All right, so today we are going to talk about heat pumps. I just uh pulled up the article on home charging just as a reference i didn't make like a powerpoint presentation or anything, but we're just gon na have the first little bit we'll just kind of talk through it and then we'll actually go through some things. On the uh on the equipment really actively moving my hands is there a place? I can find this article to help you follow along. You sure can it's on hvacrschool.com or the hvac school podcast, htc's, glass, sorry, okay, that was rough here, let's go uh and you just type in just pump charging or keep mode charging.

I guess as well yeah. So i'm not going to read the entire really long. Um url, that would be annoying. I actually wrote most of this article most of what this is back.

When i made a a little training handbook in my del air days, just went ahead and said it and uh. So this is actually a picture of the old carrier pump that i had at my house. Minnie haha. Isn't everybody excited about that yeah? Absolutely so, yeah really exciting um.

So a lot of the rules of thumb still remain: uh heat pump, heat mode, heat pump, charging and testing. There are a lot of rules of thumb and uh they're, not like crazy, accurate but, generally speaking, our heating season is so short that you're not expected to. Like you know, make huge adjustments generally, but you want to make sure that the equipment's running properly, if you work in you, know if you're out there in youtube land and you work on equipment where you have really long heating seasons, then, generally speaking, you're going to Rely more on weighing in laying out that kind of thing: it's very cold because it is challenging um. There are some techniques you can use to be pretty accurate, but they're pretty in-depth and we'll talk about that.

But let's start with just connecting to a heat pump in heat mode. This is one of my favorite examples of the system, that's kind of interesting. To hook. Up to so, we've got our our heat mode port, which is always suction or common.

Suction is what we call it, so that is connected where, where is that connected in the system? It's connected, it's not on the reversing valve, it's between the reversing valve and the compressor and the suction mount. So if we look inside and we'll do this in a little bit, if you look inside a unit, the reversing valve the top and the bottom, so the tops by itself - usually it's a discharge line, smaller line and then the bottom in the center is the suction Line those connect directly to the compressor and then it kind of flip-flops those depending on whether you're running in heat or pool, which basically defines whether or not your indoor coil is an evaporator or a condenser. Whether or not your outdoor coil is evaporated so, whether it's absorbing heat or ejecting heat, obviously in cooling mode, we want to absorb heat from the inside and reject it outside in heating mode. We want to absorb heat from the outside and injected inside right.

That's the idea, when you're running a heat pump in heat mode, you want to connect your low side to that port. Now it used to be when you were using analog gauges, that it was kind of a big deal if you accidentally hooked your suction gauge to the high side, because it would pave your gauge and ruin it nowadays with digital gauges and probes. They don't really care like it's not going to hurt the probe or the manifold if you connect to the wrong port because you're not pegging a needle but obviously you're going to get in incorrectly go ahead. Burke um! Why does it say at the very end of the old manifold pages like if you had it hooked up on that side? It would just throw your dial into where it says: yep uh, that is actually a real question uh, and this is the source of many inappropriate jokes on facebook groups, not hvac school, because we don't make those kind of jokes i'm.

I know it is really true. So uh we'll put it up in the video, so you can see a picture of what the old suction cage looks like and it does it has this spot at the end. That says, and all that means is, is that when it gets to that level, it actually has like a spring force or some opposing force that keeps it from pegging that needle and breaking it when it over pressurizes. So it goes to a point, and then it actually has something that kind of prevents it from breaking itself.

That makes sense so so, in that case means like to um to push against uh to and hit it. That's really what that word means. It means inhibited or to enhance, i just thought. Maybe it was like the manufacturers telling you.

You were really stupid, we're not making that joke. You already just said that it's not a joke. Did you actually thought that? Actually, oh you thought that's what it was. Oh, you really thought that yeah when i first started, i i thought that yes, whereas it used to be a really big deal, it still matters because you're going to get wrong readings, if you don't, but you want to connect what was your suction gauge? You know your suction gauge would generally be hooked to your suction line and heat pumps.

They actually don't call that a suction line. Technically, you know what this line is called technically, when your system is a heat pump. What's it called a vehicle, the vapor line and jim berman was the one who first told me that and made a real big fuss about it um. I would just call it the discharge line when it was in heat mode and the suction line was a cooling mode, but he insisted it's the vapor line, and that is an accurate name, and why is that an accurate name? We call it the vapor line, eli.

Why is it an accurate name on a heat pump to call the large line in between the condenser and the air handles? The vapor line always has a vapor, and it's not always a suction line, exactly because the discharge line is fully vaped for the suction line's. Fully vapor discharge lines: high pressure, high temperature, vapor suction line is low pressure, low temperature vapor, but they're both vapor vapor in the compressor vapor out of the compressor right. So that's what we would call the vapor line and the direction of flow changes same thing with the liquid line, the direction the flow changes in the liquid line, but the liquid line always stays the liquid line right now, when i first did this, there was a Lot of people who got cranky about this because i said in cool mode, i also said hook here i probably should have said connect. You know people can get the wrong idea, but i said in heat mode hook here and here suction here discharge there.

