Any service tech that doesn't have one of these on the van we have some back there, they're really great. I'm going to talk about really basic um heat pump heat checking operation because this week and last week got a lot of calls about stuff that we've taught a lot of classes on and done a lot of training on. But when you don't see it, maybe for an entire year or you, you got a class a few months ago, but you didn't see the problem until this week. Then it can be hard to like.

So if we talk about it again, while it's fresh in our minds connecting it to systems we'll be looking at today, then maybe we can retain it a little bit better and that sort of thing yeah. A lot of the calls that i got were questions about the refrigerant system in in heat mode and what to expect as far as pressures go and those kind of problems, i'll just jump right into that, and then we'll just talk about um. To finish, just practical stuff checking um systems this time of year when it gets as cold as it is, and you guys can be as interactive as possible with problems that you've had recently and questions that you have as i go. First of all, in heat mode, i've written down a few rules of thumbs that apply to most systems and they're, not exact.

They are rules of thumb you i, unless you have like the manufacture, chart opened for that system and the system's coils are clean. They have original fan motors in from the manufacturer, they're an actual match inside and outside, like the systems are designed for each other, then you're gon na have um you're, not gon na. You know, unless you have all those things exact, you're, not going to see really really specific numbers that are easy to chart in heat mode. Here's some rules of thumbs to kind of help you a lot of times when you show up at a service call this time of year and the heat's not working.

You can burn a lot of extra time on the areas that you don't know that you don't understand, and so here's something to help you, maybe just a little bit quicker, get through the refrigerant, so discharge 100 degrees above outdoor temperature is a pretty common rule of Thumb for heat mode, so where's our discharge. Where would we check this temperature used to be the suction line cool mode, so the fat line right outside the condenser, the fat one? That's now our discharge line right. That refrigerant is coming straight from the compressor. It's really hot: it's really high temperature and it's in vapor, and where does it go next, okay to the air handler and which is now the condenser okay, so you have really hot discharge gas going into our air handler evaporator coil, and so how does that heat? The home, why does that heat the home when that happens, what okay and then the coils radiate heat into the house? Yeah blower motor pulls it across the coil yeah.

So now our fan in here is like our condenser fan outside it's pulling air across the coil. That's colder than the coil and it's the heat in the coil is moving to the colder area, which is now the air and then that air is being pushed back into the house. So the coil is getting rid of its heat. And when you have hot discharge gas that gets rid of its heat, what happens to the state of that gas so that gas begins to condense into liquid? And then liquid comes out on our liquid line again liquid line, you can see the range here.

It's pretty extreme right, but that liquid line coming out of our evaporator coil now in heat mode. It's still the liquid line. Liquid line always stays the liquid line, but it's moving in the other direction. Now you can expect it to be 3 to 15 degrees warmer than indoor temperature.

Why would it be a reference to the indoor temperature on the liquid line yeah, because the temperature of that liquid line is directly connected to the temperature of the air? That's coming across that coil that is converting the refrigerant into the liquid right. A lot of the questions i had this week were also just basic stuff like this, which which direction? Is it going and what's happening in this area of the system in heat mode? And this can happen because, even if you, if you were to stop and slow down or if we were sitting in a class talking about it, you could figure it out pretty easy. But then you show up on a call and you're, not sure. What's going on, you get overwhelmed and suddenly everything on that system feels possible.

Anything could be happening here. It's magic who knows: what's going on use this to help you figure out if you're in that, in a range that looks normal, uh suction line 5 to 15 degrees colder than the outdoor temperature? Where would you hook up to get a temperature of your suction line? Yep yep so common on the inside of the condenser. That's the only place it. Your suction line is between your evaporator coil and your compressor.

So what's your evaporator coil in heat mode, yeah? What's normally, the condenser coils outside is now the evaporator coil, so your suction has to be between that coil and your compressor, which is all inside your condenser. You can put a clamp on the suction line before the compressor right after the accumulator right before the accumulator. Just inside the condenser, if you're a train, if you're working on a train system, where could you put that clamp yeah, so there's a panel on the side? I got a call from someone that said that they were pretty sure the unit was running in heat mode, because the discharge temperature, the suction line - was really hot. But there was no reversing valve and there was no common port hookup and i was like.

