This episode of the HVAC school podcast, as well as HVAC our school comm, are made possible by carrier. I recently went to Atlanta to meet with some of the duck lists and vrf leadership team with carrier, and I'm really impressed with some of the hires they're making. If you've been in the business for any amount of time, you know that a company goes as its people go, and what I'm seeing with carrier is that they're hiring some real insiders and the ductless side of things. They're hiring people who actually know the business who have actually worked with their hands and they recently hired my friend Keith Ledford who's, a guy I've looked up to for years.

He was with train and then carrier, and now he's back with carrier and they're ductless division and hiring people like that makes me really believe in what carrier's doing they're ductless side, i was checking out some of the new products, especially their performance series of ductless. They have some really nice features. The one that I'm most excited about is the fact that the entire blower assembly comes out with just a couple screws, because for those of you who have worked on Douglas, you know what a pain ductless systems can be to work on. So I'm really interested in what carrier's doing is for serviceability of their Douglas products and the investment that they're making in that segment carrier turn to the experts.

This episode is also made possible by testo, as I've mentioned before, I'm a big fan of testo instruments and they have a really good quality for the price point on, especially their smart probes tools, they're Bluetooth, connected tools, moving fan of the testo 550, the test of 605, I are kind of two of my favorites. I've been enjoying the 770 3 meter. You can find all of these tools by going to true tech tools, com use the offer code get schooled at checkout to get a great discount. I also want to mention the Danfoss app toolbox.

You can look up dan Foss and on your iPhone on your Android device in the and the app stores, and you can find their free sets of apps really like the refrigerant slider. App is what I'm using pretty much every day, especially when I'm doing training, and I want to reference the pressure temperature relationship, especially on a new refrigerant and then actually, today's guest is Jamie kitchen with dan Foss. So those two things are totally unrelated: the apps division and Jamie kitchen in the training division. They really don't have anything to do with each other, but both show that there's a commitment a day of FOSS for technician, training and to back the tech, and I am very proud to work with dan Foss and I thank them for their support of the podcast.

Help me welcome the man who thinks a sling. Psychrometer makes him look like a cowboy, so he always shouts yeehaw, while using it Brian or I do think that a sling psychrometer is possibly the most visceral and childish action that you can do and still claim to be a professional and hvac. Really. Even in today's.

You know it with today's technology: there's no real good reason to use a sling psychrometer if you have good quality, thermo, hygrometer or digital psychrometer, but I mean come on, there's something just fun about pulling that thing out and sling it around in the air anyway. Today, on the podcast, we actually have a guy who came when he came on last time talked about psychometrics, and that is Jamie kitchen from Danfoss jamie is hailing from canada, and i will confess that the audio in this episode isn't quite as good as i normally Like it to be, but we were doing it over a phone app and I think it works out, I think you can. You can hear it okay. So we talked about thermostatic expansion, valves, TVs, TX, vs and Jamie talks about some things that, frankly, are new to me.

Some new ideas and I'm sure they'll be new to you as well Jamie's, a smart guy and I'm glad to have him on. And so hopefully you get something out of this. I did ask Jamie what makes Canadians so special and the answer frankly shocked me avoid any speculation. I will now allow my precious Tiger blood to be extracted there.

You go those who deserve it now and possess it. Use it wisely, I trust that you will how's things it's going well, actually I can't complain good weather's been kind of suckish, but other than that any bed. I always throw it into a learning opportunity, because this is the kind of weather where it's really hard to do you modify. Ah, so what kind of weather is that in Canada? Generally, if you look at your charging chart for a piston you'll notice that on cooler days with a higher latent load, you have tons of superheat when you have lots of super.

What does that do to your average evaporator temperature? Ah, it pushes it up right. So you go further away from your apparatus dew point, and this of course kills your dehumidification winning that's exactly the time you need dehumidification and not sensible cooling right got it yeah, that's actually interesting. So the first thing to ask there is like how many systems are still being shipped with fixed orifices. I mean it seems like that's pretty much a dying breed.

Isn't it yeah, seer 13 came in in 2006, so previous to that date, let's just say five million units shipped, you know, four million of them of the vast majority or Pistons come seer 13 that pretty much flipped on his head with the vast majority going out Being TXV because the TX V's just allowed for not only better or more optimal, evaporator fill over various ambient conditions. It also resulted in a tight shut off when the system shut down, and this maintained your differential across your metering device and across the system. So your compressor had to do less work, rebuilding those optimal conditions again on startup and the more you start, the more impact this has on your efficiency over a period of time say an hour, so those two things combined gave the seer 13 effort a big shot. The arm, because, just by going to a TX valve, alleviate a lot of the issues that were required to get to C or 13.

They weren't all of them. But it was a big jump, good stuff to get started with at least it was sort of a perfect intro and that's all because the Canadian weather is what's the average outdoor temperature up there right now, right now, it's C i 60s low 70s and rainy. It's a little sunny out right now, but there's a substantial amount of humidity in the year. You don't run the air in those types of conditions.