So people would get upset because they'd say well. Why can't you just leave your high side gauge connected here? Why can't you because it's the liquid line either way, so why can i not just leave my high side gauge connected here on this system? You know why, eric on this unit, it's the expansion line exactly on this unit, it's the expanse line. It says it right here: expansion line and heat. The reason being is because the metering device in heat mode is located right here, that's the metering device.

When you get past the metering device, you either call that the expansion line or the evaporator right - that's it becomes the evaporator. So whereas right here this is high pressure, that's not where my port is right. Here is where my port is, and that's no longer high pressure. Now, it's not it's also not completely low pressure either.

If you ever measure it you'll notice it's higher than your suction pressure, because it hasn't had a chance to fully expand yet, but it's certainly not high side anymore. Isn't that more of a carrier thing, though, to have the meter invited outside it's very much carrier thing? It's going away, and so it's maybe kind of an arcane but you'll still see a lot of them out there, like that. If you're working on most brands, where the metering device is inside, whether it's a txv or an orifice or whatever it is well, then you could leave your high set connect there. In fact, i would recommend that you do because now you can measure sub cooling right.

You can't measure sub cooling accurately when you connect to a discharge line, because the pressure on the discharge line, the pressure on the liquid line are different right, so in heat mode, they're different. How do we know if that's one of the medium devices on the system? So it just takes some system knowledge. Obviously you know if you've ever installed a carrier system. You know that you're putting a piston in here whether or not you have the old tool.

This is an r22 system. This is the flare fitting. This is what they used to use, and so when, when they came shipped, they would have a cap there and they'd have a little bag with a piston, and you put it in or it's behind the behind the cap, whereas nowadays with r410a, they use a chat. Like fitting with a teflon o-ring, so just experience knowing that so, let's say because i'm used to working on goodness exactly or trains um systems of those.

We didn't have a lot of carriers where i was located. So if i were to walk up to one of these, how would i know that i need to connect at this line versus the other versus the other line based on the system itself for the universe? So again i don't know that there is anyone other than carrier who does it this way? Okay, does anyone else know? I think it's only cured so goodman will use a heat mode, piston, sometimes uh, but it's inside the cap, um lennox is pretty much going to use always txt. Even modern carrier systems are going to a lot more txps in heat mode inside the unit. So that's going to be self-evident at that point, but you're always sort of looking for the easiest way to think of it is there's always a metering device somewhere so identify where it is.

And if you look inside this unit and there's no txv in there and it's a heat pump, that kind of leaves right here at that point you know and that that is right where it is so it's sort of process of elimination. It's actually an interesting thing in this: i'm going to go up on a little a little side note here, because it's a similar topic. If you work on a lot of rgus uh kind of these small medium size, rooftop units you're, going to notice that you trace down your liquid line and all of a sudden, it goes into a header and then just go straight into the evaporator coil. There's, like you, don't see a metering device and i remember seeing that like what on earth is going on, but actually there's all these little header crimps and those header crimps act as the metering device, because what is a metering device? How would you define? I mean your device joel controls, the pressure requester yeah it does.

It controls the amount of pressure uh, it's the pressure decreaser, so it can't raise the pressure. All i can do is decrease the pressure. It's just a question of by how much right, if it's a fixed surface, whether it's a header, crimp or a capillary tube or a piston um, it's only doing it just with an orifice right, and so it's a pressure drop across that orifice. That's proportional to the pressure differential, it's really pressure and pressure out very simple.

So that's what you're, basically looking for, where is the material device, and if you don't find it anywhere else, it's obviously going to be there, but this is just sort of. In my opinion, this is sort of a poor design, because this is not a valuable measurement. In heat mode i mean maybe it could be if you had a chart to reference or something, but we don't so um, it's not a valuable. It's not a valuable uh measurement.

So you've got to move suction side here, high side here pretty much every other system. You can just leave your high side on the liquid line and they connect to common sections and the common sections located a lot of different places like train, because they're generally, their uh reversing valves, are in the uh in between the coil and the panel, which is A really nice place to put a reversing valve you can actually just attach right above and below the reversing valve, so it becomes more obvious. It is kind of a nice. That's one thing that trained us that i that i do like go ahead.

I was going to say if you're working on this equipment a lot is there any kind of rule of thumb pressure drop across the evaporator, so you can take a discharge measurement, take a liquid line temperature and try to extrapolate sub cooling. Not that i'm aware of i'm sure, if you did those measurements enough, you probably could jim bergman claims. If i remember correctly, 10 to 15. Psi is a standard pressure drop across a condenser coil, a residential condenser core.

So that's the difference between your discharge. Your typical discharge pressure and your typical liquid pressure, but that's not going to hold true for your indoor coil and again, when we're talking about heat pumps, it gets the language becomes confusing, because we can't just call the indoor coil out of operatic well anymore. You know it's the artist formerly known as the evaporative oil. Now it's the condenser, so we just i that's why i tend to refer to them as the indoor coil and the outdoor coil and they're a condenser or evaporator, depending on whether or not you're in heating season or cooling season, all right cool, any questions about that.

Any comments anything you want to add so connecting in the right spot paying attention to where your meeting device is. Obviously, i'm not going to read all the text here, but we're going to hit some kind of key points here, one of the most important things we're going to go to kind of step, one and step two here step. One is if there's any frost if you're running a system in heat mode and it's a heat pump and there's any frost on the outer coil get the frost off before you take any measurements. This frost obviously is going to impede your airflow and it's going to mess up your measurements.

