This episode of the HVAC school podcast is made possible because of the generous and ongoing support from our sponsors, testo carrier and rector seal, and i wanted to talk a little bit just real quickly about the test. O11. 5I. 159 tests o 159.

It is a wireless temperature clamp that has recently been proven to be even more accurate generally and I'm the test. Oh, you know test, Oh, doesn't doesn't say this and they don't they're, not telling me to say this. But but recently Jim Bergman did some testing with the test: o 115 s and some of the 605 eyes and other things with this measure, quick app and in so Jim. As you know, Jim's been on this podcast a lot.

He actually went to NIST NIS T, which is the National Institute of Standards testing, or something like that. I don't actually know you can with head stands for just should have looked that up beforehand, but you get the point they they are the the governing body that helps set the sets the standards for these sorts of things, and - and it was proven when compared to Extremely expensive pieces of test equipment that the test - Oh sensors, that they're using in their smart probes devices which, with the 115 s being an example of that, are extremely extremely accurate. And, like I mentioned you, can use those with the free test of smart probes. App or you can use them with the free measure, quick app that jim Bertman put out, and you can actually do some pretty cool things with those probes.

But i want to talk specifically about the test at 115 s, because today, we're gon na be talking a little bit about heat pumps, actually quite a bit about heat pumps and one thing that you'll notice, when you're checking a heat pump is there's some things that Are tricky to check specifically suction temperature, section line temperature on a heat on most heat pumps? Unless you have a wireless temperature probe, you know running that wire in there to get a connection on. The suction line can be really tricky, which is where the test o 115 eyes come in, really handy, they're, very reasonably priced. You can find them at true tech tools comm, as always, our offer code is get schooled for a great discount. Well, that is the test own 115, so I use them all the time they have actual thermistor sensors as opposed to thermocouples.

If you're used to those little brown or even some of the some of the clamps temperature clamps that are out there, most of them are thermocouples, not their misters and so they're not going to be as accurate in most cases as the tests own 115 s so Check them out test, Oh 115 eyes you can find them or any high quality products are sold or just go to true tech tools. Comm. This is the guy who gets excited whenever he learned something new about HVAC, which is every day, which means he is always a little too excited for a grown man, Brian or yeah. I'm gon na try to stay calm here.

Those you who know me well know that I am NOT actually an adult man, I'm just a child pent up in a chubby adult man's body. Once again, we have Carter Stanfield on the podcast Carter is one of my favourite educators out there and a really nice guy, and we were having a conversation which I'm gon na kind of recap in the podcast. I'm not gon na, not gon na give away. All the details yet, but we were having a conversation and he pointed out the importance of compression ratio and I've been wanting to have a compression ratio podcast for some time and so the day has finally come.

But this is not just a compression ratio podcasts! No! No, this is actually a pretty good look at heat pumps and why they are the way they are and some of the challenges with heat pumps, as specifically as it relates to setting a charge why the pressures are what they are and some of the other things About heat pumps, so I think it sort of has a dual purpose here. You can learn a lot about compression ratio and learn some things about heat pumps. Frankly, something about heat pumps that I I really never understood about the the infamous charge compensator on roads and rains, and so Carter reveals the details of that for us here we go Carter, Stanfield talkin compression ratio and heat pumps. Today, in the podcast we have Carter.

Stanfield, this is Carter's second time coming on the podcast he's an old pro. So thanks for coming on again Carter, I'm glad to do it so I'll, just kind of set the stage of how we decided to do this episode, because I wrote an article about and is actually a republish of an article that I wrote way back before. I even had any business writing articles, but I wrote it for my former employer before I started my own business about checking the charge, checking the system on heat pumps, because it was always a challenge in heating season once the outdoor temperature dropped below 65. What is the best way to check the charge on a heat pump, so I wrote an article on it just some of the tips things that some old timers taught me and some things that I've practiced over the years, because we work on a lot of heat Pumps here in Florida and after I published it, Carter commented on one of the Facebook posts about it.

That part of the challenge here has to do with compression ratio and compression ratio is something I understand. Generally speaking, but I know you understand it a lot better than me, so, let's start at the beginning, when it comes to compression ratio, what is it and why should it matter to the average technician? Well, let's start with a ratio is really just a comparison of two numbers, so with compression ratio we're comparing your discharge pressure to your suction pressure and I say: compare we mean divide so you're, dividing your absolute discharge pressure by your absolute suction pressure. In essence, you're really just seeing how much you're squeezing the gas. So if you have a compression ratio of say three to one, that means that your discharge pressure, your absolute discharge pressure, will be three times higher than your suction pressure.

