I have brian with hvac school podcast and hvac our school comm. I want to talk to you today about pressure temperature relationships and four years technicians would need something called a PP chart. Bd chart is a chart kind of like this one right here. That shows you.

The pressure and temperature relationships of various refrigerants, and specifically the refrigerant that you're looking for so for this particular one we're looking for our 407 C. So if you want to find the particular PT listing for a particular type of refrigerant, you go and you find the temperature and then that will give you the corresponding saturation pressure and vice-versa, you find the pressure it will give you the corresponding saturation temperature. The problem is nowadays there's so many different refrigerants they're changing so quickly. It's not only do you have the PT relationships at saturation, like you used to with all the older refrigerants now with modern blends, even refrigerants, like our 407 C, which is getting more and more popular, you have what's called dew point and bubble point, which is something You didn't use to have to deal with before what it comes down to is the refrigerant slider app is just a great free tool for you to use, and it replaces what a PG chart used to be if you're lucky and you have a good set of Digital gauges, you program the refrigerant engineer, ages and you'll.

Have it right there, but in many cases you're going to find yourself in a situation where you don't actually have the data you can go into the refrigerant slider, app and you'll have all the modern refrigerants, including Naturals like co2. So, in order to show what's so advantageous about the refrigerants slider app, I want to first show you sort of what an old-school PT chart looks like and what a PT chart even does. So what a PT chart is for is so that you can track your saturated state, so saturated refrigerant state had given pressures and temperatures. So if refrigerant is in the process of boiling or if in the in the process of condensing at a given pressure, we can know what the temperature is going to be or if we know the temperature we can know whether or not it is fully boiled fully.

Condense, that's what super eating sub cool are. So when we calculate superheat we're saying this is the temperature above boiling. Therefore, we know that it's fully vapor - and this is how much sensible heats been picked up past the point of fully boiling off and sub cooling is the opposite. We know it's fully liquid because here's how much temperature it's dropped past the point of fully condensing, and so we can use a PT chart to figure out all these things.

So let's do a really common one. Let's say we have a 75 degree turn air temperature and we have a design temperature difference on an evaporator coil of 35, which is very common for 400 CFM per ton. That would be a 40 degree saturated coil. So if the coil is boiling refrigerant in it at 40 degrees, so if I go to our 22 I track over from 40.

You can see that sixty eight point six degrees Fahrenheit. Now that doesn't take into account - or I should say it does already take into account 14.7 PSI, which is the pressure on the atmosphere already so PSI a would be. Sixteen point six plus fourteen point: seven, the fourteen point: seven is already subtracted out to calculate for the atmospheric pressure. So when we're looking at a PT chart or a gauge, that's already accounted for, but it's important to know, especially when you're working at elevation, because 14.7 PSI a only applied at sea level.

So let's look at another thing, so let's say we have a 1480 system and we want to calculate the condensing temperature over ambient and it's a 75 degree day and let's say we set a condensing temperature over ambient on this particular system is 20 degrees, which would Be common for like a 13 to 14 seer system, so if you have a 75 degree day plus 20, that would be 95, so you go down to 95. If you look across 95, where it hits for 10, a you can see: that's 295. So, on a 75 degree day with a 13 14 seer system, it would be common to see a 295 degree condensing temperature, and so we calculate our condensing temperature over ambient. We took our ambient added.

The 20 got our 95 and then calculated that on an R for 10, a system that would be a normal pressure that you would see. So it's really handy to have a PT chart, because once you start making these pressure temperature correlations, it doesn't matter so much. What refrigerant you have it matters to the design of the piece of equipment that you're working on, and then you need to know the pressure temperature relationships, but a piece of paper like this is extremely clumsy to keep with you at all times I mean when I First started in the trade I actually used to keep a PT chart in my pocket. The refrigerant slider ad makes it far easier and gives you far more information, especially when you start thinking about doing bubble points.

So there are several different ways that you can get the refrigerant slider app. I have an iPhone so so I'm going to search in the App Store. So I'm going to look up. You can do a lot of different things, but we can just look up Danfoss that'll be an easy way to do it and then you'll see the refrigerant slider app right here.

So we're going to hit open and now we're on the refrigerant slider app. You could also go to your browser of choice and type in Danfoss dot-com forward, slash cool apps, and then that will take you here to all of the different apps and the Danfoss toolbox. So we're looking for refrigerant slider, so we're going to go ahead and choose the iTunes Store, since I already have it downloaded. All I have to do is hit open.

So I want to show you some nice things about this. Let's start with our 22, you can save refrigerants as favorites, just by checking them like this and then they'll show up quicker I'll show up at the top of the list. So let's show some some common things that you would use a PT chart for and how this app is really superior to any PT chart that you've that you've used. So I'm just putting placing my thumb over this slider right now and moving it back and forth.