You can't compensate for that. Go ahead. How do we get the frost off? How would you get the front stopper? I would uh energize the reversing valve. Okay, run it and cool yeah and get the brush out that way, probably the easiest way: yeah yep um.

So first do that and then next check all the obvious things before you're going to do anything, especially before you're, going to start messing with charge levels on a system. Are you going to condemn any parts check everything, that's obvious first, this is where um and i beat this dead horse - a lot talking about wide narrow, wide diagnosis. So when you walk up to a system, it doesn't matter if it's a heat pump straight cool gas, furnace, heat mode, cool mode, doesn't matter when you walk up to a unit. First, take a really broad view, because what i see a lot of newer techs do is they'll, go up to a unit, they'll be like.

Oh, the evaporation is dirty. This is jones. You need to clean the evaporator club right and then they didn't notice that, like the capacitor was failed and the compressor blown it blew a terminal and like all this other stuff, so you approve the vapor full cleaning mechanic, oh by the way, like that sort of Thing happens a lot actually and it's not wrong, because you do want to pay attention to the fact that the coil needs clean. You do want to pay attention to the fact.

The blower wheel is dirty to filter all that, but you got to do all of it first. You can't just do one stop and quote the customer. So that's why we start why we start by looking at everything taking note of standard stuff, filter, evaporator, condenser, coil, blower, wheel, um, so on and so forth. Anything else that you can visually notice about the equipment go through all that and then find the problem.

So that's where narrow comes in start wide go narrow, find the problem find the thing: that's keeping the equipment from working quote the customer appropriately, always preparing them that you don't fully know until you do the testing once you get it fully operational. So just remind you know: i'm gon na this is this is the battery of things that we're suggesting bundle whatever um. This is the main problem. Once i get that all done, i'm gon na run test the equipment, check everything and make sure there's.

No other additional problems makes sense that kind of prevents a lot of heartache um, especially with the impulse that we have to rush to the customer and say i found the problem. It's simple! It's a capacitor right! I found the problem. It's simple! It's a drain! That sort of language gets us into more trouble than anything else we do in the in the field because we want to get it for whatever reason, especially as residential service technicians we want to get in and out. I don't know why, like we just we don't.

We, like, we don't want to be with that one customer very long. We want to get to the next job. It's a really bad impulse in heating season. It gets worse because we're not used to it as much.

We don't have as much reps on it. We don't have as much experience with it, so you can make more mistakes when charging in heat mode. Read your manufacture, specs first, because even within brands, there's going to be variation on heat pumps depending on the compressor technology, depending on coil size. There's going to be a lot of factors that impact how you charge these things, we got some rules of thumb, but they're, just rules of thumb, they're just there to kind of say all right.

I can tell that the system is basically working. Okay with no major uh huge glaring issues, but it's not the best way. The best way is to follow the manufacturer's specifications. Now linux is one that actually tells you to block off your condenser and do your tests in cool mode, even when it's cold outside.

So they tell you to do that. It's not my favorite way. I would probably prefer to use the uh the field piece charging jacket if you're going to do that, it's going to be a lot easier than trying to carry cars. It's like one of those things like who carries a bunch of cardboard on your truck and it's sort of a weird.

I know what eric does for that purpose, mostly for refrigeration, condensers blocking blocks yeah, but it's the same same concept. Yeah. You just find the right size, box and fold it up and stick it in your truck somewhere. Can't you just block off the condenser band to raise the head pressure to charge in cool mode the same way um it isn't it it cavitates, and so you actually it isn't as reliable.

It's hard to kind of get it dialed in because in order to do it accurately, it's not just a matter of blocking it off, it's a matter of getting it blocked off appropriately, so you actually get to your desired subtle level. So what i was told is take the temperature coming off the fan. You want roughly 95 degrees coming out of the system to simulate a 95 degree temperature outside to charge in an appropriate cooldown setting i mean that's that's i mean that's not going to simulate a 95 degree day, just because it's 95 degrees coming out. It's 95 degrees.

Coming out, you're stimulating significantly less than a 95 degree day, because that would mean on a 935 degree day the air blowing out. The top of your condenser is 95 degrees, and of course it's not so, and then that varies wildly. So that's what we call condenser delta t and condenser delta t if you've ever measured it, meaning the air temperature differential. It's highly variant and a big reason that it is, is because manufacturers use the same condenser coil size and the same fans over a wide variety of tonnages.

You'll notice this, like a lot of systems, the three ton of the four ton box is the same size. So that condenser coil is the same size. So your delta t swings a lot depending on the manufacturer, depending on coil size, there's just a lot of variables, and that makes it kind of challenging that isn't to say that it's not okay to do um. But it is it's another rule of thumb and a battery of rule of thumbs, basically the best way that i know how to do it and it's not that expensive is the linux.

The uh field piece charging jackets, probably the best way, if you're going to do that practice. Honestly, if i show up on a linux system, i'm not going to do it their way, but it's good to know their way. I'm going to go ahead and just run into heat mode and use my rules of thumb and make sure that it's in the ballpark and move on. If i'm gon na do a significant repair like a um compressor replacement or something like that, then i'm going to weigh in the charge.