Why it's important, if you think about it, if you're asking your compressor to do two things, we're asking it to move gas and we're also asking it to make this pressure? If you ask it to do more of one thing, then naturally it does a little bit less of the other. So if we ask to make more pressure difference, then we don't move as much gas and when you think about moving the gas, it may not be immediately obvious how much gas are moving, but to just give some quick and dirty numbers 14a you're, absorbing about a Hundred and twenty BTUs for every pound that evaporates so for a ton, you need to circulate a hundred pounds of that stuff, an hour you're doing a fair amount of work in terms of gas circulation. If you ask the compressor to make more pressure difference between the low side and the high side, then you can't move as much gas. Basically, you have sort of a fixed amount of work that you can do.

One way that helped me think about this, because only recently have I started to really get my head wrapped around it because there's two sides: the equation, obviously there's the head pressure and then there's also the suction pressure. But if you think about it in terms of on the suction side, the suction side is where the compressor is getting its refrigerant from, and so the compressor has a fixed volume in the head of that compressor. If you think of a piston compressing, there's a fixed tolerance in between the top of that piston and the cylinder head, and so that gap is a fixed volume but the actual mass. The actual number of atoms changes.

Depending on the density of that gas. And we know the density, we can see that by looking at the pressure of it, and so when you have something that has lower pressure you that volume remains the same, but that gas is lighter coming into it. When you have lighter gas, you are naturally going to tend to move less of it, there's less of it entering the head of that compressor. So is that a good way of thinking about that or is there a way that you would maybe amend that to make it more easier to understand? That's correct an analogy that I like to use like all analogies: it's not exactly right, but it gets you in the ballpark.

A lot of people understand about water pumps and head on water pumps versus gallons per minute moved, and how? If you ask the pump to move the water up 10 feet instead of 5 feet or 20 feet instead of 5 feet, that you get less water moved and all you know, pump curves and things will tell you that and the rule pumps like we work with, Like the condensate pumps usually have like a point at which they don't move anything, but anyway, most people understand that in water pumps and basically it's kind of the same, the compressor is just a vey per pump. The main difference is that, unlike water, the gas can squeeze so that changes the dynamics just a little bit, and so, if you think about it, in terms of compression ratio, is taking into account the head that you're working against the amount of pressure that the compressor Has to work against as well as the actual mass of the refrigerant coming in, and so it's taking that differential and the greater the differential. The more that compressor has to increase the pressure of that refrigerant. The less refrigerant is going to move, which is essentially what you said earlier, but you can think about it on both sides of the equation.

So if you have a system, that's working perfectly good on a 75 degree, indoor temperature and a 90 degree outdoor day and it's just humming along beautifully and you walk up to it and block the condenser off to it. And you drive that head pressure up, you're going to move less refrigerant because we're forcing that compressor to work against a higher head pressure and in the same way. If, on that same unit, you go inside and you reduce the indoor load by blocking off the return. Air grill.

Well then, you're going to reduce the amount of heat. That's entering the refrigerant and you're, also going to reduce the density of the refrigerant. That's entering you're dropping the suction pressure, and that would also increase your compression ratio, which would reduce the amount of refrigerant that you're moving, and so you can think about it either way, but the compression ratio just takes into account both sides of the equation. Now something mentioned the effects of both the high side and the low side.

Something a lot of people don't realize is that the low side changes in your low side pressure actually affect your compression ratio, a lot more quickly than changes in your high side pressure. So, for example, if your low side goes from 40 to 20, that's a much larger percentage change than if you go say from 250 to 270. So if you work through just a little bit of math, you can see that stopped up filters and blocked coils and things have a big effect on the compression ratio, not that pluged condensers, don't but evaporator will mess up your compression ratio a lot faster than a Condenser will yep two things that I want to mention quickly before we move on and get anybody confused. You made a really important distinction that it's the difference between discharge in suctions, so it's the refrigerant right before it goes into that compressor and the refrigerant right after it goes out of the compressor.

So you can't compare suction pressure to say liquid pressure and get a true compression ratio. Is that correct? That depends a lot on the system and how much pressure difference areas between your discharge and your liquid, but because you've got a lot of piping and sometimes some components. Besides the condenser in between your discharge and your liquid, you could get some funny things there with like a typical residential air conditioning system. There, probably is not a lot of difference when you're discharging your liquid, but you get to say a commercial refrigeration rack system and there could be a big difference.

