we did something that we did wrong by the customer we made them eat our mistake then we need to make that right all the time you you really go down a slippery slope quick when you start justifying those sorts of actions so don't ever do that compressors are expensive reversing valves are expensive now here's another thing i want to mention about compressors and reversing valves a reversing valve failure can cause a compressor failure why can a reversing valve fail failure cause a compressor failure by progress is cooled by refrigerant so if that discharge gas is recirculating down the suction line for a significant period of time it can cause a compressor failure so it is possible to have a compound problem can a compressor failure cause a reversing valve failure the answer is actually it can it's not very common and we're stretching here a little bit but if a compressor is failing to the extent that it's throwing material out of it which it can you know like a compressor can actually discharge it's coming apart inside it can discharge material down the discharge line which ends up lodged in the reversing valve the reversing valve is a slide it looks like a canoe that slides back and forth and if there's crap that gets in that canoe it can cause problems just remember you do not want crap in your canoe you know right you know take a take a bag with you a cooler you know deal with that mess bury it somewhere okay i think i think we've digressed far enough there nfl txv affect the compressor can it bltx oh yeah absolutely failed txt can affect your compressor either way it fails a txt that's failed open can cause the compressor to slog a txp that's failed closed can cause a compressor to overheat and overheating uh in my way of thinking about it from what i've observed is actually a more common cause of failure than probably almost anything consistently running low on charge you know txv under feeding so high superheat and that's where checking that suction line temperature consistently under normal operating conditions your suction line temperature outside it's going to be around 60 degrees if they're keeping a little colder inside then it's going to get a little lower than that under normal operating conditions 60 degrees 55 55 probably better actually in our market that's a 15 degree superheat and a 40 degree rapid coil depends on depends on the length of line but if you see a system running over 65 on that suction line consistently that can cause compressor failure and that can be caused by a txv that's failing closed so you're doing a compressor i think it's the point jessie's getting to if you're doing a compressor it's also a good time to go ahead and do the valve if you don't know the compressor's not running um and i don't know what your current stance on that is jesse um i think it kind of depends on the circumstances but you don't want to have to keep going back um when a customer is already spending thousands of dollars for a significant repair i've found on newer compressors things that are less than five years old there's a higher likelihood it's more likely that something causes it if something kills it yeah and that's also a good time when a compressor is newer this is more advanced stuff for the senior tech level when a compressor is newer and it fails pay attention to what the manufacturer's specs say about long line um rules so if you've got a you know 80 90 100 foot line set and a compression went bad within five years look at what things we should have done with that system initially and go ahead and do that when we replace that compressor a lot of times it's a factory hard start kit crankcase heater you know shut off solenoid whatever at that point it's a good time to just go ahead and do those things because it will prevent problems flooded starts and overheating are the two most common causes of compressor failure um and that's my opinion so i'm not having a statistical analysis it'd be a very hard thing to do um but the idea that running uh flooding while running is the problem compressors nowadays are pretty tolerant to a little liquid coming on the suction line uh compared to what they once were um final thing i want to mention while we're on the topic is a maker a maker is a great tool if you use a maker in order to check for shorts that's what it's for it's not to check for opens it's not to check for locked compressors it isn't going to help you diagnose a compressor that's not pumping so don't do unnecessary tests i see you guys do this a lot well i think it might be the compressor not pumping because whatever let's go ahead and make it out no no you do that if you're looking for a short a hard to find short but again for those of you who haven't started employing the you know what i call the redneck test that final isolation test do that first start doing that you really don't generally need a maker but if you use a maker here's the main thing i want to say you never measure with a maker from leg to leg never ever there's no point in doing that test that's not what a mega is for also keep in mind if you've got the little subco maker that says bad on it anybody have this guy anybody have this guy okay just because it says bad don't mean bad so that's the important thing to know so the question is why does it say bad well it says bad because if it's an open winding motor like this one then typical open winding you know compressor application then it's okay but on a scroll it's no good a scroll is pressed into the shell it doesn't have suspension and the windings are really close to the shell and so it will measure in the low mega ohm range from the windings to the shell just because of the proximity everything's closer together inside of a scroll that's why a scroll can be smaller so if you use this on a scroll and it says bad and you replace that compressor you probably replace a good compressor got it makes sense okay so i prefer this guy here set it in the 500 volt range and measure to ground and you'll find a lot of shorts that your typical mega ohmmeter or your typical mega meter built into your multimeter isn't going to have the voltage to find especially when you have like an intermittent one because it does happen actually it's not common but you will have situations where you'll go and it'll be in the breaker's trip but it's running okay now and you know jesse that's how jesse found the uh that one contactor that was shorted we could do carbon tracing or tracking whatever you call it i kept going tracing and somebody's like it's tracking you idiot on one of my videos people are not nice on videos it was first attractive my feelings get so hurt all the time let me tell you let me tell you why the hours i've spent crying all right anything else that we need to cover jesse anybody no point being don't misdiagnose stuff if it's a reversing valve a compressor a txv a board a leak in a system make sure that you're right about it just make sure you're right about it in time um tie some of your uh integrity to that like it's your response to an incorrect diagnosis i don't want it to be oh well we all make mistakes that is true we do all make mistakes and if it was an honest mistake and you did everything you could do and you made an error chalk it up to one of those but i want it to hurt a little bit and i'm not saying i want it to hurt a little bit because i want you to have pain i just know that in order to be a good technician it has to hurt a little bit you buy that you buy that bert you hear that you had a bad diet incorrect diagnosis your response shouldn't be well that guy's an idiot your response should be well clearly the customer called back so what did i do what could i do differently how can i prevent that and if somebody brings it to you and says hey you screwed that up your response should be thank you sir may i have another not specifically but you should thank them for giving you that feedback we have to have a culture of feedback a culture of wanting to do right by the customer tie your integrity to it uh and i think you'll find that you have fewer callbacks it should keep you up at night a little bit not too much because i want you to get sleep just a little bit maybe 10 minutes you know 10 minutes before you go to sleep just a little bit of anxiety it's a lot more good forget all of this don't all right thank you guys have a good one you

Channel: HVAC School

Views: 245,111

Keywords: Critical System Diagnosis for Residential HVAC, Critical System Diagnosis, Critical System Diagnosis hvac, Critical System Diagnosis residential, HVAC System Diagnosis, residential hvac, hvac school, diagnosis, hvac school txv, hvac, air conditioning, troubleshooting, compressor, short, open, hvac training, hvac troubleshooting, hvac training videos, hvac basics, hvacr videos, air conditioning system, air conditioner, hvac installation, hvac tools, ac compressor, Hvac technician

Id: DlHDaoT_vjY

Length: 41min 45sec (2505 seconds)

Published: Mon Aug 10 2020