Episode 273. CO2 Experts: Pipe Sizing with Chris Griffiths of Omega Solutions

Good flow. We need to have the least amount of pressure drops. We need to have oil coming back at all times. So our compressors are always lubricated. Components are lubricated. I'm excited about this because we're going to be diving into when there is piping problems. What do you need to do to fix them? Chris, welcome to CO2 experts. How you doing brother? Thanks

for having me, Trevor. It's nice to, nice to be on here. We've done some CO2 Mondays together in the past, and for those who know, we carry out a good number of design courses across the world together. So hopefully we can share some of our knowledge with you all today, ideally aimed at more of a practical on site perspective for pipe sizing, and ideally helping you solve some issues you may run into, versus how to design a system from scratch.

I know from my experience and training, when you're a technician on the tools, you don't get exposed to the reasons behind why a lot of the system is as it is in terms of design particularly with pipe sizing. And I know that when I made the jump from technician to design, there were not a lot of resources out there to be able to actually figure out how pipes were sized and if they were correct or not.

So hopefully from today, we should be able to give you a shortcut at least to get And help you along that journey as well.

This is one of the things that me and Chris talk about in our design course, because this is vital for designers as well as technicians. And when we were doing a design training, we talked to the designers about how to relay this information to contractors, to end users, because I think that's one of the most important thing as a designer, Chris, as we talked about before, is being able to communicate properly.

With your customers and piping is always one of the things that can either have a system run really, really well, or run into major issues either at the startup or down the road where people are like finding problems. And then it comes, it takes a while to figure that out. So that's, that's something that we definitely stress is making sure that pipe sizing is correct and then reviewing it with your team.

Thank you. Chris: Definitely. Everyone knows what looks good when it's installed. If it's nice and tidy, it's ID taped, insulation's all the way through, no tears. But in terms of that, if it's been sized correctly, is there an excess of the number of bends? Are they too short radius rather than long radius? If a pipe's too small, it's not going to carry enough refrigerant for it. If it's too big, not only have you spent loads more money on a pipe you don't need, it's also going to suffer in terms of getting the fluid flow for your oil back to your compressors.

We'll go into a bit more in depth in a moment, but these are the common issues I would see if I was designing a system or attending a site where they had issues These are the sort of things we can narrow it down to. So if we go through the list, we've got pipe diameter is too small, and in a more scientific term that means that we have insufficient mass flow through that system.

In most cases. If we don't have insufficient mass flow, what we will have though is excessive velocities because they're trying to shove as much of this refrigerant through in a tiny space. In one go, and that's going to cause a whole lots of issues, mainly it's going to wear the inside of that pipe surface away, which will then get carried over to your expansion devices back to your compressors, or sit in your oil sump, and if it's coming up to expansion devices, you're going to get liquid hammer as well on the liquid line, which is, as anyone's seen, if in your house, if you turn your faucet off too quickly, those pipes will shake, It's going to be the exact same in your refrigeration system.

In most cases. If we don't have insufficient mass flow, what we will have though is excessive velocities because they're trying to shove as much of this refrigerant through in a tiny space. In one go, and that's going to cause a whole lots of issues, mainly it's going to wear the inside of that pipe surface away, which will then get carried over to your expansion devices back to your compressors, or sit in your oil sump, and if it's coming up to expansion devices, you're going to get liquid hammer as well on the liquid line, which is, as anyone's seen, if in your house, if you turn your faucet off too quickly, those pipes will shake, It's going to be the exact same in your refrigeration system.

On the other end, if we have our pipes which are too large, mainly on the suction, we're going to have very poor oil return. We rely on that velocity in that suction, in that gas, to entrain oil from our evaporators if they've made its way to there, carry it all the way back to our compressors, and normally we're going to be working against gravity in some cases, so we need to make sure the velocity increases yet again when we're working against gravity to make sure it gets back to where we need it to.

If there are too many bends on our system, fluid flow is going to bounce into the corner of that and redirect. That's going to increase pressure, a pressure drop. Same with having too many or long, not long radius bends. And for those who are aware, the more pressure drop we have, particularly in the suction, the lower our evaporating temperature will be.

At our compressor, what our saturated suction temperature at our compressor will be. That increases the lift, what our compressor has to do, increases the compressor ratio, and uses more energy. More energy, more money. So save your customer some more money by making sure that pipe work is nicely designed.

At our compressor, what our saturated suction temperature at our compressor will be. That increases the lift, what our compressor has to do, increases the compressor ratio, and uses more energy. More energy, more money. So save your customer some more money by making sure that pipe work is nicely designed.

On our suction side, if we don't install oil traps on risers, We'll get poor heat exchanger performance because the oil will stay inside those evaporators, coats the surface a bit, and less heat transfer flows into the evaporator and reaches the refrigerant. And also eventually that oil will build up at that part of the system and eventually your compressors will be starved of oil.