So you had also mentioned the absolute pressure. So when you say absolute pressure, how is that different than gage pressure with your standard gages, if you have them open to the air? The gauge reads: zero: every pressure. Reading we take with those gauges we're reading how much pressure we have above atmospheric pressure, but the truth is at atmosphere. We really don't have zero.

We have almost 15 somewhere around 14 point 7. So absolute pressure takes that into account. So if you were to use a set of gauges calibrated to absolute pressure when you unscrewed your hose before you even connected it to anything, you'd be reading about 15 pounds. And then, when you read your refrigerant pressure, it would be about 15 pounds higher than what we typically see in our gauges today.

So the conversion is pretty simple. You just add your atmospheric pressure to each of your suction and discharge pressures for most purposes, 15 works. Pretty well, if you want to be really accurate, you can actually measure your barometric pressure or look it up for that day and add to it because it can vary both like you mentioned barometric pressure. It varies day to day, even in certain places, but then it's a you're in way up in the mountains.

Then it would be slightly lower as well. So again, this is really really getting really fine and detailed here, but that's why they have that, because, when you're looking at it from an engineering standpoint, you do want it to be very accurate and detailed. The point is when you're calculating compression ratio, you don't just take the pressures that you read and divide the suction into the head pressure. You have to first add approximately 14.7 to each that's a c-level number in order to get that exact number one before you do.

Your division and then it could make a pretty big difference in terms of your actual answer, if you forget to do it whatsoever for sure okay. So now, let's move into some of the circumstances in which it matters, and so let's focus first on what we were originally discussing, which is in heat pumps, and why the dynamic changes in compression ratio can really affect the operation of the system. One of the things that makes working with heat pumps, in particular heat pump charging in the heating SIG's in a challenge, is that the amount of refrigerant moved varies quite a bit depending on the conditions, so the amount of refrigerant moved I'll pull up this little chart. I'm looking at I'm looking at a Goodman performance chart of a unit that has an H SPF of nine.

So this is not a super high efficiency unit. It's just sort of a middle-of-the-road sort of unit and ton-and-a-half unit, so at 47 degrees outside is capacity, is 18 thousand BTUs, which is pretty much exactly the same as the cooling capacity at ninety five. At ten degrees, however, his capacity is only nine thousand four hundred BTUs, so pretty much half of what it is at forty seven and the reason is because at ten my evaporator pressure and temperature going to be much lower so that the compression ratio is higher. The compressor just can't move as much gas, so you're moving about half as much refrigerant when it's ten degrees outside as you are when it's forty seven outside for charging purposes where that presents a problem is, if I'm trying to charge it in heating and it's ten Degrees outside once I get to say if I was going from absolutely nothing once I get half the charge in there, and my pressures are actually gon na be correct because I'm moving all the refrigerant that it can move at that point, and I still, though, I'm Only got half the charge in the other half the charge is basically sitting somewhere when the unit's charged up right.

But it's hard to tell if I've got that other half of charge sitting in my accumulator or in the coil somewhere and that's why a lot of manufacturers don't particularly like you trying to add charge to it on the heating cycle very interesting yeah, and I remember Even to this day, I don't completely understand how this component works, but I remember back in the day we used to have a lot of trouble for whatever reason, with Rheem heat pumps in heat mode. They would have a lot of issue where you know they would go out on high head and I think a lot of it had to do with the way the ductwork was installed and the air handler. So they were running low, airflow and a lot of cases, but they used to have a little component called a charge compensator that they would install in there, and that was the general ideas it kind of gave a place for that. I was almost like a little mini receiver, where it gave a place for that additional refrigerant to hang out whenever it was in the heating mode.

Have you ever seen something like that yeah and I can explain both what it does and why Rheem in particular had a problem with that? Oh great, please do. This is something I actually do not know the answer to, and it's been probably eight years since that seen one those indoor coils that they had may still have. But look like an M or a W small diameter single row pipe going up and down. They don't have very much volume in them and their heat pump.

Blower coils. If you look at heat pump, blower coils that they made they had flanges for your ductwork, but they weren't on the outside of the blower. They were kind of in the middle and it had a big orange sticker on them and it said fold this up. A lot of people didn't do that, though they saved him an inch and shipping.

Basically, it's what it did, but if you didn't fold it up, it was blocking the air flow and also told you in the instructions that the ductwork was to connect to those flanges which were kind of in the middle of the unit not only outside. But everybody doing what they always do put their plenums on the outside and that blower they save space by cutting off the straight part of the blower. Now, when you look at a centrifugal blower, it kind of slings, the air in all directions and then the straight part coming off the blower straightens it out and gives it direction. If you don't have that straight part, then the blower doesn't perform as well.