Do you know? Generally we have a dehumidifier in the basement like a standalone dehumidifier that we empty on a regular basis. Just to keep the basement dry and we just open the windows in the evening time so again we're cooler than normal this time of year. We should be in the mid to high 70s with you know, generally drier weather should start kicking it around this time, but last few years, adjustment up and down that's either one side or the other. So, let's start with just the term, because I think I've actually had some questions from guys who asked you know what's in between a TX V or a TX valve, or a te v and really they're just names for the same thing right.

What do you call it typically um? I generally call it a TX v if somebody refers to a TeV I'll, just refer back to them as a TV, your marketing people will generally sometimes dig in a bit more because they want to stick with a certain protocol. I'll call it but the most part, I really don't care, I mean TeV. You really want to take the acronym for accuracy with. You would make more sense, but we've been calling it TX v for so long now that it just seems to slip off the tone.

So let's address right off the top, because I think a lot of texts are going to be listening to this already with a bad attitude about TX V's. So, let's address those feelings, those emotions, first of all, the elephant in the room. What do you think causes the high failure rate that some people see on expansion valves? That's a good question. I'm going to just go back, I guess and reference our you know our warranty pile you'll hear me speak a lot about the warranty pile and it's something that, as a junior engineer, we kind of get stuck in and the reason I refer back to that is Because the gives you indication of why stuff is being returned from the field so again it follows a lot of we talked about in compressors.

Generally, you can't really flood a TX valve, but what you can do is adjust it way out of whack, and so what we'll find is TX fees that have been adjusted. Their superheat has been adjusted, either very very low. When the report comes back at the valve, ISM controlling or it's been put very high, and the report is that the valve is not responding. In other words, the valve is closed.

It won't open and it just is almost counterintuitive to what you would think. The other big issue we find is overheating. Generally, people, I think when bells are raised in my understand, is that you wet wrap this valve so that it's almost you know, unrecognizable, and then you apply a lot of heat very quickly to the connections because you're in a battle against time, you're heating, water up We'll just turn to steam and if you know like we talked about you put a pot of water on a burner, no matter how much heat you place on it, it's never going to get any hotter. The steam is going to escape and take that heat with it, and this is what is happening, that wet rag is basically in a race with you to remove the heat as you apply it, so it is actually better to apply more heat quickly to the area.

You want to braze before it can travel up into the area where the wet wrap is and carry that heat away. Believe it or not, the result of not applying heat fast enough is you're going to run out of moisture against the surface area. You may still have moisture on the other side of the rag but you're going to dry it out on the inside against the valve. This will stop heat removal and allow the valve to climb and temperature, and we get these valves back where they've been heated.

So much that diaphragms distorted the sensing bulb is actually leaking only because of the great buildup in temperature, so again practice braising them in until you get very, very good at it and the reason I say that is, for example, at a trade school we donate all Kinds of valves that we can't sell for various reasons and we donate them to schools - and my point - is that I'd rather have the students in a trade school raise these things in over and over and over again. They can do it in their sleep. Once that's done, you've eliminated almost half of the reasons why these things fail. Now, when I say that I'm not talking about systemic failure, I'm not talking about something happening in another part of the system where the valve becomes plugged or something that has absolutely nothing to do with the TX valve itself is occurring.

This, of course, makes up for the other third of the failures that come back and we've got a list of all kinds of things where TX valves are getting plugged, they're full of junk, there's minerals in them. There's leftover a debris and everything else they come back. Unfortunately, once the TX valve gets plugged, unless it has a removable screen, it's done, I hate to say it no fault founds in there as well. You know a certain proportion of what we get back is we can't see anything wrong with it.

We put it in our test, stands we fire it up? You know we even take some of them and throw them in one of our refrigeration trainers and they actually work fine, and we just can't figure out why these valves were actually returned and again, I think, a big part of the superheat miss adjustment comes from people, Not understanding what should happen or what does happen when you adjust super udana TX valve. I wanted to get that out of the way right off the start, because I think some people start hearing about TX es and especially when we're talking about the positive attributes of a TX being a lot of technicians, sort of shut down and think well, it would Be better if we just went back to Pistons, I definitely fall into the category of a tech who has replaced a lot of expansion valves that were actually failed. The bulk of them were failed because of bulb issues, meaning that when they're actually failed failed either because you know the bulb, vibrated and snapped, which happens on certain brands. We run into a lot of those cases.

It lost its charge and then also because of, like you said in issues with overeating and then issues with them becoming contaminated and a lot of that has to do with proper refrigerant line handling in the first place. So when you do a new install in Florida and you're, not careful about not getting the lines in the dirt and if, let's say your liquid line, filter drivers inside the condenser, which it is in certain brands. And then you start that thing up, and the first thing that happens is that sand and dirt slams right into that expansion valve. So that's a reason and then also the majority of technicians don't flow nitrogen in our market, and I think it would be safe to say that the majority of technicians across the country and the u.s.

do not flow nitrogen while brazing and so depending on the level Of oxygen, that's in the lines you'll get varying levels of carbon buildup, also depending on the amount of heat that's used, and so I think that's also why certain people get more failures than others. You know. First of all, you should be filling nitrogen while you're brazing, but even if you're not it depends on the way that it's being handled because you get a lot of technicians who say you know, I haven't flowed: Evon, fluid nitrogen, my integrity, I've never had an issue And I think sometimes, when you're dealing with situations where they've gone straight from having nitrogen in his system to a fairly closed circuit and maybe one port open and then brazing, that's different than somebody who's say brazing in a reversing valve, where all the lines are open And they're using really high heat, raising it in and then all that carbon ends up in the expansion valve as sort of a nuance to look at it. But those are the reasons that I generally see.