And another one, less so as a design because we would, as a designer, assume that all the insulation is going to be installed correctly. But when you get to site, sometimes I've seen it that even though you specified One inch wall lagging. The installers have tried to save some money and gone for a slightly thinner wall.

Obviously that's a lot more heat buildup, more non useful soupy enters your section, but also you'll find sometimes if you're working with low temperature applications, it will start to sweat and you'll get condensation forming on the outside of that pipe. Again, leading to more issues, but in terms of system performance, sorry, traffic.

Obviously that's a lot more heat buildup, more non useful soupy enters your section, but also you'll find sometimes if you're working with low temperature applications, it will start to sweat and you'll get condensation forming on the outside of that pipe. Again, leading to more issues, but in terms of system performance, sorry, traffic. Go ahead.

So a lot of people think, well, I got insulation on it. It's not. Gathering any heat or it's not generating heat. Do you want to talk a little bit about that? Can a suction line pick up heat even though there's one inch insulation on it?

You could effectively double the amount of heat being added to that pipe because our temperature difference has gone from 20 degrees celsius up to a sort of 40 degrees celsius into our pipe work even more so if we're kind of working with low temperature. It's just a case of not just copy and paste from a previous design you've done, actually look at where that pipe is going to go and account for it as well.

You could effectively double the amount of heat being added to that pipe because our temperature difference has gone from 20 degrees celsius up to a sort of 40 degrees celsius into our pipe work even more so if we're kind of working with low temperature. It's just a case of not just copy and paste from a previous design you've done, actually look at where that pipe is going to go and account for it as well.

Like a lot of people ask me, well, Trevor, CO2, your, you know, your such as running at 400 PSI or 30, some you know, 25 bar, 30 bar. Why, why do we need traps in the suction line? Cause the pressure is so high. Do you want to elaborate a little bit on that? Even though it's serious.

In presentation, but just up front, it's more important when we operate at part loads. So, if we have one evaporator, absolutely fine, it's normally going to be on or off, or there'll be a slight drop in it when it's overnight. If we have a row of 10 cabinets, And eight of them are satisfied, but two still need cooling.

Lo and behold, there's a lot less mass flow to try and push that oil back up the riser. At which point, eventually, that riser will fill, but there'll be insufficient pressure behind it, or insufficient mass flow, and eventually those two cabinets will starve, because there's no, no fluid movement in that section.

And eventually we'll start to achieve hot, you know, high temperature alarms, alarming out. So hopefully part of this presentation should alert some technicians out there that if you're getting oil issues, it can well be due to the fact that an oil riser has not been installed correctly. Or at all. I love it. Yeah.

Let's jump on to the first one, which is what happens if we have pipes which are too small. So I think that's probably what most people are going to find, rather than the other side. If you want to cut costs when you're installing, you're probably going to look, oh, can we get away with a three quarter inch pipe there instead of a seven eighths, or an inch and one eighth instead of an inch and three eighths.

So, as we go through, there's quite a few issues that can occur from insufficiently sized pipes. So, number one, insufficient system capacity. If we're not getting that mass flow through, we're not going to generate as much cooling as we actually need, and therefore, we're not going to achieve temperature in our cabinets or our cold rooms.

So, as we go through, there's quite a few issues that can occur from insufficiently sized pipes. So, number one, insufficient system capacity. If we're not getting that mass flow through, we're not going to generate as much cooling as we actually need, and therefore, we're not going to achieve temperature in our cabinets or our cold rooms.

We're going to have excessive pressure drop, which, as we've already touched on, reduces our saturated suction temperature, leads to increased energy consumption in the compressors, and That there has a knock on effect with increased discharge temperatures, and it may be a case of then your condenser is undersized and you want your gas cooler in this case.

Particularly on an LT system, have we got an intercooler you know, some sort of intermediate rejector? Is that now going to be too hot to then go into our medium temperature compressors? And thereby increase the discharge temperature there and have that knock on effect. That then leads to oil issues.

Are oils going to be running too warm? And then that leads to compressor failure. And then on the other side, more of an issue with liquid lines, excessive noise and vibration, liquid hammer, and excessive wear on those internal pipe surfaces. So just to summarize on all those, if that pipe work is too small, some or all of those issues could be present.

Are oils going to be running too warm? And then that leads to compressor failure. And then on the other side, more of an issue with liquid lines, excessive noise and vibration, liquid hammer, and excessive wear on those internal pipe surfaces. So just to summarize on all those, if that pipe work is too small, some or all of those issues could be present.

If you're only getting one or two, the process would be to go through and find out or rule out the typical steps you would do, you know, are our compressors working? Have we got oil in them? Etc. If we add oil to a system and then go back two weeks later and find, well, there's no oil in our reservoir, but there's no signs of signs of oil leakage anywhere across the system.