Are you working on a train? Yes, okay, that shows how little we are seeing problems in heat mode, but it also shows that somebody's probably been doing a lot of maintenances and not checking pressures in heat mode right, yeah, the side panel on the train. You can open it up and you have your reversing valve right. There yep, you hook up your gauges right there. You got your discharge, your suction and also your txv trane is going to use a txv to meter the flow of refrigerant into the suction working on a train system and heat mode is kind of nice, so the split indoor is going to vary a lot depending Upon outdoor temperature, how warm it is inside, if you have the heat strips running or not, and what size heat strips you have and the speed that your blowers set on.

So it's not as easy to have any kind of a normal split. I'm not going to use any type of rule of thumb for your indoor, hot air temperature split okay. So all this was taken. I wrote it down this morning from brian's article on checking heat mode, which he did that you know two hour class on in the middle of summer, so you can go look up the video.

If this is all new, go look up that video watch. It checking charging heat mode and you can look at the article, which is actually pretty short, some good tips on checking heat mode. That would be important. You feel at all, unfamiliar with your heat pump cycle.

I was looking at this over again. They have in it, which are several books back there for service decks, that you should have on your van and going through different problems that you have, but we have our heat mode with labels on the equipment in here and um. I think we have like 21 labels and then a description on what's happening in each place. The direction of the refrigerant and the chart so take a look at that and get familiar with heat mode.

You can even take some pictures for reference point: i'm not going to go over the whole refrigeration cycle this morning in heat mode, and so some of those issues that we've running into is you know. Maybe a customer replaced the thermostat or somebody replaced the thermostat and they didn't set up the auxiliary backup heat it wasn't wired in or maybe it's one of those cheap thermostats. That says it's compatible for heat pump, but it only can bring on one stage: heating heat pump or electric, not both simultaneously or it could be. A fancy thermostat that you have to go into the menu and select auxiliary heat runs with compressor some of the older ecobees or core thermostats.

You have to go in there and actually select that, if you're getting a call, an issue with heat then actually find out. Why the heat strips aren't running if the issue is related to refrigerant and you need to actually add refrigerant when pressures get this cold, i mean when temperatures get this cold pressures get so low. It can be hard to actually gauge whether you're, adding the proper amount and even like manufacturers will tell often will tell you. You know when you're, adding in heat you're, going to try to get your pressures and temperatures to match up either.

Rules of thumb or the chart from the manufacturer that you have understanding that you still don't know if you're perfectly or accurately, adding charge and heat you just can't what are some ways that maybe you could set charge better this time of year, if you're running into A charge issue, first of all, what's the perfect way yeah, the perfect way is to quote the customer to recover and weigh in the refrigerant, so you could recover what is there and you could add back from the tank until you run out of liquid and then The rest that would be needed can be quoted right there, the customer hey. My me, your system hold eight pounds, i pulled out three pounds, and so i'm gon na charge you for five pounds to get this working again and you guys already know the process and procedure for leaks and then, if you're doing an install and typically you could Turn on your system in cool mode after you've done your install and find out. You know my sub cool actually looks right. Am i a little bit low on refrigerant? Do i need to add it in where that's not going to be accurate right now? How are you going to know how much refrigerant to add right now on an install charge by chart? So what do you mean by that? The manufacturing chart inside the condenser panel should have a chart based on the outdoor engine temperature, and the pressure should look like and they'll tell you that if it's lower than 65 degrees, then you can't be using cool mode to charge accurately.

So then that won't work. Today, we'll have heat load charts as well, depending on the manufacturer - i guess yeah, so the best way is to actually you understand your system charge that your system comes with and then your line length and you add the proper amount of refrigerant per the length of Line that you have, and so if you go to your hvac school app, you pull it up. One of the tools that they have there is a calculator you type in your line size. You type in your line, length between condenser and air handler it'll.

Tell you how much additional charge you need. You should be using that through the summer anyway, when you do a system - and you just type that in and you know, right off the bat. I should be adding this much refrigerant after an install before i turn it on and find out whether my system's actually running right or not. Okay, another thing: a lot of issues that we've had surprisingly in heat mode is that systems are not set up for and even though they should be set up for two stage and so then we're having issues in heat mode as well uh.