Rarely do I see that the actual valve itself is just literally something wrong with it. It's almost always something external to it, with vibration being thrown into that same category where it vibrates and then ends up cracking the bulb tube and the vibration isn't an issue only 40x valves and pressure controls and temperature controls, even connections on compressors or under that direct Attack all the time by vibrations in the system. So yes, absolutely all right. So with that out of the way now, let's actually talk about the expansion valve, what is the job of an expansion valve? What does it do? Only job with any expansion valve is to meter the refrigerant into the evaporator to match the heat load on that evaporator, so every pound of refrigerant that boils from a liquid to a vapor absorb, so many BTUs per pound.

So if you want to balance the heat load on evaporator, you take your heat load and BTUs and say BTUs per hour, and you divide that by the amount of heat that's absorbed by each pound of refrigerant, and that's how many pounds you need to put through That evaporator in an hour, so the job of the metering device, is to ensure that you get the correct amount of refrigerant flowing through your evaporator to absorb the heat and as well. It needs to ensure the conditions in the evaporator or such that it does. The job as supposed to do, whether it's sensible, cooling or a mixture of sensible latent cooling for air conditioning, whether it's medium or low temperature duration, the pressure in the evaporator, has to reflect the application. So those are the two jobs that the metering device does with a fixed orifice, whether it's a cap tube or a piston.

It is exactly that it's an open and the amount of flow that goes through. That opening is based all else being the same. The diameter or length of the cap tube the diameter of the opening of the piston and the pressure differential across it. So since you can't change the diameter of the opening, only the pressure differential across the orifice will cause the flow to change.

So, that's why, on a hot day with high condensing temperatures compared to your evaporator, you will get much higher flow through it. You'll find a higher evaporator temperature. Since you know a higher boiling temperature of the refrigerant and you'll have much lower superheat, whereas on a cooler day say with a lot of moisture in the air, so you have your latent load. And again, all you need to do is look at the charging chart for a piston.

You will find that you will have very high superheat because you just don't have enough flow through the evaporator to match your load. This is where the TX valve shines. The TX valve is what we call the adaptive control and by adaptive we means it opens and closes. It adapts to the change in heat load, and it does this with the sensing bulb.

So a picture you're sensing ball buys a little miniature refrigeration container. That has an opening with a hose on it that goes back to the element or the power head of the TX fell at the top of it. So it's sitting on top of your suction line. Now imagine you increase the heat load on that evaporator.

You suddenly have more moist air coming across it. You suddenly have a heat load, whether it's in refrigeration or air, conditioning generally - let's say: refrigeration, you're walking with a whole bunch of warm product, and you put this in your walk-in box. Suddenly the amount of refrigerant in the evaporator isn't enough to absorb all that new heat, so the liquid runs out sooner, which means it has more time to warm up as a vapor, so the vapor rises in temperature and when it does so, it runs past that Sensing bulb, the sensing ball, picks up that heat and some of the liquid in the sensing ball boils and the vapor takes up more room than the liquid does so the pressure in the sensing bulb arises now, because you have that cap tube running to the power Element on your TX, well, that pressure is transferred to the top of the TX Val, so the TX valve is kind of like a balance beam, so to speak on its side, where you have underneath pushing up the evaporator pressure and spring pressure and I'll get back To that, in a little bit, and on top you have this pressure from the sensing bulb so picture a line with a sensing ball pressure on top and the evaporator and spring pressure underneath. Well, when that ball pressure increases like that, it pushes down on the diaphragm and the force it's pushing down with now becomes greater than what's underneath it, the evaporator and the spring pressure.

This forces the valve open and the valve now opens more putting more refrigerant into the evaporator to match the new heat load. This results in somewhat of a drop in superheat and more refrigerant flowing into the evaporator now to take care of that extra heat and, of course, vice-versa occurs. Tx valves aren't as successful to pressure differences like a piston. Is they just require enough pressure in order to be able to feed properly? So I'm not sure if you understand how say a gas valve works, a gas regulator it'll always give you three and a half inches of water column pressure out as long as you have a minimum amount of pressure going in it just regulates the pressure right.

It can't create pressure, it just regulates it and that's very similar with a TX valve. The TX valve will cause a pressure drop and it will offer enough refrigerant as long as there is a great enough pressure difference across it, so that isn't a wrap-up. How a TX valve works, it senses the temperature of the refrigerant leaving, if it climbs compared to the saturation temperature in the evaporator it signals it needs more refrigerant. It then opens up and puts more refrigerant in this is where an understanding of superheat and sub cooling come in.

You have to understand that a TX valve doesn't maintain constant superheat right. It requires an increase in superheat in order to open the valve. So if you look at the opening curve or the opening profile of a TX valve under high load, you will have higher superheat than what you will have under low load. So if you're in pulldown mode or you have a high latent heat, you're going to have higher superheat, if you're almost satisfied or the air is very dry in the house, say, for example, you're going to have less superheat, you won't see the climb in super heat.