And we also find actually only a handful of fixtures are not achieving temperature rather than all of them. It may be a case that oil is being trapped somewhere. And then we have to look back at this, this side of things. So what we're going to do in a second, it's going to get quite technical, we're going to look at MT only pipework analysis on a dual temperature rack using appropriately sized pipework versus incorrectly sized pipework.

So we're going to look at the correct application, it's only a small one so we're literally looking at half inch pipe. And then we're going to look at what happens if it was only three eighths pipe. And then we'll also have a look what if it's five eighths pipe and slightly too large. That's a lot of numbers.

So we're going to look at the correct application, it's only a small one so we're literally looking at half inch pipe. And then we're going to look at what happens if it was only three eighths pipe. And then we'll also have a look what if it's five eighths pipe and slightly too large. That's a lot of numbers.

I'm just bracing you all now. Stand by. Just seen a question in the chat, Trevor, as well. So pipes outside diameter is going to be the same size as the next. Some pipes are thicker to handle more pressure. This is something we have to be aware of. Yes. So if we're looking at, for example, starting at standard.

Gauge copper pipe versus K65 where K65 will be a thicker wall. Yes, there will be a difference in capacity. On that flow. So most of the softwares out there will take that into account because each each pipe work will have its own internal roughness factor, and an actual usable cross sectional area. And then, next question.

What about compressor piping so Carrier recommends inverter traps all compressor sections due to liquid migration, but hadn't seen this in the field from an OEM build yet. So. Is that looking more, I believe that's looking more component manufacturing, which is a bit beyond the scope of this as a technician side of things.

What about compressor piping so Carrier recommends inverter traps all compressor sections due to liquid migration, but hadn't seen this in the field from an OEM build yet. So. Is that looking more, I believe that's looking more component manufacturing, which is a bit beyond the scope of this as a technician side of things. Should we tackle that one at the end? We'll

So, we've got a small system, which I'll show you shortly in terms of how it, how it all combines, but we've looked at a section of pipework, we've used Danfoss Cool Selector 2 for this, and we've And bits as software as well. So the idea of this is we'll look at this pipe size and then see what impact that has on our compressor selection and what our coefficient of performance would be as well.

So we've selected a half inch pipe and the key item we want to look out there is this highlighted red box, just Delta T saturation, temperature, and Kelvin. So that is the equivalent temperature for our pressure drop in that pipe. So what this means. Is that 1. 1? At our compressors, the saturated suction temperature will be 1.

So we've selected a half inch pipe and the key item we want to look out there is this highlighted red box, just Delta T saturation, temperature, and Kelvin. So that is the equivalent temperature for our pressure drop in that pipe. So what this means. Is that 1. 1? At our compressors, the saturated suction temperature will be 1.

1 Kelvin lower than what our evaporating temperature is on our lowest temperature suction lowest temperature evaporator on that suction pipe. So say we have a meat counter in a deli area, and that's evaporating at minus 10 Celsius. This would be 1. 1 Kelvin lower than that, which means we'd be evaporating at minus 11. 1.

Or in this, if we were evaporating at minus 6 Celsius, it'd be minus 7. 1. And I always bother to travel with this, but I don't know the conversion factor off the top of my head to Fahrenheit. I want to say it's around 14 or 12 Fahrenheit. I'm sure someone can correct me on that.

bits of compressors. We've got a single low temperature compressor and two LSL 1K and two medium temp, two KTE 5Ks. Just put some design parameters in. Low temp is evaporating at minus 30 Celsius, which minus 22 Fahrenheit. We've got a small amount of useful evaporator soup heat, and then 15 Kelvin of non useful soup heat, which is what it picks up in our suction line.

And then the same again on our medium temperature as well. And then we've got a gas cooler outlet temperature of 37 Celsius and an intermediate pressure in our receiver of 38 bar. More importantly, what that gives us are these key values again, highlighted in red. Our evaporator capacity, our power input, and our discharge temperature, without any additional cooling.

So we've got a COP of 1. 43 there. It's not too bad, it's not great, but this is peak condition, I don't mind. Let's see what happens if we had a 3x pipe instead. Well from this you'll see actually that pressure 1. 1k equivalent to 5. 4. And

what that does, immediately it drops our evaporator capacity down to 12. 2. Our power input stayed roughly the same, slightly up, and our discharge temperature has gone up by about 10 Celsius. And our COP has gone down from 1. 43 down to 1. 28. So just by changing the size of that pipe, we've had a very large impact on our system's performance.

what that does, immediately it drops our evaporator capacity down to 12. 2. Our power input stayed roughly the same, slightly up, and our discharge temperature has gone up by about 10 Celsius. And our COP has gone down from 1. 43 down to 1. 28. So just by changing the size of that pipe, we've had a very large impact on our system's performance.