I'm gon na look at line length and i'm gon na actually weigh in the charge appropriately and then i'm going to do my kind of rule of thumb tests. So i don't love linux's way, but it makes sense like i understand why they're doing it, it's just very highly variable and it's hard to hard to pin down what were you going to say? Do you look? If you don't have uh cardboard, you can use a trash bag too, and you can just start creeping it around the condenser until you get the appropriate amount yeah. Actually, that's that's a good idea yeah. So this is an old-school.

Um heating check chart uh the carrier used to have - i inverted the colors just to make it easier to read, and so here you're literally just looking at um. What is your, you know, dry bulb, wet, bulb, wet ball being the more accurate number here. What is the outdoor uh wet bulb temperature? What is the indoor drywall we go across? What are your pressures supposed to be and again, even that it's it's kind of it's kind of a rule of thumb. I mean it's, not it's not going to be super exact, but the manufacturer put it out so yeah.

It always frustrates me when people use rule of thumbs on a system that has a chart like this. It's got a chart like this use the chart right. It's a piece of cake now, one of the biggest questions is: when do you use heat mode charging and when do you use cooling charging techniques? Does anybody know where the cutoff line is temperature wise? When do you charge it when you check in heat mode, when you're checking coolant, does it stay on here? It usually says i think 60 65 65 is typical. It's not always 65 60 to 65 is typical, so when it gets below 65 degrees outside that's when you're going to follow the heat mode test or low ambient check guidelines.

Obviously, if you're at 65 degrees, you're going to probably just check it in both modes and really checking in both modes when you're in the edge season is your best bet anyway, you know if it's anywhere from 60 to 70 degrees outside checking in heating and cooling, A little bit of runtime is going to be your best bet, next rule of thumb, the good old 100 degree over ambient discharge rule. So those of you who have been doing this a while do you like that rule of thumb, bert, sam um? I hated it at first, okay um, i found it was more accuracy when i actually let the system run a lot longer than i realized. Yes, very good, so very good one. I never.

I never saw any consistency, and i didn't realize you know 25, maybe longer 25 minutes, maybe longer yeah and that's true of any charging any anything like that. You can't run a system five minutes and set a charge. You can run in five minutes and know whether it's flat or whether it's significantly low but you're not going to be able to set a charge in it drives me crazy. When i see people it's like.

Oh, my subcool, six, let's start adding some refrigerant and the things run five minutes. You know it's like. No, obviously, if your suction pressure, uh on a you know, 95 degree day outside is giving you 90 or 25 degrees suction saturation. Well then, yeah.

At that point you know it's it's low, but but not if it's just showing a little low, so cool you got to let it run long enough before you start messing with it. The reason i don't use it as much is because a lot of times you're showing up uh in the winter, for us doing a maintenance - and you know you don't usually run a run to customers - heat 30 minutes. You know around here you could probably pop in there so yeah and that doesn't make it tough for that purpose, but it does work if you're doing a diagnostic you're trying to figure it out. It's a pretty decent range.

If you let it run long enough, yeah. So the rule is more like 100 to 110 degrees has been my experience, um and the way this works is you run a system in heat mode, like burt, says for a reasonable amount of time, 15. 20. 30 minutes and then you measure your discharge line temperature at the outdoor unit and it's generally going to be around 100 to 110 degrees hotter than the outdoor temperature.

So if it's 55 degrees outside it's going to be 155 to 165 now, if it's significantly higher or lower than that, that's when it kind of gets weird, because it's sort of a bell curve like you, can start to see weird measurements on both sides like if It's really low or if it's really overcharged, but it's really more of an aid to just say: okay, if you're in that range, that's a pretty good indication that you've got at least close to sufficient charge. Any dispute of that okay, not really a pump guy. That's right: eric's, not not a heat pump guy, all right, so this is an example of me of me making this test with my old fluke. My flute clamp, um and you're.

Literally just you really! You don't even have to do this, measuring you don't even need gauges, it's just a measurement of your discharge line, the artist formerly known as your suction line, your vapor line and comparing it to outdoor temperature. So if it's, you know, 58 degrees outside that would be appropriate temperature and, as it turns out, that is about what it was that day or 60 degrees in that range. So that is an indication of a system, that's at least close to proper operation um. I don't know i zoned out for the last 30 minutes, but if you've said this already, just let me know, but you have to inspect the system first like if you have clogged uh, condenser, coils, yeah, now you're evaporating right, like you, can compare it to the Outdoor temperature right because you don't even have a clean coil did i did.

I mentioned that first, that you got it yeah i did yeah yeah. Can we go or she's sitting right, weren't you sitting right here when that happened. Yeah i gave input about it. Did you oh okay, but then you just forgot that it existed.

It just needs to be mentioned again. You can't just go off of the outdoor temperature, correct. You have some other oils or a filter inside. That's really dirty other other things that are affecting the system.

In an extreme way, absolutely beautiful, beautiful, beautiful, all right, um, the suction pressure, evap uh, dtd, rule of thumb um. So back when we worked on r22 systems, there was just this weird coincidence that your suction pressure on a properly charged system would be about the same as your outdoor temperature. So i want to say this again: it's completely it's just a fluke um that if it was like 50 degrees outside your suction pressure on an r20 suture system would be about 50.. Yes, burt.