Lucky wood with a piston, but let's look at that spring because you need to compress that spring underneath in order to open the valve that spring is going to push back harder as you load it. So it's going to require a greater force on top to hold that valve open against that increased spring pressure, and the only way to do that is for the sensing bulb to be warmer. So the sensing bulb is going to have to be a few degrees warmer than the saturation temperature to keep that valve fully open or open more than it would say compared to when the valve is almost closed. So, instead of seeing an 18 degree rise in superheat or 12 degree rise in superheat with a piston, you may see a 3 or 4 degree rise and super heat with a TX valve, but it will not maintain constant superheat in the evaporator all right.

I think some people are confused about that. So let me ask you a question just out of curiosity good, if I were to mention factory or static superheat. What would you tell me that means factory or static superheat? They use them interchangeably. Ok.

Now we think that means design superheat a constant superheat. It's designed to maintain yes feed right into your desire. For my question, that's a very popular answer and unfortunately, it's wrong static. Superheat is the superheat required to overcome the spring force.

The spring is never completely uncompressed. In a TX valve, ok, it's always going to push and it's designed to push down with a certain amount of equivalent force. So this brings us to nominal capacity and things like that so 45 degree evaporating temperature, air conditioning situation. If your valve has 7 degrees on the side of it, okay, that means that it will not even start to open up until you have seven degrees of superheat.

That is the static superheat. So the valve is fully closed until you have at least seven degrees and when you modify your superheat, you take that dial and you turn a clockwise to increase it or counterclockwise to decrease it. What you're affecting is the static soup reach setting on the valve? So once again, it is not what the valve is designed to maintain. It will never maintain a constant superheat.

The superheat is going to change based on your load, so the valve won't even open until you actually hit your static. Super ecstatic means not moving, and so that's where that comes in too now engineers like to make lots of things out of nothing. Okay, I don't mean that literally, but we have multiple super eats. The second super we talked about is opening.

So if I were to go talk to an OEM engineer - and they would ask me what is the opening superheat on this valve they're, talking about how many degrees of superheat is required above static, to give me the rate of capacity of that valve? So, between being fully closed and being fully open, let's say the rated capacity is one ton. I may need five or six degrees of opening superheat on top of static before my valve gives me my capacity now, if you add those two together that gives you operating superheat and operating superheat is what everybody refers to when they measure superheat at the vaporators outlet. So somebody calls me and says I have 12 degrees of superheat at my evaporator outlet, they're referring to operating superheat and if the system is under load, it'll be five or six or four degrees, at least above the static or factory superheat setting on a TX valve. That's where that value comes from very interesting.

I've literally never heard that before ever know. So this is me learning here, as I listen make sense, though, because it's often what you'll see you generally, when you measure the actual superheat on a system with a factory valve you're generally going to see superheats that are then what the valve will often say. Hmm - and I guess that kind of makes sense - yes interesting its alleviated a little bit by the rise in evaporator pressure in the evaporator as you dumped more refrigerant in but again it's always going to a result and a little bit more superheat under high load than What you would get say when you're almost satisfied, so I just thought that's an interesting thing. So remember: it's not uncommon for a system to have high levels of superheat and when I say high levels of superheat, I'm not talking 40 degrees, I'm talking 12 14, whatever it happens to be out of your evaporator when it's under high load.

The last thing we want somebody to try and do generally is a just superheat when you're under load, because if the system is doing what it's supposed to do, you're going to be hitting a moving target. In other words, your soup reach should be dropping as the load is satisfied in the space. So the key thing here - okay or maybe for shouting a bit - is if it's doing this job, if you're not making pulldown - and you have really high superheat - that's a different story. Now you need to go out and find if you're high superheat is related or not right, but you need to take other things into account.

This idea that a TXV maintains constant superheat, I think, is caused quite a bit of confusion in the market, and you know I can't blame people because hey we talked about Pistons prior to 2006, there's a lot of people that never ran into TX valves or very Rarely ran into them unless they were in refrigeration and even then, if they did commercial refrigeration at the time it was a cap tube. So when TX V's came on the market, there was a huge effort in education and training for people, because again there was just not this knowledge available. I think another part of the issue that makes people upset is this. Tx valve is like this little black box.

In a lot of OM, TX valves aren't adjustable for super you, in other words, nothing to fiddle with there's nothing. You can physically change on it to make it work. So if there is something that's not working, it's pretty easy to see this TX Vail and think. Oh man, this must not be doing what it's supposed to do, because the conditions in my evaporator aren't what I want them to be.

The system is not pulling down whatever I'm going to change this TX valve up because there's nothing else. I can do with it. You know - and this is where the whole systematic troubleshooting you know, as you mentioned earlier. Very rarely is the TX valve itself.

That is the source of the problem. Rather, it's just the collector of dirt or you know the thing: that's feeding the evaporator, that's closest to where we're picturing a problem. So I get that part a hundred percent. So maybe we can spend some time just going through.