And this is how important it can be. Most importantly for me, I would see that discharge temperatures gone down quite considerably. That's where you may start to run into real issues on site with your oil management.

So that looks horrible for a technician to try and carry out in the field. You would need a laptop or a very capable smartphone. Yeah, what can we do instead? Well, there's not a lot we can do in the field. If you're up against a problem like this, you need to start jotting some information down, and then doing some homework.

So, unless you can see, immediately, if you go from a 5 8 pipe down to a 3 8 pipe and back up to a 5 8 pipe, well, there's obviously going to be some sort of restriction, excessive pressure drop there. But what do we have to do instead? Well, we need to do some good old fashioned starter level engineering.

So, unless you can see, immediately, if you go from a 5 8 pipe down to a 3 8 pipe and back up to a 5 8 pipe, well, there's obviously going to be some sort of restriction, excessive pressure drop there. But what do we have to do instead? Well, we need to do some good old fashioned starter level engineering.

So we go back to basics and we carry out the heat load calculations on our system. Hopefully you don't have to do this from first principles. You should be able to find the information from the manufacturers of what's been installed on site already. So we have, if we know exactly what evaporators are in our cold rooms, we can find the manufacturer's data sheets for that, for example, on the right hand side, I've used a Kelvin cooler, which I would have used quite a lot in the past, a Casey MX 40 dash six.

And we know that can do 4. 2 kilowatts, uh, whatever conditions we said minus six or 10 or minus seven with an eight K. Delta T on it. And then we'll have a look for these display cabinets as well. So on here, there's two, which I've selected for our system. We've got a six foot and a 12 foot cabinet, and that's at three and six kilowatts respectively.

And then the fun part happens where you have to sketch out and trace every bit of pipework feeding back to that system. Well if you're in a supermarket, hopefully it's a large one, you can just point in the ceiling and trace it through. Or you might be in a small convenience store where it goes through three extra retail units, down into a basement, under someone's garden and pops back up in a machinery room elsewhere.

And then the fun part happens where you have to sketch out and trace every bit of pipework feeding back to that system. Well if you're in a supermarket, hopefully it's a large one, you can just point in the ceiling and trace it through. Or you might be in a small convenience store where it goes through three extra retail units, down into a basement, under someone's garden and pops back up in a machinery room elsewhere.

It could all be quite a bit of fun. From that, no down move sizes. Take account of as many bends as you can and then we'll start trying to populate into some software. So the Danfoss one I like to use in demonstrations of these because it is free, it's accessible most places in the world, although it's very slow to do large systems.

There are paid softwares such as Whiterose Micropipe, which is excellent for this and you could analyze a system in probably 20 minutes if you became proficient with it, but it is a paid subscription. But if you encounter one of these issues and you fix it, it's probably well worth purchase. And once you've got all that, to check if you're having issues with the compressors, put that information into your compressor software, and see if it puts them out of our operating ranges.

There are paid softwares such as Whiterose Micropipe, which is excellent for this and you could analyze a system in probably 20 minutes if you became proficient with it, but it is a paid subscription. But if you encounter one of these issues and you fix it, it's probably well worth purchase. And once you've got all that, to check if you're having issues with the compressors, put that information into your compressor software, and see if it puts them out of our operating ranges.

Let's say we've traced all that pipework. Here we go. We've got two display cabinets and a single cold room. Nice, easy, simple system. And for the purpose of this, let's assume that all three fixtures are not maintaining temperature. We've already weighed out the refrigerant charge, we've already checked oil, we've checked that ambient conditions are okay.

Yeah, it's not outside of its peak. designer envelope. The idea that you'd have a operations and maintenance manual on site, and you can check back to that for the initial design, but I'm sure many of us can attest about when you actually need one, they're never to be seen. Especially at two o'clock in the morning when you've got a store shouting and screaming at you to get their systems back online.

So what we'll do, if we assume that all three cabinets are in place, Well, the only thing shared between all three there is that main run from that last point back to our compressors So let's look there to begin with and we can start to model that section in a bit more detail as well So Dan Foss allows you to put each individual section of that pipe into play So we can start with a horizontal section followed by a 90 degree bend another 90 degree bend So that'd be for a bottom of our riser A vertical section, top section, where it tops out, horizontal, comes down, along, down, along, etc.

So what we'll do, if we assume that all three cabinets are in place, Well, the only thing shared between all three there is that main run from that last point back to our compressors So let's look there to begin with and we can start to model that section in a bit more detail as well So Dan Foss allows you to put each individual section of that pipe into play So we can start with a horizontal section followed by a 90 degree bend another 90 degree bend So that'd be for a bottom of our riser A vertical section, top section, where it tops out, horizontal, comes down, along, down, along, etc.