Your compressor is not running to its full capacity or your blower is not running to the full capacity. I had a situation where the blower was set up to run in low stage and never run in high stage, probably to help with humidity in the summer, but come winter time. The compressor's running in high stage with the blowers not - and it's going out on high pressure. Why would that cause it to go out on high pressure yep, so the evaporator is condenser at this point, the evaporator high pressure is happening in there that heat that the compressor is generating.

It needs to go into the air, otherwise the pressure's just going to keep building and the temperature is just going to keep building until you go out on high pressure so inside that coil the cold air from the house comes across it, and so you need the Actual amount of airflow to match how much hot refrigerant is being dumped into that coil. So if you have two stage hot refrigerant being dumped in that coil, but your blower is still on first stage then, and maybe the house is 69 degrees and they want it at 72 inside that house, that's a perfect storm for going out on high head pressure. You know you've been already not that cold inside the house, you're not running in high speed with the blower, so you just don't have a lot of cold air coming across that coil. To get rid of that heat air flow has a huge effect on heat pump when it's in in heat mode inside.

Knowing that you need to be checking your filter and if your coils clean as well right. So back to heat strips when you have a heat, strip's, not working make sure you have a call. When should you expect to call like how? How might you trigger the thermostat to send the call immediately yeah? I prefer raising it up high and once you raise it up over four degrees, most thermostats are going to automatically bring on that auxiliary heat. I prefer that method, because then you get to see it in real time like the way the customer is going to experience.

It put your temperature really high and you usually on the display. It'll show that the backup, auxiliary heat is calling on the thermostat, and then you can go into your air handler and take your amp draws to find out if it's actually calling. Where should you take? Your amp draws your 240 coming into the air handler if you are just checking your heat strips, so this is a 10kw right, five and five. So if you take an amp draw - and you put it on here - how many amps am i going to pull 20.

so 5kw pulls between 18 and 20 amps. So i'm going to pull 20 here and then i'll pull 20 here and then i might just walk away from this and say i have a 5kw heat k in there, not understanding that actually both of these are pulling 20.. So, together my total is 40., but if you take it at the power coming in from the breaker first, as it goes into the air handler, then you're actually going to have your accurate amount. This is important because you're going to run into systems, not cooling.

Well enough, because half of their heat kit is running especially on package unit, maybe they haven't actually set up for both stages to be calling, or maybe you have an issue with one of your relays. You have two relays in here. Maybe one of the relays is down and you can't just clamp on and say: oh well, i have 20 amps, so i think it's working you need to actually look. Do i have a 10k in here? Do i have a house that has a 4 ton or a 5 ton? I need more than just 5k as backup heating.

This house mat needs more than 5k uh in weather like this and so actually knowing where to check and how to check. That is important. Also replace the heat strip that i just wanted to show as an example, the technician listed, the heat strip as failed we've, been doing a lot of heat kit replacements. When you have a heat kit, that's failed.

It's usually a very provable, easy problem to find provable. You can actually list in your notes what issue you found with it right, so this heat kit right here. Can you guys see where our problem is right there, so yeah, it's open. So this heat kit has a safety on here.

This one right here, which is a a pad, a bi-metal that will actually move and break connection between here and here so power can't flow through if it gets too hot and then it will uh once it cools back down. Those metals will come together and it can run this. One right here is different, it's a one time, so it has to get very hot in order for this to melt, usually this has to stop working, shutting it on and off. In order for this to get hot enough to actually melt and break like a secondary safety yep, it's like a secondary safety.

Most do have a secondary safety built in. So you have the resettable one and the one a fuse link, which is what this is called. A fuselink where it gets hot enough, it actually melts you got to replace it. You can look up the specific part and have buddy quote the specific part.

That's fine heat kits. Aren't that expensive, quoting the whole key heat kit, is, seems to be what we have been doing a lot. But i want you to actually know why you would be quoting the whole heat kit and listed in your notes or something something like this. When we go back to replace this, what should be the thought on our on the technician's mind when they come back and they replace the heat kit and they pull it out, and they see this right here, yeah? Why? Why in the world would that heat kit get so hot? What could cause that to happen? Anybody, what's that, okay, so low airflow would have to be very low yeah.