You know. Yes, we'll talk about TX valves and best practices, but let's look at some of the other things that may be causing problems that isn't the TX valve all right. So in today's tooltip corner I want to bring up a couple things that come up a lot when you're talking about digital gauge, manifolds and so first off. I and I said this much times, but I just want to restate it because a lot of technicians ask you know.

Why would why would you want to go digital and you know all it does, is just do math for you. Well, it's not quite that simple. An analogue set of gauges does not have the level of accuracy that a digital set has and so accuracy and being able to have all of these measurements right in front of you in one place is one of the big reasons that you go to digital, not Because it does a superheating sub-cooled calculations for you, because that's not a big deal, and so for those of you who, like looking at the needle. I like looking at the needle too but there's reasons why you may want to consider not doing that anymore.

When it comes to accuracy, one of those reasons is is that most of the thermometers that we use to measure line temps are k-type thermocouple. You know that it's little, you know it looks like the little tiny pitchfork you know with the two prongs that we use and there's a lot of manufacturers that use that and it works okay, but it does not have the accuracy of a thermistor type measurement. So the test, Oh both their smart probes and the 550's 557 s. They use a thermistor instead of a thermocouple, which means that the both the pressure measurements going to be better than what you get on analog and because you're using a thermistor instead of a thermocouple you're, going to have less variance, which means that instead of you know, Potentially, having a situation where you think you have 10 degrees of soap balloon, you actually have five you're going to be much closer to that 10 degrees of so cool.

If that's, what your target is, so there's an advantage there, but there's another couple things to think about: there are some manufacturers of manifolds who integrate the micron gauge into the manifold, and Jim Bergman talked about this in the last podcast. That's really a bad idea, because you want your micron gauge to be reading as close to the equipment as possible, and you want to be able to valve it off in a in a very solid way and actually valves off way. In order to measure your decay and the only way to do that is with an actual vacuum, rated core tool, because your your handle on your on your vacuum pump, isn't sufficient for valving the system off, and so, if you are doing it even on the handles Of your gauges, those a lot of times, the seals will leak under a very deep vacuum, so you need to be able to do it on a vacuum rated core tool. Well, if the, if the engage is built into your manifold first of all, you're pulling through a manifold you're, probably using quarter-inch hoses, the manifolds are restriction and it's closer to the pump.

Now your micro engage is closer to the pump than it is to the system, and you want it to be closer to the system. When you do decay test, you want to be as close to the system as possible. Well, the test. Oh 557, it has a micron gauge, but the micro engage is external, so it's a separate micron gauge.

Then it attaches back to the actual head unit, the actual manifold, which is the right way to do it. So you have the data there on the manifold that you're used to using it's right there with everything else, but it's a separate sensor that attaches to the system. So you can do a proper decay test, which I think is a really nice really nice thing and then that's probably my favorite thing about the 557. Is that option, and it also has the additional you know, port for the vacuum.

So if you're gon na, if you're going to pull a vacuum through your manifold, I think the 557 is probably the best option and again this is my opinion. I'm not saying there's anything wrong with the other brands per se. But for this reason I think this makes it a superior. Now again we don't even suggest you pulling a vacuum through your gauges, and so you can still use the 557 without pulling through it.

If you want, you can still use the micro engage on it. You just aren't going to have your hoses connected to the system anymore, so and it's a little bit confusing, so the thermistor is a thermistor or something to look for having a vacuum gauge, that's not built into the manifold itself. That's external to the manifold is something to look for and then finally, the other thing that I suggest is look at temperature compensation. There are some even even the tests of smart probes, for example, they're, not they're, not temperature compensated and so with very, very fine pressure measurements.

It's going to be affected by the temperature, so, for example, you wouldn't want to put - I don't know a case where you would do this, but you wouldn't want to take a pressure reading in a highly highly variable temperature environment when you're taking regular pressures. But when you're measuring vacuum, that's where it becomes really important, because you're reading very very fine changes, and if it's not temperature compensated, then you're going to read all over the place and so the 557, the 550's they have temperature compensation built in which makes it makes A big difference, especially even when you're dealing with things like this standing pressure test to see whether or not you're you're dropping pressure over time with a nitrogen test. Temperature compensation is also important and with those types of readings, so there's a lot of reasons to look at temperature compensation. All this to say when you're buying a manifold where you're looking at something to take superheating, sub cool and take system readings, look at temperature compensation.

Look at whether or not it's using a thermistor or a thermocouple and think about the location of your micron gauge if you're going to be measuring vacuum with your manifold set. Alright, that's enough for me: let's get back to Jamie! I guess I need to address this because I've said on this podcast before I've called a TXV, a constant superheat valve and frankly, I never considered the idea that you do have increased spring compression and the fact that there's always going to be a lag in response To so, your superheat has to increase for that valve to open, which makes perfect sense. Yes, but it is important to at least recognize that the superheat is an indication of evaporator load. Yes, and so, while it's completely true that it is not a constant superheat valve in that sense that it always maintains exactly the same superheat, the intent of the design is to maintain the proper amount of refrigerant flowing through the evaporator coil, to match the load and Superheat is a measurement that we take.