And based on half inch pipe, this gives us a total pressure drop of 1. 1 as we looked at earlier. How easy is that? For doing this, we'd populate as much of the information as we could. If you don't know this on site, ideally it should be designed to be sorts of levels, so we're looking forward to it.

Between 5 and 8k useful superheat, which is what's inside your evaporator. Assuming we have electronic expansion valves which can sort of maintain that target. And then additional superheat, we try and go between 15 and 20. Some people would go up to 30 Kelvin, which would be 50 Fahrenheit. For additional soup heat and by that we mean non usual soup heat.

Between 5 and 8k useful superheat, which is what's inside your evaporator. Assuming we have electronic expansion valves which can sort of maintain that target. And then additional superheat, we try and go between 15 and 20. Some people would go up to 30 Kelvin, which would be 50 Fahrenheit. For additional soup heat and by that we mean non usual soup heat. So that heat, which we pick up in that suction pipe work through the insulation

and then on our Which can be good for, for CO2 compressors, because we know CO2 compressors, especially the low temp ones need higher superheat than a standard HFC compressor. So sometimes that can play to your benefit in your design, but we see more and more designs with either plate heat exchangers to protect them, that extra protection for those compressors. Thanks. Yeah,

Yeah. And then you got to size accordingly to that because you might have the best pipe sizing, but if you make a mistake on the, that plate heat exchanger or something that's going in there, that's going to mess up your pressure drop. For components. Yeah. Chris: So here we go. We've got our value there. But again, that's what, what, what happens now if we go for three x pipe instead and lo and behold that 1.1 has become 5.2. So from that we could effectively guarantee that is an issue with that pipe size.

Just you has Yep. Someone's already jumping ahead of us in the chat here with what to do next. So what if we had five eights instead of three eights or half inch? Here we go. So let's go three quarter. Let's say they've massively, possibly oversized there. Well, that saturation temperature, similar towards the bottom right, is no longer an issue.

And we have very minimal pressure drop here. 0. 1 Kelvin, 0. 2 Fahrenheit. But what we do have now is potentially too low a velocity up our riser. So a rule of thumb previously that people have worked with is you drop your riser size on the vertical over one to two sizes below your horizontal. CO2 is a bit more forgiving than HFC in terms of carrying oil back to a compressor.

And we have very minimal pressure drop here. 0. 1 Kelvin, 0. 2 Fahrenheit. But what we do have now is potentially too low a velocity up our riser. So a rule of thumb previously that people have worked with is you drop your riser size on the vertical over one to two sizes below your horizontal. CO2 is a bit more forgiving than HFC in terms of carrying oil back to a compressor.

Often find we need to step it down. I've designed a lot of stores out there where, yeah, you've not needed to whatsoever. But then sometimes you fall into the risk of people getting complacent and thinking, oh, because we didn't do it on that site and didn't do it on that site, well, we don't need to for this one. Despite what the design drawings say. And then they'll put the same pipe size in and then wonder why at part load conditions all those cabinets on

that island start to fall over sideways. Yeah, not naming any names, that's fine. There's always some fun arguments of that on site. But that's being important to the detail, right, Chris, like not, like you said, not being complacent in it because it can get repetitive what we do as a technician, as a designer, as an engineer, because we see it day in, sometimes day in and day out in your role.

And sometimes you can get complacent because I know I've done it before. So it's important to look at those fine details on projects because not all projects are going to be the same things will change sometimes, even in the design. I've seen this happen multiple times where this was, I remember this one time where we were designing a store and we looked at the prints and there was three feet of a case over a walk, a door, you know what I mean?

And sometimes you can get complacent because I know I've done it before. So it's important to look at those fine details on projects because not all projects are going to be the same things will change sometimes, even in the design. I've seen this happen multiple times where this was, I remember this one time where we were designing a store and we looked at the prints and there was three feet of a case over a walk, a door, you know what I mean?

So it was like. Place on the map wrong on the store map, like doing the install. So things sometimes have to change or there's a revision before the store starts and you don't have the right documents. As well as don't change the pipe sizing. If you're a technician, don't just go ahead and change. Oh, just like Chris says, Oh, well, last time it was inch and three.

Let's just go inch and five. That'll be a bit better. Because I've had people reach out to me and say, well, the foreman said, let's go with Inch and five eight because that's what he did in the last store but didn't take into account that it was a hundred feet less Or you know what I mean? And then all of a sudden now there's oil issues and that's that's where you gotta get into these softwares

what i've noticed even the The best intentions for customers to make sure every store looks the same and the sales floor may look identical But back of house and in the warehouse areas cold rooms completely different And almost always you'll have something different.

I, I was waiting for at least one day where I could remember back to one, one design I've done and just copy and paste at least the pipe sizing. But it never came. Hundreds and hundreds of stores and designs. Not one matches another. And these are in fairly standardized. stores for a customer. I can't imagine trying to do it in some of the less standardized stores across other estates.