So you could have this not working, that's true, but at the same time, if this needed to be coming on and off, we had another problem. It was already getting too hot um. What's that going to be over amd nope, so in order for it to over amp, because it's a fixed resistance, you'd have to just have a crazy high amount of consistent voltage traveling through there, so not really a likely problem. So it is all related to airflow.

Like matt said, and so you could have really dirty filter, you could have a system that, when it goes into heat mode um, the blower is not set up properly. For that, you notice that on our x13s we have a tap on blue. Usually it's the color or or number two and uh, then a tap on four. That's usually connected to white, because when you're bringing on heat and you have a heat pump, you're going to need more air flow, you're already bringing getting absorbing the heat from the coil.

But now you got to get rid of heat on this as well, so they increase the airflow for heat, so seeing making sure that that's actually set up properly, but also when it's this extreme, you likely had a blower that didn't come on or a blower failure. It may be a module working intermittently, something like that. So just being aware and looking for those problems, don't just replace the part and and run. The last thing i wanted to say is that most of the issues are very simple and practical, not understanding completely and feeling overwhelmed by.

That is okay, when you're showing up to do the calls, but start with what you know. I know how to turn it on from the thermostat. I know how to watch it. I know how to check if the filter is dirty.

If we have blower restrictions, i can check something like these rules of thumb. Pretty pretty simply. I can do this, so you start out by doing all the stuff that you know and most of the time you're going to solve it. I think i mentioned before, but i just want to reiterate again: if you have a house, not cooling, find out why the backup heat is not running.

In addition to fixing the heat pump with your normal heat pump problems, cool anybody have questions or issues that they've run into recently that they want to use in this example, or you need to charge your system, what port do you hook up to charge? So the common suction port is your suction, so you're going to have to charge through that you'll turn on the system, your middle common suction port hook up to there you're adding refrigerant same if you're doing an install and you've calculated the line length. You use your calculator from hvac school you're, going to add refrigerant through the common suction port when the system's running, because that's where your low pressure is and that's how you'll move it from a high pressure tank to a low pressure system, it'll suck it in through The common section trains they don't have like eating sharks like carriers yeah. So it's really hard to find out if you got the right, shard yeah. So if you have a carrier system, you just take off the condenser panel.

You turn it around and right there. You have a chart that is very helpful indoor outdoor temperatures and you can just take a picture of that and use that, as a rule of thumb for any system. You work on you're going to have you're going to have pretty close pressures across systems. You can find it in a service manual for train.

They will either have an install or an additional service manual. They'll have something for your heat mode pressures. Basically, what it said is remove the chart and weigh it in yeah, which is which is they want? You just to do it right, yeah, which you talk about heat mode. Why we use rules of thumbs is because you can never really fully know if you're exactly where you should be.

I mean i've used a heat chart before on train, but maybe the model you had you couldn't find it in the install manual. I looked yeah. You can use these rules of thumbs or even look at a chart, maybe from a carrier and match the ton engine. Yeah see if you're close, you know a rude rheem linux, train or new carriers are going to be using a txv and txv problems.

You're going to make high pressure on one side and low pressure on the other yeah well, two inches. He had. He set up thermostat himself, mm-hmm for so yeah, okay and then, when i turned it on that tsp yeah yeah. So it went on low pressure instead of going out on high pressure right and that's the most common thing i mean.

If, if you're overcharged, then you could sometimes see a txv, that's slamming down go out on high head, but most of the time it'll go out on low pressure before it goes out on high pressure, and you can always turn the system into cool mode. Get the refrigerant moving backwards to find out if we still have um zero psi or really low psi intersection. You know kind of help confirm to you that it is a txv issue, because now we're using a different txt when you're running in cool than you are in heat. One of them is not working switch modes and just compare pressures in the other mode.

You can usually see oh wow, there's a really big difference in cool mode on my suction line, so i don't think this is low refrigerant. I think this is a closed txv on my heat side. Again, if your refrigerant pressures aren't going to be perfect, we didn't really talk about it, but you can use the method of covering and blocking the condenser coil sides to bring the head pressure up on the condenser coil and so like it's an easier way to find Out, if you're, actually, where you should be in cool mode, so if you bring your, you cover the outside of your condenser coils and you bring your head pressure up to where your saturation is more normal for what it would be in the summer. You see in a saturation in the 80s or the 90s, then uh.