So if you don't hook the ductwork to those flanges that they gave you there's no straight part to the blower and a blower doesn't move as much air. So then, what happens when you go to check the charge in the cooling season and you're not moving as much air? Well, people would fix that air problem by overcharging it to try to bring the suction pressures up and keep it from freezing up. Well. Not only have too much frigid in it when it got to heating.

Those coils couldn't hold all that extra refrigerant, so it would be popping the pressure switch all the time so yeah. I knew people that would every summer every spring really go out and add charge and then every fall got and take it back out, and it was because of an installation error. It's funny, because I have a house in mind. I was probably 19 years old and I had to go back to it a couple times and I can picture the house.

I can picture the unit and I was running into this exact problem that you're identifying and sure enough. I mean at the time you're thinking. Well, if you attach the duct on the outside of the unit, that's better because you're giving it more flow right, I mean that's the thinking that my young brain had, but now that you're bringing this up. It's just bringing back all these memories, but very interesting stuff.

There is a way to put this plenum on the outside if you just absolutely have to do that, and you put like a 1 foot collar on those flanges. So what you do when you do that, is you effectively put the rest of the blower on there? The part that straightens it out, then, when you put your plenum on the outside, you have to make sure that it's long enough that any takeoffs are a good ways away from the end of that collar that you got inside there. It all came about because they did some unusual things with their heat pump blowers and they were clever, but they were different and people a lot of times in history aren't really too good with different, especially if it requires reading and following a set of instructions. So that's why they had air flow issues.

Now you could run into that same problem with anybody see not just those old dream ones, but because they did some dings that were kind of different. They gave some people some headaches the charge compensator. What happens with that? It's a little bit like a liquid receiver. If I can put a plug, it's actually in the book in the heat pump section, the only thing is it's different and illiquid receiver.

You have an in and an out for your liquid and a charge compensator the in and the out of just one pipe. You have one pipe that so two that cylinder that goes to the liquid line and then the gas line that goes to the outdoor coil runs through the charge compensator. So it's not opened up to it. It just literally runs through it and what happens is when you're in the heating cycle that gas line is cold because it's basically the suction line, creates a low-pressure in that tank and it sucks any liquid, especially any extra liquid out of the liquid line and into That tank, so it gives a liquid a place to sit when it's running in heat and then, when it runs in cooling, the gas line is now a discharge line.

It heats up, creates pressure and forces that liquids it's stored in that tank to go back into the liquid line very interesting in retrospect. At the time I was just kind of like probably like most techs are nowadays with a lot of things it's like. Well, I don't know when holds charge somehow it's magic, yeah kind of an interesting thing. I've only seen that style of charge compensator on reims and Rhodes, trains and American standards also have charge compensators, but the ones I've seen are really just kind of a large filter.

Dryer shell, with no dryer core in it. If you work on ductless systems, then you know they can be challenging to maintain and if you don't work on ductless systems and you're, just gon na have to take my word for it. The the fin spacing on the evaporator coils are very tight and even actually the condenser coil fin spacing is also tight, and then they also have these blower wheels that are really long and the cups on them are just tiny and they tend to gather up. Don't over time and they just stop working efficiently if they get dirty at all, they get any significant grime on them.

They stop working properly. So the challenge is with ductless is how do you clean them because often ductless systems aren't? You know they're mounted up on walls in places that you can't get water all over the place. So how do you clean them properly and one way you can do it is you can pull them all apart? You can pull the blower wheels out, but even then, if you do that, you still have to worry about how you clean the evaporator coils. So what do you do? Pull the whole air handler off the wall? Well, never fear.

Rector seal makes the dissolve kit and it's the word dissolved without the e on the end, as is very popular nowadays and to omit any vowel, so it's dissolved and they make its a kit. It's also a cleaner, and so they have a cleaning solution that you can spray on the evaporator, coil and blower wheel. But then it also has this bib that mounts underneath the air handler or fan coil whatever you want to call it, and you can actually use a wand to clean that off and it all funnels down into a bucket and what's nice about the kid. Is that because everything fits inside the bucket, so you just keep the bucket on your truck.

You've got the bib. You've got the little drain that drains down into the bucket you've got the cleaner. You've got everything all there in one place. So it's a pretty cool kit check it out.