It will effectively change all the design or at least notify you what pipes now are undersized, oversized, things like that. So that's the difference between like micropipe and like cool selector two or another sizing software out there. Great question, William.

It will effectively change all the design or at least notify you what pipes now are undersized, oversized, things like that. So that's the difference between like micropipe and like cool selector two or another sizing software out there. Great question, William.

It's a very iterative. method in issue of some good software for it. So if we look back to this, we would have a pipe section coming off of that cabinet, off of this one, and then they join together and then they meet this one for the evaporator here, and then you have this section here. And whilst only five, probably six sections we'd have to model, if we change the size on one of those, because we found actually that one size is insufficient, that will change all the characteristics of each other section of pipework, because.

The pressure drop over all has changed. It may impact the velocities in other areas. It may impact the mass flow in other areas. So it's. It can be quite a repetitive task. It's okay for systems that up to, I was going to say up to sort of six fixtures. Depends how patient you are. You can do a hundred fixtures in an 80, 000 square foot store.

The pressure drop over all has changed. It may impact the velocities in other areas. It may impact the mass flow in other areas. So it's. It can be quite a repetitive task. It's okay for systems that up to, I was going to say up to sort of six fixtures. Depends how patient you are. You can do a hundred fixtures in an 80, 000 square foot store.

I wouldn't want to, but you could, but it's also that time of having five working days dedicated to doing that. And then when a revision comes through, potentially doing it all again. Yeah, it's how, how patient you are and how quick you are identifying similarities and rules of thumb. So going back to this, let's say for example we found that our pipe size between the evaporator there and the condensate was 3 8's.

And that could well happen on site because the suctions between those two cabinets, the 12 foot, may only be a 3 8's suction. And then it may be a 3 8's suction coming off of that evaporator. And then people may assume well because they're all 3 8's we can continue with that. But actually no, now you've got additional mass flow coming from that evaporator and then we need to step it up in size.

Another way to check if that's too small, or too low, is we could go actually measure our suction pressure of a compressor, and check it's, you know, say it's 24. 7 bar gauge or 360 psi. Well if we know what evaporating pressure is at our evaporators, and when we can compare that to the difference, if it's drastically lower, It probably is a restriction, I say a restriction undersized pipe.

Another way to check if that's too small, or too low, is we could go actually measure our suction pressure of a compressor, and check it's, you know, say it's 24. 7 bar gauge or 360 psi. Well if we know what evaporating pressure is at our evaporators, and when we can compare that to the difference, if it's drastically lower, It probably is a restriction, I say a restriction undersized pipe. 'cause we're now getting excessive pressure control.

You know, they're running into oil issues and that's how big of a pressure drop they have in their suction line going back to their condensing unit or to that yeah, to the condensing unit. So it's something that it's, and that's a quick check. Like you can go in and now today with CO2 systems, we've got pressure transducers on almost all the evaporators. Well, we do have them on all of the evaporators, so you can compare that to your suction header pressure.

quite drastic. When you say one bar, you know, 15 PSI pressure drop, that HFC system. Well, you don't got any chance of yeah, your compressor's running accordingly there. You know, if you're on a low temp 404A system, you'd be running nearly in a vacuum at that point.

Got two questions here just before we move on to the next slide. Fitting quantities normally counted during design or an allotted percentage estimated during design and then the actual quantities counted when the project is being installed to assure we are staying within the design criteria. Yes, so there's two ways I've seen of this generally is you multiply your pressure drop by, say, an additional 15 percent to account for that as a rule of thumb.

Or, if you have a software and you input a target pressure drop of, say, 2 Kelvin on the sectional 1. 5 Kelvin, you then set that at a level low enough that actually, in reality, it might be slightly more than that. But at least you know that your pipe sizes aren't going to Drop your saturated suction temperature below what it needs to be so a good rule of thumb or I say a good rule of thumb The bare minimum I would say is a two Kelvin pressure drop should be three point three point six Fahrenheit that should be the most pressure drop you really get because at that point you're getting yeah You're throwing money away in terms of reducing the efficiency of your compressors But if you try and design all your stuff around half of that value, or 75 percent of it, and don't factor in any of your bends or fittings, et cetera, any of that which does actually occur in real life, you haven't had to model, but you can be fairly confident it won't drop it below what your actual saturated suction temperature needs to be.