So let's say we want to have a target coil temperature of 40 degrees with our 22. That would be sixty eight point, eight seven psi or if I want to just enter in, I can just enter 40 degrees in, and it will also give me the result. Let's say I want to target evaporator temperature of 50 degrees. That's 84 point one eight! Let's say that I'm looking for, as I know, my outdoor temperature and I'm going up to an hour twenty two system and I'm looking for a condensing temperature over ambient of 20 degrees - and let's say it's 90 degrees outside, so that would be 110 degrees.

So we're going to go up here to 110 degrees, I'm just sliding there that's about 222 psi on an r22 system or I can just click the temperature and enter a 110. It's going to give me 224 psi. Let's look at a different refrigerant: let's go to r410a now we can do the same thing with r410a. Let's say we have the same circumstance.

We want to go to 110 degrees, that's about 364 or if I want to enter it in, I can go 110 degrees. 360 8.29 would give me that condensing temperature over ambient that I'm looking for 20 degree condensing temperature or ambient on a 90 degree day. You also have some additional data down here on the bottom right. It shows you the the global warming potential, which is the GWP.

The ozone depletion potential, which is zero on r410a, gives you the critical temperature, as well as the boiling temperature at zero psi G. So that's the point link temperature at atmospheric. If you click the arrow, you can get the chemical blend name, some additional information, the type of oil. The class of refrigerants is an HF C.

You also have the opportunity to hit, do or bubble point, and let me talk briefly about what do in bubble. Point. Are so this is doing bubble point where you can select dew point is the point at which the first drop of condensation will occur in a vapor bubble. Point is the first drop of vapor or the first bit of vapor that will occur in a liquid.

So there's actually a little bit of a curve there for 10a, it's very, very minor, so there's a very minor change. You see when I switch back and forth. It's only changing by 0.1 degree with the pressure at the same point. But if we look at our version, say are 407 C, for example, let's see if we can find our 4/7 see here now.

It's like there are 4 s. 7C now watch the difference when I change from bubble to do on our 407 C. Let's go to a temperature of let's look at a coil temperature, for example: 40 degrees. You see that you see the significant change that occurs when I switch between Dew and bubble and that's because it has glide what we call temperature glide and so depending on whether or not you're, calculating superheat or sub cool you're, going to use either dew point or Bubble so in calculating sub cooling you're going to use the bubble pressure.

So if I was calculating sub cooling, I'd be using bubble here on our 4 7c. So let's say that I had a a let's go up and we have a hundred degree. So 225 psi hundred degree Fahrenheit. Let's say I had a 90 degree liquid line temperature that would be 10 degrees sub cooling.

At this point, because I'm on bubble, you can see if I calculate it based on do, I would get a radically different result in my in my pressure temperature relationship and I would get an incorrect result, you can see. We have 9 degrees differential now between what I was reading in bubble and what I'm now reading do. So, if you get your do in your bubble, confused then you're going to have a significant problem. The opposite is true: when you're calculating superheat, so when you're calculating superheat, you would use do, and so let's say I have a 40 degree we're going to go ahead and and enter a 40 degree evaporator temperature.

That would be sixty three point: two seven psi. On 407 C system, and that would mean that I would have a 50 degree section line temperature at the outlet of the evaporator coil would be a 10 degree superheat. If I accidentally did it on Bubble. Instead of do you can see, it gives me once again a radically different result in the outcome.

So you need to make sure that you're, using the dew setting when you're calculating superheat when you're calculating the outlet of the evaporator and you would use the bubble. Setting when you're, calculating sub cooling and again the refrigerant slider app, makes it very very easy to do. In comparison to some of the other products out there, you can easily switch between Celsius and Fahrenheit. You can easily change the pressure readings from psi to other pressure scales, and it just makes it very easy.

You can also switch between absolute scale, which calculates in your atmospheric pressure, 14.7 PSI a at sea level, or you can use your gauge pressure, which already has that calculated in all in all the refrigerant slider app has all of the common refrigerants that you're going to Be using if you just look through this list here is an enormous list of refrigerants, including naturals and hydrocarbon refrigerants. It has all the refrigerants, including refrigerants, like our 290 propane. It has our 407 C, our 438, a our 422 and also has isobutane isopentane ammonia of many rare refrigerants that you're rarely going to run into and all of the all of the modern blends. All in all, the refrigerants slider app is a fantastic free application that I think any technician can use whether or not you're in refrigeration or air conditioning, especially as we're seeing the change in refrigerants.

This has been Brian from HVAC school thanks for watching.