It is the erector seal dissolve kit. Also, if you work on ductless, one thing that a lot of people struggle with is this idea of testing performance on a ductless system because checking the charge is really tough. On ductless I mean you can tell if the things flat but other than that, it's tricky because there's so many moving parts, but what you can do pretty easily on most ductless systems is you can get a a chart that shows you the different CFM output for The different stages of operation: let's talk about the two different sides of the equation, because I think we are affected on both sides when it comes to high compression ratio in many systems because of the config Eurasian, because now your condenser coils inside and then your evaporator Coils outside and so talk about that a little bit some of the challenges that are generally faced. One thing that's interesting about this: if you think about the relative size of the coils in a standard air conditioning system, you've got more coil surface area on your condenser than you do your evaporator.

Now, when we reverse that that means that our coil surfaces are kind of opposite what we're used to when were in air conditioning and when it's cold outside that serves us well, because that extra surface area, that's now on our evaporator, helps us pick up the heat That we need, and then the smaller surface area on the condenser helps kind of pump your pressures up and get your keeper temperatures warm, that's sort of all on purpose and it works reasonably well at fairly low temperatures trying to help us keep the compression ratio down Somewhat but as it gets colder there's only so much you can do when it's like you've got five degree, air or zero Degree air going across your coil, there's only so much heat to gain, no matter how big your coil is. So the difference between your suction pressure and your discharge pressure increases and that's when your compression ratio goes up and the amount of your circulating goes down and, like you mentioned it's the suction side, that is more easily impacts the compression ratio, but then, and in the Fact that indoor air flow problems are so persistent in our industry and now, when you have indoor air flow problems, dirty filters, those sorts of things that also can serve to drive up the head pressure in some cases significantly because you're already sort of fighting the Battle Of having less surface area inside and smaller coils, and then you would normally and that can cause you to kind of be working against it in both directions. What can happen there, like with a airflow issue? Is that not only do you get the high compression ratio, which of course hurts your capacity, but it hurts your compressor because now you're not moving as much gas as it was originally designed to move, and so the compressor starts heating up and that also confused people. Somehow the compressors actually get hotter and work harder at cold temperatures than at hot temperatures.

So, as a general rule, the compressor will be operating cooler and be happier when it's 95 outside your air conditioning. Then, when it's 5 outside and you're hating, you make a really good observation there, and that applies ties directly into another place, that we see issues with compression ratios and that's in refrigeration, because on a refrigeration, compressors, let's say you're working on a rack or something that Compressor is much more concerned about the compressor, though it's a compressor, it's inanimate object. It's not concerned about anything, but it's much more damaged by high compression ratios than it is by the actual temperature of the refrigerant coming back. You know the idea would be well if you have a really really cold, evaporator, coil and you've got a 10 degree superheat or whatever the case may be.

Then you've got cold refrigerant coming back. That should cool that compressor, but in actuality it would be happier if you had higher load and the gas was actually denser coming back. That would actually do a better job of cooling that compressor, which is counterintuitive to a lot of us. Well.

The other thing is that when you get a hermetic compressor or a semi, hermetic compressor, really you're buying two things: you're buying a compressor and you're buying a motor, that's matched to that compressor and the match of the motor and the compressor depends very much what you're Going to ask it to do so, a compressor this design for a freezer, for example, really needs a different match than a compressor of this design for an air conditioner and that's another challenge with heat pumps, because you really are kind of asking it to do both Things that was one of the challenges in designing reliable heat pumps is getting a compressor that could operate happily across those wide evaporator temperature ranges well, and that's one of the real benefits to these kind of new generations of inverter driven compressors is that now, as your Compression ratio naturally starts to increase and that compressor is naturally no longer capable of maintaining the capacity. The modern inverter driven compressor, it's a scroll or rotary compressor - can actually increase its RPMs in order to continue to produce a decent amount of capacity, even at very, very low temperatures in comparison to its single speed counterparts, which is a whole nother conversation about the longevity Or something efficacy of some of that from a serviceability standpoint, but from just a raw ability to produce the design BTUs, there's some clear advantages there, oh sure, yeah, that's really nice! So let's talk quickly about how in refrigeration you can kind of have the opposite problem. In a heat pump, you have this highly variable: evaporator temperature, but in refrigeration you can have very highly variable condensing and some of the strategies that are used there, but that can also have an effect on compression ratio. Correct, oh sure, so one of the obvious differences with a commercial refrigeration system and a residential air conditioning system is that you have to operate year-round.