Or, if you have a software and you input a target pressure drop of, say, 2 Kelvin on the sectional 1. 5 Kelvin, you then set that at a level low enough that actually, in reality, it might be slightly more than that. But at least you know that your pipe sizes aren't going to Drop your saturated suction temperature below what it needs to be so a good rule of thumb or I say a good rule of thumb The bare minimum I would say is a two Kelvin pressure drop should be three point three point six Fahrenheit that should be the most pressure drop you really get because at that point you're getting yeah You're throwing money away in terms of reducing the efficiency of your compressors But if you try and design all your stuff around half of that value, or 75 percent of it, and don't factor in any of your bends or fittings, et cetera, any of that which does actually occur in real life, you haven't had to model, but you can be fairly confident it won't drop it below what your actual saturated suction temperature needs to be.

And then following on from that, another question, is it good practice for a fast calculation to use the piping module in CoolSelector instead of components in series? Yes, definitely. Based on what we've just said, as long as you allow a little bit extra leeway on your, to overall pressure drop, we can assume that we don't have to model this 90 degree bend here, here, here. And I'll just slide back to,

Even better. So what our solution for this would be if we had that as in, as 3 eighths inch, we'd increase the pipe size. I imagine 90 percent of people out there, technicians, would come to that same conclusion as well. If it's too small, you make it bigger, up you go.

Maybe it's an electrical issue. But sometimes design mistakes happen. Complain and, and, you know, cry about it. We got to fix it. This is, this is it. Nobody's there, but you, at the end of the day, it's you that has to fix it as a technician. And it's important to, to learn this stuff. I think I am a better technician now is because I'm learning design and engineering behind why something happens.

Maybe it's an electrical issue. But sometimes design mistakes happen. Complain and, and, you know, cry about it. We got to fix it. This is, this is it. Nobody's there, but you, at the end of the day, it's you that has to fix it as a technician. And it's important to, to learn this stuff. I think I am a better technician now is because I'm learning design and engineering behind why something happens.

If you're running into an oil issue, there's a reason why don't just keep adding oil, like Chris said earlier, we got to figure out why the oil is gone. If it leaves. And doesn't come back. It's somewhere in the system, unless there's a leak, that's your first step. And that's usually obvious. Sometimes it's not if it's in the attic or on top of a walk in box, but most of the time it would be obvious on a oil stain somewhere, but if you don't see any of that, that oil is still in the system somewhere.

Correctly, I would say we've added oil to the system recently, it's still in our compressors, a handful of cabinets are down at temperature and they're still not achieving temperature, whereas all the others have, it could well be a piping issue, could still be loads of oil trapped in that section of pipe work, down in those evaporators, coating them all, and basically the more oil we have down there, Less heat transfer we're going to get into our refrigerant because it just coats the surface of those evaporator coils.

Correctly, I would say we've added oil to the system recently, it's still in our compressors, a handful of cabinets are down at temperature and they're still not achieving temperature, whereas all the others have, it could well be a piping issue, could still be loads of oil trapped in that section of pipe work, down in those evaporators, coating them all, and basically the more oil we have down there, Less heat transfer we're going to get into our refrigerant because it just coats the surface of those evaporator coils.

You'd need to have twice the airflow to get the heat into it. Which, well, those, those lap fans aren't going to change. So all you're going to do is get half the cooling. And therefore it's not going to achieve temperature and then you'll get all of your alarms happening instead.

Another side of this is, is one fixture on a row not achieving temperature when the other fixtures are satisfied or if they're defrosting? Well, that could well be a case that oil is trapped inside that system or it's not being able to force its way back up our riser back to our suction pipe and carry on the flow.

So it could be well be a case that an oil riser is insufficiently sized or it's not present at all. So a bit about the design on these. We have a downward curve at the bottom. and an upward sweeping bend at the top. The bend at the top is so once oil makes its way up there it doesn't have a way to drop back down.

So it could be well be a case that an oil riser is insufficiently sized or it's not present at all. So a bit about the design on these. We have a downward curve at the bottom. and an upward sweeping bend at the top. The bend at the top is so once oil makes its way up there it doesn't have a way to drop back down.

Say it falls out or the mass flow drops and there's not as much refrigerant flowing through there, that's top section, but the oil's still sat in that pipe it could possibly work its way back down. Good practice is to design suction pipe work with a slight slope back to the compressors, or to the next point of the next oil riser.

The bottom section as the process carries on oil starts to fill up that trap and it will basically trap it trap trap trap until it reaches a point where it can no longer go through this seal. Let's say it makes a nice Flat oil trap as any trap below your sink in your kitchen, you know, you have water in there to stop smells coming back Well same principle here You know We want to make sure that gas builds up behind to us enough velocity to then dislodge that oil and force its way up Normally, we design this based on a certain velocity so with HFC you typically seen velocities of sort of 12 meters a second to 20 meters a second plus and You know, it should be 2, 400 feet per minute to 5, 000.