I noticed that that didn't apply if you had a really clogged coil outside um you're barney fighting this thing up right now: yeah uh right, that's the reason why you're doing it is to indicate whether or not you could have other problems um but but to convert That to modern refrigerants, instead of using this weird pressure to temperature strange relationship. Instead, you do 20 to 25 degrees, suction saturation below outdoor ambient. So you take your outdoor temperature, so say your outdoor temperature is, you know, 40 degrees. So it's a really cold day.

Then you're going to be somewhere between 15 and 20 degrees, suction saturation, meaning your evaporator temperature there's a lot of different names for these things, but the correlating temperature that goes along with your suction pressure is going to be 15 to 20 degrees. Fahrenheit. Does that make sense what i'm saying there so joel you walk up to a house and you're gon na check in heat mode and it's cold outside and you're like because this is. This is practical.

Let's get nitty gritty here for newer techs! You walk up to a house you're like it's cold outside. I want to check this system. You hook up your suction gauge and you're like holy moly. This thing is flat: it's really low right.

You got to remember that when the outdoor temperature drops, your suction pressure is going to drop and it's going to drop proportionally with um with your outdoor temperature. So your evaporator temperature is going to drop along with your outdoor temperature and the same way that uh your suction pressure drops when indoor temperature drops on cooling mode. So if you've ever noticed, if you start a unit up and it's really hot inside the house, the suction pressure is really high and then, when it starts to cool down it comes down and that's typically a 35 degree. Dtd design, temperature difference 35 degrees less than the indoor temperature is what you find in cooling in heating, it's more 20 to 25 degrees.

That's because one reason is because it's a much larger coil proportionally. So it's a very large evaporative coil. So that's actually a pretty good indication, and the nice thing about that rule is that rule is going to hold true, no matter what happens with new refrigerants. It's not going to change too much because there's some limits to physics that cause that to be there, um that rule's gon na kind of remain.

So if you go to a house, so let's make it practical, go to a house and it's 30 degrees outside and you hook up to it and you see that your suction saturation is 5 degrees. You're going to think. Oh, my gosh, this thing's going to freeze up this is terrible. This is low.

Yes, it will freeze up and that's why you have defrost, because it's a heat pump and so that's appropriate. But if you hook up to it, it's 30 degrees outside and you hook up and your suction saturation is negative. 10. Then that's the problem right or your suction saturation, it's 30 degrees outside and your suction saturation is 20.

Then that's going to likely be a problem. So just gives you a nice rule of thumb, and this is actually of the rules of thumb. This is probably my favorite one in heat mode, because it doesn't require as much run time. It's not relying on like the thermal conductivity and the distance between the compressor and where you're measuring, because even with your discharge temperature over ambient, it really depends on where you put that clamp, because that temperature change is pretty quick depending on where you put the clamp.

You put that clamp right near the compressor. It's going to be significantly higher temperature, which actually comes up when you're working on a heat pump package unit. You hook up right next to the compressor and it's like whoa. You know my my.

I don't know that you'll say whoa like that, but you might you know you never know whoa nelly. This thing is hot hotter than hades um all right. So that's that's a good! That's a good rule of thumb. Next one is a head pressure or ctoa.

Ctoa stands for what does anybody know what ctoa stands for condensing temperature over ambient right now? Where is your condenser in heat mode inside right? So, whereas condensing temperature over ambient and cooling mode is about the relationship between your condensing temperature and your outdoor temperature in heating mode, it's about the relationship between your condensing temperature, your high side, gauge pressure correlated to a temperature and your indoor temperature. Okay, now opposite of where, in heating mode, your dtd is lower. On the evap side, now it's going to be higher so 30 to 40 degrees. Condensing temperature over ambient is going to be typical, but it's highly variable and the reason it's highly variable is because that's very much tied to airflow indoor indoors and coil size.

So if you have an oversized evaporator coil inside you're, going to run a lower dtd, condensing temperature over ambient or ctoa. So all that means is that you're going to run higher head pressure when you have a smaller coil with lower airflow and you're gon na run lower head pressure when you have a larger uh coil with higher airflow and because systems aren't all the same. That's gon na it's gon na vary quite a bit in heat mode. You want to test it at the speed that it would normally operate at a high stage like you don't want to trick it like you, don't want to go in and tell it to run high speed when that's not what you're going to leave it at.

Obviously um, but i'm actually a pretty big fan of running uh, your your heat pump, air flows at high, you know higher speeds and that's uh. You know carrier's traditional heat pump, efficiency mode because they have heat, pump, comfort and heat pump efficiency. That's what that is at least they changed it. I'm speaking and now i may be saying the wrong thing, but at least it used to be this way or when you put it on heat pump efficiency, it would run higher airflow in heat mode.

So, let's ask the question: while we're on the topic, why would people think it's more comfortable to run lower airflow in heat mode on a heat pump? Why would they think that anyone? Why would it be more comfortable to people to run lower airflow and heat mode on a heat pump? The air comes out warmer air comes out warmer when there's less air flow. The air comes out warmer, but what happens to the system when there's less airflow in heat mode inside compression ratio goes higher head pressure increases. I said that opposite direction of what i wanted to head pressure increases. Therefore your compression ratio is higher.