That indicates that so the two are very closely related to each other, just not constant in the sense of what you're saying that say, you have a refrigeration box and you fill it full of product. You can't expect that expansion valve to run exactly the same superheat that it ran when it had no product in it or you can't expect a system that's running at a high humidity day, to run the exact same superheat that it runs on a very low load Day, for example, so I wanted to address that and then let's go over quickly the forces. So you talked about this. The spring pressure is closing pressure, the evaporator pressure, which is often on the outlet of the evaporator on the external equalizer.

So it can be either internally or externally equalized, but most modern expansion valves that we see are externally equalized well in air conditioning. That's an important point. Actually, we have a second to touch on go ahead. Do that yeah! Okay, the external equalization connection is there for a reason, and generally you know, I'm not big on rules of thumb, but if you have a distributor now that we're it's a refrigerant distributor, in other words, you have a multi circuited evaporator.

Your default should be an external equalized valve here's the thing: if you install an externally valve you, don't really need one you're, fine, install an internal equalized valve and you need an external equalized one now you're gon na have problems because generally the TX valve, if its Internal equalized an only sense pressure right at its outlet, in other words, that outlet pressure is allowed to travel up under the diaphragm. If you have a distributor downstream of that, that causes a pressure drop and all distributors cause pressure, drops sometimes as high as 20 pounds per PSI or more. The result is the expansion valve. You know I hate to use a word thing because it doesn't think at all, but it thinks that the pressure in the evaporator is 5 10 15 20 pounds higher than it really is, and that higher pressure is up under the diaphragm.

Now, when you combine that, with the spring pressure underneath the diaphragm, what is applying pressure on the other side of that diaphragm, your sensors, the ball correct right now, you're sensing bulb is measuring superheat, which is the rise of temperature above saturation, saturation is determined by pressure. So, with the pressure inside your evaporator, let's say is 10 or 15 pounds less than what the TX valve thinks it is. That means your saturation temperature is also correspondingly lower, let's say 6 or 7 degrees lower than what the TX valve thinks it is. So if you need 7 degrees of superheat to open up the TX valve, but the evaporator 6 degrees less than what it thinks it actually is, you're going to need 7 plus 6 degrees or whatever the saturation temperature drop, is across a distributor in order to open The valve so the greater the pressure difference between the outlet of the TX valve and where the sensing bulb is, and you use an internal equalized valve the more or the equivalent superheat is going to be required to open the valve.

So if you have a 5 degree drop across a distributor you're going to require 5 degrees of higher superheat to open up the TX valve, so you're going to constantly under feed the evaporator. If you use an internal equalized valve in a high pressure, drop multi, circuited evaporator, it's interesting, I never made the connection. I always knew because the pressure drop across the evaporator coil, but I never made the connection in my brain that yeah distributor is what's going to be, creating that additional pressure drop on one coil over another coil. It's very interesting.

It's almost like you have a second metering device in place in addition to the expansion valve. Well, in a sense, that's what you actually have. Yes right, you literally have two metering devices in a rural really in series and that's an interesting point, but that's where the external equalization connection comes in because it takes the pressure. After all, these pressure drops where the sensing bulb actually is located and applies that pressure up under a diaphragm, the evaporator out of the TX v outlet to the evaporator okay, that pressure is not allowed up under the diaphragm in an external equalized valve.

It's sealed off. Only the pressure coming in from your external equalization line can be applied under there. That's why you never ever ever seal off that external equalization line, even if you don't need it, because the valve will not work, it always has to have access to the system. All right, that's something that we've, probably all seen at one point in time is a technician that says well, the old one didn't have this tube, so I'm just going to seal it off.

Well know if your new one has the tube it's using that as the actual pressure point to access evaporator pressure, to put it up under the diaphragm, and so that's actually the opening force. Now. One thing that's interesting because I had been saying for years that if you have a plug or crimped external equalizer, because the external equalizer is the opening force, I'm sorry is the closing force. I think I said opening force earlier, because it's the closing force of the valve that, if you have it, crimped that the valve will go wide open.

What I found out in practice is that the valves will actually often leak some static refrigerant into those equalizers and in fact it will actually cause the valve to slam shut. I didn't realize that and then I had some kind of expert refrigeration. Guys say that yeah I mean you can see both, but you actually will see cases where a sternal, equalizer, being blocked or crimped shot will actually result in lower section pressure, lower evaporator pressure, and my thought was always that it would be higher. Have you seen that at all well yeah see if it's plugged, then generally you can't force anything out of it.

So when you try and push the diaphragm down, especially if it's got liquid in it, you can't compress a liquid. So you can't close that valve down right, so it's actually literally going to stay in the one position it's going to be in you know, that's a good point. I'm trying to visualize it in my head so that if it's trapped with a high pressure underneath it, you can't relieve it if it's trapped with a low pressure underneath, you can't relieve it. So I guess it all depends on the thrill the die right, but I would definitely know the valve would be very laggy.

You know it would be very, very, very slow to react in that case, almost like a pressure control where the capillary tube or capillary tube. If you guys call them is full of oil, you know you're trying to push this oil through a small diameter tube. It's going to move a lot slower than the gas pressure would result in a much slower, reacting control. That's a great thought, yeah and I always just said I said well, you know if it's scrimp, then you don't have that closing force and if you don't have the closing force, then it's going to go wide, open right.