That makes it a little bit easier for you to see if you're accurately, you know you have accurate charge and cool mode and probably even a better way to add refrigerant. I use that a lot this time of year just to confirm things like failed txvs and if i'm actually really low on refrigerant, and if you are that high pressure won't come out right. Yep you're not going to get your head pressure up there with the discharge temperature. I forgot to mention, but it's counterintuitive, if you're low on refrigerant you're, going to be actually above the 110 degrees, so you're going to have a much warmer line and the reason is because the compressor is still smashing to that exact point.

You have the force of the compressor smashing and if you have more refrigerant in there, it can only smash down so much and then, if you have less refrigerant in there, the molecules can actually be more compressed. Even though there's less molecules in there they're moving much faster they're, actually higher temperature you'll have a higher temperature discharge line when you're low refrigerant and if you're overcharged you'll have lower than 100 degrees above outdoor temperature. Unless it gets really extreme and you have really extreme overcharge, then you start seeing your pressures, your temperatures coming up on the discharge, if you're just slightly out of where you should be in your charge, that's the way you're going to know you have a hotter than Normal discharge, then you are undercharged you're colder than normal discharge. Then you are overcharged and that hotter lie and you're, like oh great that'll heat the house even better, but there's less refrigerant there.

So as soon as it hits your coil and the cold air starts going over it, it instantly becomes the temperature of the air because there's less refrigerant there there's less actual heat. So, even though it came in hotter and in cool mode, you notice it like when you are low on refrigerant, you notice that it starts freezing your saturation is in the 20s and it starts freezing right after that txv or piston. It feels like. Oh, this should be cooling better because my saturation, my coil temperature, is actually 20., but it's only 20 for a few inches of that coil.

There's such little amount of refrigerant. Coming into that into that coil. When the warm air hits it, it immediately changes that temperature from 20 degrees up to whatever the air temperature is thinking about the volume of refrigerant and how much heat transfer is related to that. Just keep in your mind that if you are warmer than 100 110 above outdoor temperature, then you are low on refrigerant and colder than you have probably have too much so right now, uh, one thing that me and austin found on maintenance was in heat mode.

It uses less refrigerant, so it looked normal, but when we cleaned the drain it was full of oil, went in and found a pretty large leak as well. Okay, yeah yeah, so pumping those drains yeah so on. Maintenance is when you can be checking cool mode and making sure that that looks good too this time of year. Don't only just check heat mode if you're doing a maintenance, wrap the condenser and just make sure your cool mode is functioning, can be pretty hard to see if it's exact but yeah, that's good.

So why why? Why would your system use less refrigerant in heat mode? Like why does it need less yeah? So liquid is where a majority of the liquid portion of your system is where a majority of your refrigerant is right, like your vapor can take a lot of space, but there's not a lot of there's, not a lot of refrigerant in that space, when it's liquid, You have a condensed version of refrigerant. You have all of your refrigerant there, so if you're in cool mode and you're overcharged that liquid is circulating through the outside coils, which is a massive area, and you can store a lot more liquid extra unused liquid inside that large condenser. But in heat mode, your liquid is this coil, it's a lot smaller! So if you're overcharged, that coil gets packed full, pretty quick and there's just not a lot to work with after that, and so overcharge will show up a lot more extreme in heat mode and can cause a lot of problems. Yeah we've had a lot of overcharged calls, especially on ductless repairs.

Yeah ductless are really extreme in that way. What were you saying that the numbers are compared like a normal system? It's like uses, i think they were saying it was like 30 40 yeah, like less yeah, less used refrigerant than a typical system, thanks for watching our video, if you enjoyed it and got something out of it, if you wouldn't mind hitting the thumbs up button to Like the video subscribe to the channel and click, the notifications bell to be notified when new videos come out, hvac school is far more than a youtube channel. You can find out more by going to hvacrschool.com, which is our website and hub for all of our content, including tech tips, videos, podcasts and so much more. You can also subscribe to the podcast on any podcast app of your choosing.

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