So what does that mean? That means the system is not running as efficiently it's not putting out as much capacity and it's harder on the system. The compressor is running hotter compressors that are running with higher compression ratios run hotter. So i don't love it. Systems would run better with higher heat pump airflow, but the downside is customer that air don't feel hot.

You know that's what that is, and that's exactly how they all talk to that airflow ain't hot, just like that so um. If it were up to me in heat mode, i would run high or higher airflow, so you could bring your head pressure down if you're running a system that has high head pressure, we'll just go ahead and jump to this since we're talking about it, you hook Up to a system, your discharge pressure or your liquid pressure is really high. Don't jump to the things overcharged. That's everybody i'll start dumping some charge out of this thing same thing with heat pump, pool heaters.

First thing: people do they see the higher somebody overcharged. This thing i mean they may have, but in many cases it's that you don't have proper air flow over your evaporator coil on a pool heater is that you don't have proper water flow, so you're not moving enough water, so dirty air filters, dirty blower wheels dirty Evaporator coils um blocked, returns, kink ducts, you know returns that are collapsed. Whatever all those sorts of things are, what cause uh high head pressure on heat pump systems and heat mode. Those are the most common things and actually another very interesting thing that you see a lot of times is you'll go up to a system because in florida you know, you'll have a cold night and then you'll have a hot day and a cold night hot day.

So people will be shifting in between heat and cool all the time. You'll go to one of these older. You know ream used to have these resettable high pressure switches, there's red buttons, you'll go out and the red button will be tripped. But now it's you know a warm day, so they're running you reset it running cool mode is running just fine, no problem.

What's the problem? Nobody, i don't know, what's going on, i just i guess we just have to keep bashing that red button, but the they were notorious uh for bad airflow. With certain models i mean it wasn't necessarily their fault. It was the way people were installing them, they weren't following the manual but um, but they were notorious for their flow problems. And so, when you have poor airflow inside on a heat pump that head pressure can go up quick and on some models it can go up really quick, depending on the size of the coil and some other things also notorious for leaking on that switch clicking on The push button i never saw that leaking refrigerant.

You've, never seen that nope. I haven't either this guy's crazy. I know he's a lunatic. I thought he doesn't work on heat bumps.

What's he talking about? Oh okay, they do. They did okay, you're talking about the red button, yep yep and sometimes they put a quick uh and sometimes they put a quigulator on it. Isn't that what it's called a quick later charge? Compensator yeah? But what do they think about a different style? Coigulator yeah yeah? We can talk about charge, compensators that'd, be that's a fun conversation but anyway um. So we're talking about just some basic some basic rules of thumb, um so 30 to 40 degrees, condensing temperature above the indoor dry bulb.

So here's what that looks like joel. So you walk up to a unit and it's in winter and it's 65 degrees inside the house. That means that you would expect your condensing temperature, meaning you know you look at your side gauge. You look at what temperature that correlates to to be somewhere between um.

I forgot what number i said: 65, 95 and 105.. That's what you would expect it to be based on that indoor temperature, if it's 125, 135 545 look at airflow, first start there. If it's, because that's too high right that pressure's too high yeah! Another thing: that's kind of interesting, with heat pumps and and we'll just talk about this quickly - is that their capacity is highly variable, meaning that in air conditioners we don't see a. We don't see a huge swing in how much capacity they produce, especially in a market like ours.

So uh, you know the system. You know three ton unit isn't going to produce significantly different capacity. I mean a little bit, but it's not going to be a huge swing from it being 75 degrees outside to it being 95 degrees outside. If you're in phoenix arizona and it's 130 or something crazy like that or death valley, then yes, the capacity drops off a lot but a heat pump.

We expect it to run under a much wider range of conditions, so we expect it to heat somebody's house when it's 55 degrees outside, and we expect it to heat somebody's house when it's zero outside and then we're talking florida here, because it does get that cold. Sometimes especially if you go nor north of villages ocala that sort of thing, so that's a wide range and the amount of heat that a heat pump produces when it's 55 degrees outside and the amount of heat that it produces when it's zero outside is significantly different. Not just because there's you know it's more challenging to get btus out of that outdoor air. Just waiting for bird we're just going to wait.

Just we're just going to wait. You know. Sometimes you just have to wait um it's because when that outdoor temperature drops what happens to your suction pressure, we already talked about this. So i want some of the younger as what happens in suction pressure, when outdoor temperature drops in heat mode on a heat pump.

Drops right so when your suction pressure drops, but your indoor temperature stays the same right, what happens to your condensing temperature if the indoor temperature is staying the same or trying to hold the same, does your condensing temperature drop? It's not a trick question a little bit. It might, but it's not going to be a lot, and so what happens when your head pressure stays almost the same, and your suction pressure drops? What do they call this differential between suction pressure and head pressure? Anybody know what that's called depression: a compression ratio, compression ratio, the higher the compression ratio, the less refrigerant that compressor can move and the easiest way to think of it and we've talked about this in the past - is simply because, when you drop suction pressure, what's happening To your gas, it's getting lighter, so meaning it's less dense and when you have less dense gas and you've got this compressor pumping away it has less to grab onto you know it's like running a fan at altitude, where the air is thinner and lighter you're, not Going to move as much air because there's less air to move and the same thing is true, with the compressor when suction gas gets less dense, the colder it gets outside the less refrigerant it moves. So when you think about the magic of just kind of segue to like modern inverter driven compressors, because you know you'll see like these things, keep their full capacity all the way down to zero degrees or my negative 20 degrees or whatever you ever wondered how they Do that yeah? How do they do it? I've wondered it, but you don't know uh. No, i don't.