That made sense to me, but as it turns out, it really just depends on the particular situation and the particular valve too so. Yeah anyways a good point interesting stuff. So but it still is good to know that if you have an externally equalized valve that external equalizer acts as a closing force, the spring acts as a closing force and the bulb acts as an opening force. Which is why I'll do the old practice of taking the bulb and warming it up in your hand, you'll see the valve open because more pressure is being exerted inside that bulb, as you add, additional heat to it, which then acts as an opening force to drive The value and that's a great tech tip you can throw in here right that it's doing two things you're one checking your bulb charge to see if it's still good right, but two it's kind of one of those last-ditch things you can do that instead of dialing, Your superheat all the way in you know until the screw practically falls out just hold that bulb in your hand and if the valves got a whole unit, not so much of the filter screen but say it's got some crud in the actual stem somewhere.

That's causing a lot of stairs cysts or whatever it's recess right. You can apply enough pressure Rachele across set by the heat of your hand too often overcome that gumminess and unstick the valve. Now, obviously, the problem hasn't gone away. You've just put a patch on it.

You still got to figure out why the valve sticking, which means you probably have to clean the system. But my main point here is you identified where to look? Okay and that's you know, key to any troubleshooting is eliminate as many possibility as possible. So you know where to focus on so anyways. I just throw it out in there sure it's a good thing to do.

The one thing that I see Tech's do sometimes is they do something that they've been taught to do like warm up the bulb, but they don't know what it means when they're done so they want a little bulb and they say: oh okay, so my section pressure Went up okay now what it doesn't have any significance or meaning. So let's go through some common diagnostic steps of diagnosing an expansion valve. So, first off I guess, let's address the issue of why most technicians start looking at the expansion valve and I think it's generally for the bulk of technicians out there. It's just as simple as I've got low section pressure.

I've got low, suction pressure. I've got some sub cool because I've got some sub cool, I'm pretty sure it's not charged. So now, I'm going to start blaming the expansion valve so speak to that a little bit. Okay well get the nail on the head.

First of all, I congratulate them for actually checking the sub cooling at the condenser outlet, because the sub cool and the condenser outlet is generally your indicator that it's not a refrigerant charge. So, looking at your evaporative, your evaporator pressure is low and it's multi circuited. Look for changes in between circuits, let's say: you've got five or six or eight circuits. You can have multiple circuits that are plugged either with oil or kinks in the line or whatever it happens to be, and this can literally drop your pressure substantially in the suction line, because the header collects all these different circuits together.

So it's not so much a TX valve problem as a distribution problem. Okay, an easy way to do that is get specially. If you've got one of those infrared thermometers, everybody sees you shine that on your coil and it will give you a beautiful temperature profile of the coil okay and if you see certain circuits that start off at very low ten but end up at much higher temperatures. Because they don't have much refrigerant in them and that's an indicator that you're starving certain circuits - and this is going to be an issue that needs to be corrected.

It has nothing to do with the TX valve generally, but it still needs to be corrected. So little things like that, if you happen to have a TX valve that has a removable filter in it, you can check that, but even before you get to the TX valve, look upstream! Okay, yes, you've got sub cooling at your condenser, but let's change this into electrical situation. If you happen to have 24 volts at your control transformer, but you have 0 volts at your control relay. What do you generally do? What's your next step, you might you got to move down the line, see where you're losing it absolutely.

I can show you pictures of filter dryers where the last 1/2 or 3/4 inch of that filter dryer is white and it's not frosted paint that we put on there it's ice right, because the filter dryer is plugged Sol novell is not functioning properly upstream. There's evolved in there valve somewhere in there that somebody forgot to open properly. There's all kinds of things that you need to check upstream and to be honest with it's very quick, just go along with your hand and if you happen to feel a temperature drop or if you happen to hear something with your ears or see it right. There's a good indication that there's a pressure differential across there again, if you want to get more precise, you know you can use a thermocouple with a little bit of insulation, just walk along the feel across each component.

Remember there's a lot of times when you only have 4 or 5 degrees of subcooling, and this can occur when it's low ambient it can occur when you have low load things like that, it doesn't take much pressure drop to eat up 4 or 5 degrees. So once you get flash gas feed in the meter device, especially if it's excessive, you can't push much vapor through a TX valve. This is going to drop your evaporator pressure substantially. Okay, if the evaporator pressure is not very low, let's say it's supposed to be 45 degrees and it's 28 degrees.

You know you got a picture. What Tx valve does if you have reduced air flow on your evaporator coil, let's say you got a plugged air filter. What's that TX valve going to do in response to the reduced load on the evaporator, it's going to slam on down it's trying to feed it with the proper amount of refrigerant. It's saying we got too much exactly it's going to throttle closed.

Now you got a fixed speed compressor. What's the only way for that compressor to balance the amount of refrigerant the TX valves putting in there if the TX valve reduces the refrigerant flow? What's the only way that compressor can balance out reduce flow? The only way to do that is for your evaporator pressure to drop the lower the evaporator pressure, the lower the pumping capacity of the compressor. So it is natural for the evaporator pressure to drop when the TX valve closes, because that's the only way, a fix, P compressor can balance that reduce flow and that's exactly what the system is trying to do all the time. It's trying to find its balance point.