So you can have a condenser operating in fairly cold weather and you've got really a couple of things you have to do. One is most your metering devices or most your common standard metering devices require a minimum pressure difference in order to operate so a lot of systems have head pressure controls and the purpose of the head pressure control is to have a minimum head pressure, no matter how Cold, it is outside so that your expansion valve can keep operating when you start forcing your head pressure up on purpose, so that your metering device works right. Well, there's an energy hit there in that you're increasing your compression ratio, you wouldn't you wouldn't have to so a floating head pressure system basically, but you have to do to have that type of system as first you have to have a better metering device. So if you have a metering device that doesn't require a minimum pressure difference or requires a much lower minimum pressure difference, then you can let the head pressure go a lot lower, meaning that I can have a lower head pressure, a lower compression ratio and use less Energy to do the same amount of cooling well and also in having that lower compression ratio, and not only you use less energy, but you also have much happier compressors clearly because it like we mentioned before your compressor is happiest when it has a lower compression ratio.

In my experience with compression ratios, they can vary wildly on like key pumps like we just mentioned. If you have a heat pump where the evaporator temperatures is dropping, because, obviously, from a very practical standpoint, your evaporator temperature has to and minimum be below your outdoor temperature. Otherwise, you're not moving any Heat, and so as that evaporator temperature drops, your compression ratios are going to skyrocket, but on the air-conditioning side, a modern high-efficiency system may have a compressor, that's designed for say a two point: seven compression ratio, two point: six in that range And then you go into heat mode, where your compression ratio could be five: six, seven, eight nine in some cases, and obviously that's going to reduce the output of that compressor. Unless that compressor has some way of increasing its rpm or increasing its output.

And that just shows you why it is so hard or why manufacturers a lot of times shy away from wanting you to add refrigerant, wanting you to make charge adjustments in the heating season, because it's very challenging as those conditions change as the outdoor temperature changes. But then also another thing we haven't talked about is that you may have a system that doesn't have visible frost like a sheet of ice on it, but it may have some frost and any amount of frost is going to inhibit the ability for that coil to Transfer heat, which is then also going to have an effect true to some extent. You have this problem also in air conditioning, but it's not as dramatic if you look at, for example, superheat charging charts with fixed restrictions, but they're really telling you, when you see super heats in the high 20s and low 30s. What they're really telling you is the system is not at full capacity at that condition because of the lower head pressure, so that means, in effect, you have the same situation where you're not moving as much refrigerant, because the changed compression ratios but they're they do actually Go ahead and give you a guide for charging, it's just not as dramatic a change as you have in the heating cycle.

So speaking of awesome tools that I really believe in I've always been a fan of the Bacharach leak detectors, and so I've been a user of the H 10 way back all the way to before it was Bacharach when it was Yokogawa GE. The H 10 leak detector, which became the H 10 G, which is now the H 10 Pro, but we're not talking about that leak detector. We are talking about the Mac Daddy. Basically, the most accurate high quality leak detector made on planet earth.

As far as a portable leak detector, when you can actually carry around - and that is the Bacharach PGM IR - and you may ask yourself - you may say well what is special about the PG Mir and I'm here to tell you it actually has a display on it. So an LCD display that shows you the parts-per-million of a particular refrigerant when you're measuring. That really is the most awesome thing about it is you can actually, as you're, getting closer to a leak source, you can actually track the parts-per-million of a particular refrigerant type, and you may say: well what you mean is is an HF C or CFC. No, no and a specific refrigerant so like you can put in r410a or r22, or anything that you want are 407 C whatever you, whatever type of refrigerant you're working on you can put in that specific refrigerant in the PG Mir, will tell you with incredible accuracy: How many parts per million there are in that particular vicinity, which means that you can actually start to sense a leak when you walk into a building.

In many cases you can actually like walk into a ste convenience store into a house and you'll start to pick up refrigerant if there's a leak in an evaporator coil, and so you can actually trace that thing down to the to the source and we tried it. We've used it in a couple different applications, and it was just incredible. It also has just incredible resolution. So when you talk about accuracy or resolution, it can read down to one part per million with almost every refrigerant that exists out there today, and so it's just a credible level of accuracy and gives you that readout on the display and you can actually select the Refrigerant yourself, I'll tell you it's not an inexpensive leak detector because it's a super high quality leak detector.

But if you work in large commercial, you work in grocery store applications or you want to have just literally the best leak detector. That's out there. I mean it saved us. We had a job that we were going to have to do a lion, isolation test to prove that the leak was an alliance set.