Okay. How they do it is. Is that as that suction gas density decreases, they just start spinning the compressors faster. That's all so they're not as efficient, but at least they can maintain their capacity.

So in order to as that as it gets colder and colder outside, as that gas gets lighter and lighter, and naturally that compressor is going to move less and less you spin. The compressor faster you can keep the capacity up, make sense and that's why, if you, when the green speed first came out, you had to put those giant mufflers on them, because when that compressor starts spinning up at these really high rpms, you get this strange resonance. That makes all kinds of crazy noises because you're spinning the compressor faster than you've ever spun those compressors before now. Obviously they have to be designed for it.

You know so it's not like they're not designed for it, but you get weird noises when things move at higher frequencies than normally they would make sense. So you learned something new, didn't you? Would you look at that? Would you look at it? Would you just look at it if you find on copeland's app a compressor, that's rated for air conditioning and refrigeration, you can see exactly how much capacity you're losing by dropping evaporator temperature, and i remember looking at one that was 20 tons of cooling over air conditioning As a freezer, it was four tons: oh yeah, yeah, that's dropping your evaporators 65 degrees for four times, with the same compressor and electric input and you'll see that with um low temp to medium temp too, i mean you have a you, have a compressor that they Can do both when they get down to that lower edge of their operating envelope, but copeland talks about that all the time they're operating envelope, meaning the conditions under which the compressor can operate. When you get down to the lower end of that, where you have higher compression ratio and that's primarily due to lower suction pressure, colder evaporator coil equals lower suction pressure. Simple concept right.

So if you're trying to keep ice cream cold - and you want to keep that ice cream, negative 10 degrees - then you're going to have a an evaporator coil, that's lower than negative 10 degrees right. So that means that if you've got an evaporator, that's you know negative 20 degrees, negative 25 degrees, whatever that's very low suction pressure, when you have very low suction pressure, you're still rejecting your heat to the outside right. Even so, you have a grocery store, you're still rejecting heat outside, which means head pressure is still staying up here, but suction pressure's way down here, big compression ratio, very little capacity, sort of a universal concept and that's how we actually get more efficiency out of systems, Meaning we spend less and we get more capacity, is by dropping compression ratios and the easiest way they always found to do. That was big evaporator coils lots of airflow big condenser coils lots of airflow, so you're just rejecting both sides, you're keeping your evaporator temperature up.

You're, keeping your condensing temperature down better capacity all was great until we realized they didn't dehumidify worth of crap when they're set up that way. So it's like a problem, but that's a florida thing all right so checking without gauges. So i like to do heat pump tests without gauges where possible. Now i just told you that my favorite test is just looking at suction saturation compared to outdoor temperature, and that does require gauges.

But these are some things you can do to check it without gauges. Again, it's got to be frost free, the outdoor temps need to be between 65 and 15 degrees, fahrenheit again most of the stuff. I just literally pulled out of my rear end. I just made up, you know kind of basing it on my experience and what manufacturers say um, so don't take it too seriously and once you've already inspected the whole system.

You've, looked at evaporative, coils, you've looked at filters, you've done all that, like burt was about to mention again, so we first check the discharge vapor line. It should be 110 degrees above the outdoor ambient temperature. Your suction line temperature should be 5 to 15 degrees cooler than the outdoor temperature. Now this is taking into account superheat and my rule of thumb.

Liquid line should be 3 to 15 degrees warmer than the indoor temperature and delta t indoors, because this is the one that a lot of people like what should my delta t be? What should the difference be between my return and supply air temperature inside it's going to vary wildly like wildly, because not only are there design differences in equipment, but there's also these huge swings and ambient conditions that you could be operating in so you're going to see A much higher delta t in cases where you've got an evaporative coil that is small, with low airflow and when it's warmer outside and then the opposite is true in the other way. So it's just it's just not that valuable. If you really want to do a very thorough job, you can do deliverance capacity delivered capacity is easily done, so you take a digital, psychrometer and return supply hook up to measure quick. You know you'll get a pretty good indication of what capacity that system's producing, but that capacity is going to vary a lot too, depending on what the outdoor temperature is.

So you got to kind of like take it with a grain of salt or reference. A manufacturer chart in order to know for sure imagine using a chart and measure quick together, like a manufacturer, chart and measure click together. Like imagine how good you could be as a technician yeah, why are you saying that this feels like a setup? Just imagine i can only imagine yeah yeah yeah mercy me that bad boy and i'm saying all right. So any questions about any of that.

Do you need a hygrometer when you're doing that? No, you, don't you don't it's just that's what that's what's going to connect to the app that's going to make it the easiest to do, but, but no you wouldn't. You could use regular thermometers for that matter because you're, not you, don't, have a latent change across a condenser coil because you're not going to you, know you're, not dropping water in heat mode right. The reason why you need cyber psychrometers or hygrometers, whatever you want to call them um in cooling mode, is because a lot of that heat is latent, and that makes it tricky. So you have to measure change in relative humidity or change in total, moisture content as well.