My question would be how much superheat do you have if you've got a 30 or 28 degree evaporator temp and you've got 8 degrees of superheat. It ain't a TXV problem. It's an airflow or load problem. Now, if you've got a 28 degree, evaporator and you've got 30 degrees of superheat.

Now it's a refrigerant flow problem. Okay, it's not a load side problem, so those two different results right. There require a different approach to the problem. Airflow is not going to be fixed by putting a new TX valve in there.

That has to be addressed. In other words, you need to find out. Why am I not having any heat load? Is my evaporator iced up like a complete block? In other words, maybe my airflow was a little bit low to start with, I started building ice. I started building more ice, which acts as an insulation.

This reduces heat flow on and on and on and on it perpetuates itself or, do I have say, a block filter or a block screen of my TX valve and I've just not getting any flow through it, which case you would end up with a low evaporator Temperature and very, very, very high superheat. Now in this case you would see ice on the inlet of the circuit, because you do have a little bit of refrigerant going in there. Okay and it's below freezing so you're, going to have ice on the beginning of the circuit, but the rest of the circuit is going to be very, very warm okay. So this is a good indication that you don't have enough refrigerant going into the evaporator.

That's all that tells you. You can firm your refrigerant charge with your sub cooling. That is not a refrigerant charge problem you check upstream, to eliminate any possible blockages that could be causing flow issues. Then, once you remove that possibility now you focus on the TX fill okay, so you can try adjusting superheat generally.

If you try adjusting superheat as soon as you try reducing superheat, you should see an immediate response if the valve is reacting. So if the valve is reacting, it's got a proper bulb charge and it's just a superheat problem. In other words, somebody was monkeying around with your superheat. Before you got there, then you should see an immediate response.

When you try and reduce superheat, the valve will immediately open up your evaporator pressure. Will increase you'll have more refrigerant flowing through the system, so now what you need to do is you need to adjust it in the case of AC, for example, some of the AC valves. You can back them all the way in and then so many turns back out and you hit factory setting again. Otherwise, if you don't see any change, when you adjust the superheat, that means either the valve is plugged stuck or you've lost your bulb charge, one or the other.

So, unfortunately, at this point you can try holding up bulb in your hand, to see if the valve pops, in other words, pops open. If not, here's what I recommend you do when you pull that valve, Oh rather than just replacing it - and this is very important rather than just replacing it if it's got a removable, orifice pull an orifice out and look at the screen. If it's plugged, you have to ask yourself: why is it plugged where's my filter, dryer? Why didn't the filter driver pick up on this? It's an important question because if you just stick that txfl back in there again, you got to ask yourself if that filter, guy didn't capture, this debris was to say that there's not more of this stuff floating around that can possibly plug this generally. I would recommend flushing the system.

You don't want to have your TX valve act like your filter driver. It is not there to clean the system up, that's not just job okay. If you've got a split system and your filter dryers, you know 30 feet away on your liquid line. Try moving it closer so that it offers you know better protection.

Maybe there's a lot of work done on that liquid line upstream of the TX valve. As you say, people didn't use, nitrogen doesn't take much of that copper oxide to block that screen on the TX valve. So maybe move the filter driver closer. But my point is you've identified why that TX valve failed.

If it's a removal, orifice grate, just clean the screen, put it back in again or even if it's a fixed orifice. If you look into the liquid wine inlet of the TX valve, you will see the screen at that screen is plugged with black stuff. Then you know it was contaminated, it's important, because you have to understand why the TX valve failed before you can replace it. Just like a compressor or anything else.

How could you guarantee it's not going to fail again until you have cleaned up or REME the reason why it failed in the first place? Okay and just my own curiosity as a tech, I always wanted to know - I just hated replacing something and not knowing why it failed, because I was never guaranteed. It wasn't going to happen again and it just bought me, but that was just me so to me. That's a big deal so also, if some of that stuff makes it past that screen and into the distributor lines was to say that it isn't going to cause problems there as well, so just flush the system clean it up, replace the valve during your commissioning, make Sure that it runs properly pulls down. Okay, things like that and away you go, but again don't automatically is and just replace the TX Vail with at least taken the steps you mentioned before absolutely yeah, and so here's what I would say, because I think, as we kind of travel through these conversations and Times it's easy to get kind of lost in it so start here.

We're going to just again refer to the issue of seems, like my high side sub cooled, liquid temperature /, condensing pressure is about what I would expect, but my suction is low. This is where Tech's start with: okay, maybe it's the TX V, and so before you start thinking the TX V, let's really identify, is it a load issue, meaning we don't have enough heat load on the evaporator coil? That would be low airflow. That would be, I mean it's primarily low airflow, but it could also be the actual low load in the space. You could have somebody who set their thermostat to 62 degrees and let it get down there and then that of course, would be low load as well.

Florida, especially because we always set our units at the hairy edge of freezing in order to remove as much latent load as possible and makes it, but anything that causes low load that can cause low suction pressure or is it refrigerant flow?.