But with the P G Mir, we could pinpoint exactly the concentrations of refrigerant down a line chase and we actually did a video of that. If you go to true tech tools and look at their YouTube channel, you can you can check that out and see that video of us using and demonstrating the P G Mir and you can get the PG Mir from true tech tools. So you go to true tech tools: comm you can get an excellent discount by using our offer code get schooled at checkout also if to find out more. This is what I'm gon na suggest to you to find out more so you're gon na wan na you're gon na want to pause this.

So you can get a pen to write with let's pause it real quick, go to my Mac, Iraq comm, which is BAC har. Ach my back Iraq, comm /h VA CR school. So that's my Bacharach comm /h IVAC our school to find out more alright to wrap this up. Then what advice would you give the technician out there who works on a lot of heat pumps and they're in a market where they are below 65 degrees and a lot of circumstances, and there is obviously pressure in the industry to follow manufacturer specs and of course I say the same thing follow manufacturer specifications, but in a lot of cases, you're in the field where manufacturer specifications may not always be easily found, or you may be working on older equipment and so for somebody who walks up to a system and they're they just Do a simple repair: let's say they replace a capacitor, but they want to verify this heat pumps operation.

They want to make sure that it's doing what it's supposed to do. What suggestion would you give? Well, it is a tough one. I do always start with whatever the manufacturer says and sometimes you're right. What the manufacturer says, isn't reasonable for your situation.

I can remember years ago, when a manufacturer was saying you should always just wait. The charge in I said. Well, that's no good! Unless I'm going from scratch - and I certainly don't want to go out and pull it all out and pull the vacuum and wait in just to make sure I'm right and that's not reasonable. This second thing that they offered was temperature difference just measuring what the heat pump is able to do, and, of course, there's a big gotcha.

There is that you can't do anything with your temperature difference unless you also measure your air flow and know what your airflow is. But if you have standard airflow, then you can actually from your temperature difference, calculate how much heating you're accomplishing and if you look at the manufacturer's, extended capacity charts. You can kind of work that back and see if it's doing what it's supposed to do so, for example, if you're looking at this chart, Goodman actually has some really good, extended capacity charts, and you can thing I like about them. Is you can download them easily? You don't have to have a password or anything, but if you look at their extended capacity charts you can see from at the outdoor temperature operating at how many BTUs it should be able to produce.

And then you just work that backwards with your air formula. To figure out what kind of temperature drop that would give you or temperature rise and measure your temperature rise, preferably close to the coil, not at the return and supply grills, because there's a whole other host issues. You can come in with that, preferably close to the coil, and if you got a temperature rise close to what the manufacturers saying should have and you're probably doing what you're gon na do that calculation actually is a little easier and heat mode than it is in Cooling mode because you're not having to deal with latent heat. Obviously it's all gon na be sensible, so that's fairly easy and actually another thing that's getting easier than it used to be.

Is you have a much better chance of hitting close to your specified airflow? Now, in the modern era of the ECM and the x13, because they are a little more tolerant to high-ish static pressure, if you look at most of the fan charts until you get up to point eight point: nine, it's usually going to produce the designed airflow, pretty Close to it, so that makes it a little easier than some of the older ones. But again you still have to have a situation where you've got a clean, blower wheel. Obviously it is just all the obvious things you got: ta have the proper sized blower wheel. It's got to be clean.

You want to do a good visual inspection of the unit, but I do like that. I, like that method and I'm starting to use that more and more even on ductless systems. You know that's another segment of the industry that it's very difficult to verify system operation. On the refrigerant side, I talked a lot about the test: 6:05 eyes, they're just little digital thermal hygrometers that are very accurate.

You can use two of those and very quickly confirm how many BTUs a system is delivering as long as you can it with at least reasonable accuracy and figure out what the airflow is and, like I said, with extra teens and ECMs. That is a little easier than it used to be, at least that's true. With a cm system, you can feel pretty comfortable with the air flow yeah which just for those of you who are thinking well, why would that make any difference on the old PSC motors? The static pressure changes all the way through the entire spectrum, so all the way from your static pressure being lower than 0.5. All the way up to 0.9 there's gon na be a huge change in air flow, which you can measure static pressure, and that is something that you should do, but then throw in things like well what if the coil is a little bit dirty or what? If somebody put in a different aftermarket PSC and you didn't notice it, it just makes things a lot more challenging where it's very easy to identify.