You have to compensate for the latent capacity, so those are the ways that you check now, if you are we'll just back up again, because if you're doing a new install on a new piece of equipment and it's 40 degrees outside, i would much rather you follow The manufacturer specs weigh the charge in and in our market just you know, go back for half an hour another day and just double check. You know like that would be my preference probably still not going to happen, but that would be what i would suggest to most people. If it's, you know, if you're in a market like ours, where you just don't, have that long of uh of a cold snap season or a winter, it's you know, i don't know why. I called it cold snap season.

That was a really weird name for the winter. That's what we call it back in the woods. We don't call it winter. We call it cold snap season and jimmy crack corn, but i don't care um anyway.

So that's not that's not how that goes. I have no idea, i don't know, i'm really confused, i'm totally confused now, anyway, um. If you have a fairly short winter in your market, then you can always just go back once it's warm outside and actually check it using subcool method or whatever. If you're in a market where your winter is longer than your summer, then whatever practices make sense in your market is what i would suggest, but anyway, all right.

So right now we're in cooling mode. If this were a lennox system - and we were wanting to drive up our head pressure in order to test it in cooling mode with it being cool outside, we would use the charging jacket. So i want us to it's, not something we use a lot, but i want us to go ahead and just experiment with using that real quick. So i'm going to give it to joel to assemble.

So if you read the destructions on it, it says only use on txv systems, so this is for systems that you're going to be setting the sub cooling in this one's never been out of the bag before so all we're going to do is hook these bad Boys around the around the outside, like trailer park, girls, it's eminem reference, okay, huh, that's how the song goes trailer park. Girls go around the outside around the outside right outside yeah, probably not, but i don't actually know that they're not so it's not uh. There's no impure thoughts for me, restricts airflow and you can like adjust it. Are you, okay, all right, all right, so huh, it's the worst jacket? It's not! It doesn't keep you very warm all right.

So, let's look at this is this is eric's. This is scary. Never never grab another man's phone and just start flipping through it. That's something that i've learned a long time ago, um andrew grieves about took leilani's head off, for he was like i'd, say, showing her something on his phone and like, rather than just looking at it.

She like grabbed it and he's like what are you doing all right, so take a look at this right now, we're at 99 degree saturation on the liquid side and 43 degree saturation on the suction side, which is fairly, you know to be expected, but as we, If this was a cold day and we wanted to drive up our head pressure - and we can kind of keep this here - you want it more loose, so it can actually air connection escape down the sides, so you're actually dumping hot air down the side yep and It says here what you do so you then this one you only use from the dry bulb temperature between 37 and 70 degrees and you're supposed to keep it below 500 psi for an r410a system. It says here adjust the restriction of the charging jacket until the difference between the high side and the low side. Pressures is between 160 and 220 for r410a. So it gives you specific instructions on how you would use it and then you're going to check your target sub goal.

Yeah you see now we're now we're at 103 up there we're at 117 119 we're really really getting there. So it's just more of a controlled way now again running in cool mode. So this isn't a heat really a heat mode test. This is just a way to check the charge in sub cool with the txv under certain load conditions, and it's actually fairly easy to do so that you don't have to try to set a charge in heat mode, we're already at 450 psi.

So we can go ahead and if you adjust it out, then you can get that head pressure back down again all right. So now we get the point: let's go and shut it off, and let's look at our defrost and uh inside our condenser a little bit. We'll talk a little bit about about that. No, i just take it off.

Okay, that was all that was all just showing just demonstrating it. You know it's actually, it's a pretty good design. Actually, it's easier than a lot of your options, all right. So first question is: why does a heat pump need defrost, but why will that frost up yeah? Why would it freeze, but why design suction saturation job okay? So what is what do i call the evaporator coil? What's my kind of simplistic name for the evaporative coil, the heat absorber right and what direction does heat move? What temp, what direction does heat move left to right? It goes from higher temperature to lower temperature right.

So if i want to get heat out of the outside air - and i want to get it into the evaporator coil and the outside air is 30 degrees. What do i have to do the evaporator coil in order to get heat to move into it, get it below 30.? I got to get it below 30 degrees right. I have to get below 30 degrees and it's and if the evaporator coil is below 30 degrees, because this is the evaporator coil in heat mode right, what's going to happen to the surface of the evaporator coil, eventually it's going to freeze and what are the factors That dictate how fast and how quickly or how quickly and how much ice is going to build up on that evaporator coil outdoor temperature. What else outdoor humidity, outdoor humidity air flow run time right? You got a system, that's running a lot! It's going to be much more prone to freeze up than a system.

That's not running a lot. It stands to reason, um. What? If it's? What if it's raining, you know what, if there's like a light rain or something like that and that that could add to it, because now you actually have liquid water, that's impacting the coil. It's raining hard enough.

It actually might yeah prevent it from frosting, but depends on the depends on the temperature so um in florida. We don't see a lot of you know: sub 40 degree temperatures, it's not common, but it does happen and when is it the coldest it's in terms of yeah night time?.