Whether or not this system has a factory extra, teen or ECM, and it makes that job a little easier. Now I've been experimenting with that quite a bit lately and it is pretty accurate using two 6:05 eyes and then just Reno relying on the fan, charts and most of those are pretty easy to pull up. Nowadays, most manufacturers, you can get those online and you know a couple minutes anyway. Is there anything else that I'm missing on this topic Carter? Not that comes to mind immediately.

I mean this is something you could talk about for days, especially when you start talking about how to check heat pumps in the heating season. You can't really get very much agreement between manufacturers much less between technicians, so it is a challenging job. If your technician out there and working on a bunch of different equipment and you're getting really kind of a different story from different manufacturers, if you just understand why they have the opinion that they do, it makes it a little easier to take. For example, I didn't really like the idea they're saying we can't give you a charging chart for heating and once I understood why they had a problem with that, it was a little easier to understand sort of their attitude on it right, a lot of variables, the More variable conditions are the more difficult it is to give a set answer right because there's so many different moving parts and when you're in service circumstances you're just dealing with, is it overcharged or is it undercharged its? Is it slightly overcharged with a dirty blower wheel and a little frost on the outdoor coil? You know there's a lot of different things that could be going on all at once.

They could give you even the idea that it's okay, when maybe there is a problem but, like you mentioned verifying actual delivered capacity, is always a good go-to. When all else fails - and I think that's good advice - I am glad to find out that the fundamentals of HVAC are on the book that you co-author does talk about charge compensators. I must have missed that part there and my readings. No.

Yes in there was a picture show on both of cooling and hazing cycle, how it works Morini, so for no other reason than that go look for that. You can find it on Amazon or a lot of online booksellers. You'll find it fundamentals of H, VCR, co-authored by Carter Stanfield. So thank you again for your time Carter and I think it's very valuable, and I appreciate all that you do for the trade.

Oh. Thank you all right. So we've come to the end. We've come to the end of this episode of HVAC school, but I was just clicking around my computer.

Let me click back to this right here and look at it. Yeah fundamentals of HVAC are by Carter. Stanfield and David scavs is available on several different sites, but you can find it on Amazon. If you go to Amazon, you can find it there as well as some other HVAC specific bookstores down on the web.

But if you just just look it up by name just search it by name and you will you'll find it right there now, they suggest looking for its fundamentals of HVAC, our by Carter, Stanfield and David Skaggs, and, like you mentioned, he does talk in there about Charge compensator so silly on me for not for not noticing that, but it's a something that I've seen in the field and never really took the time to understand. So Thank You Carter for pointing that out to me and really just doing a great job on this episode. I thought it was really helpful, very, very applicable stuff that he brought to the table. As always, you can find out more about all the podcast in the blue-collar roots Network.

By going to blue-collar roots comm, that's blue-collar roots comm. We have the tool pros: podcast service business, mastery, hvac, building science, hvac shoptalk, the tradesmen and several others that you can find by going to blue-collar roots comm, but once you find them there don't stop there. No! No go to your podcast player of choice on your phone, which is the other thing that I suggest that you do for HVAC school. If you, if you care about hearing it regularly and subscribe to it there, every every different way of listening to a podcast, every application out there, you should be able to find all of the all of your favorite HVAC and trade specific podcast in the blue color Roots Network, whether that is the Google Play Store or whether it's the stitcher app or whether it is the podcast app directly on your iPhone.

You should be able to find them all those places. In fact, you should even be able to walk up to an Amazon, Alexa and say Alexa play the HVAC school podcast. But if my experience is any guide, it won't actually work cuz. I haven't been able to make that work yet.

But theoretically, that should also happen. If you have not signed up for the daily tech tip, I would ask you to go to HVAC our school comm sign up for that I've been doing them a little less than Bailey the last a little bit. I've had a lot of things going on, but I've been doing them about three times a week with new, with new content and recycling some old stuff. Actually, today, I'm gon na be publishing one on keeping warm through the cold winter, because this is the first cold snap in Florida and I'm literally freezing my buns off, because in Florida we are just not used to anything below 40 degrees is a total total carnage.

I had a little frost moment Sheila, I absolutely did not know what to do with it. It was freaky so anyway, in Florida you know we give a little bit of cold weather, we got ta stay inside and you know we realized my wife and I were talking about some movies we could watch. I realized I never watched the movie et before at least not as an adult. I saw it as a kid, but we never.

We never watched again as an adult. I thought. Well, you know, let's, let's watch it kind of fer nostalgic reasons and put it on the kids are watching it, and one of my daughters looks and says dad dad what's et short for Michael, that's obvious is because he has little legs. Alright, we'll see you next time on hvac school.