The bottom section as the process carries on oil starts to fill up that trap and it will basically trap it trap trap trap until it reaches a point where it can no longer go through this seal. Let's say it makes a nice Flat oil trap as any trap below your sink in your kitchen, you know, you have water in there to stop smells coming back Well same principle here You know We want to make sure that gas builds up behind to us enough velocity to then dislodge that oil and force its way up Normally, we design this based on a certain velocity so with HFC you typically seen velocities of sort of 12 meters a second to 20 meters a second plus and You know, it should be 2, 400 feet per minute to 5, 000.

CO2 is a lot more forgiving in a sense. You can get oil entrainment at much lower velocities because of the denser suction vapor in effect. It entrains oil very well. We've run some calculations. I mean, again, it's effectively two and a half meters a second lower than HFC to carry on that bit, to carry that oil up. I'll see that's depending

case by case, but almost as a rule of thumb, you can have velocities two to three meters a second lower, which would be 100 to 300 feet per minute lower as well. Or up to 600 feet per minute lower, sorry. Rule of thumb previously was to step riser size down by one size compared to horizontal sections and also other people I've ran across with quite a good rule of thumb up to three fixtures on a single riser above three we switch to this double riser configuration which is shown on my right hand side here and operates very similarly.

case by case, but almost as a rule of thumb, you can have velocities two to three meters a second lower, which would be 100 to 300 feet per minute lower as well. Or up to 600 feet per minute lower, sorry. Rule of thumb previously was to step riser size down by one size compared to horizontal sections and also other people I've ran across with quite a good rule of thumb up to three fixtures on a single riser above three we switch to this double riser configuration which is shown on my right hand side here and operates very similarly.

The oil riser still needs to be sized so it can accommodate full mass flow for those fixtures connected to it. But also be sized small enough that at low load, you know, say if we had a row of 10 cabinets, only two of them were running. Well, we need to only carry one fifth of the flow through it. Well, that might not be enough to return all that riser at low load, but if we sized it smaller, we'd have an excessive pressure drop here and have a negative impact on our system or at our compressors.

So what we can do is put this double riser in instead. This oil trap at the bottom will fill up, and if we only have one or two fixtures connected to it, What they'll do instead is find their way up through here. If we only have a handful of fixtures, we're not worried about oil returning at that time.

Once the rest of them turn back on, it'll flow back through that main route and it'll carry on as normal, but we still want that suction gas to rise up this point here. So why don't we do this on every system? It's a lot more pipe work. It's very difficult to make look tidy as well, which I know a lot of end users particularly Merchandising teams unless you have large boxing in you're going to have to look at what most people would see as a mess of pipes

Once the rest of them turn back on, it'll flow back through that main route and it'll carry on as normal, but we still want that suction gas to rise up this point here. So why don't we do this on every system? It's a lot more pipe work. It's very difficult to make look tidy as well, which I know a lot of end users particularly Merchandising teams unless you have large boxing in you're going to have to look at what most people would see as a mess of pipes

I think they look pretty good to be fair We don't see them very often in the UK CO2 systems. So when you do come across one possibly leftover HFC, it's quite a special thing to see. I just think it's a great engineering solution. So I only seen a few

Open fronted display cabinets on a single riser. You can get some large swings in duty there. If some of that temperature, if night blinds are down overnight, or some are on defrost, yeah. And you still need a decent amount of product being cooled in the grand scheme of things. It makes sense to go down this route here.

How can this ideally help you as a technician on site? Well, a couple of questions to ask yourself is. Has it been present since startup? Have you always suffered with this building? Have the store management say, well, it's been doing this since day one? They'll say that for everything, regardless if it's brand new or not.

But at least you might sometimes get a straight answer from them. If it is, yes, it's probably pipework related, or it may well be. But then, if it's not, has work recently taken place, which has changed that pipework? Have, have they moved some cabinets? Have they added some onto the system? Well, it could be an issue with duty, or it could be a case of now that island was there, now it's there.

But instead of connecting to that section of high level pipework, it's connected to that one, and that's two sizes too small now. Yeah. Ideally, you should have some isometric pipework schematics, and you might be able to trace them, but again, probably not. Some of these stores could be 15, 20 years old, but they're still having work done.

But instead of connecting to that section of high level pipework, it's connected to that one, and that's two sizes too small now. Yeah. Ideally, you should have some isometric pipework schematics, and you might be able to trace them, but again, probably not. Some of these stores could be 15, 20 years old, but they're still having work done.

Go back to these sort of first principles and, and almost common sense. Yeah, if something looks wrong, you'll probably know it from, from experience. Carry out your normal checks. So check your control settings, your pressures, your temperatures, your brunt current, the oil, liquid levels. Go back to what we spoke about earlier.

Check, check the evaporating temperature at some of the display cabinets. And then check it at the compressor. See how much of a difference there is. How much pressure drop is there. If it is an excessive amount, it's probably a pipe size issue. Or you'd have a restriction somewhere. You're not likely to get a restriction in a suction pipe. So it's probably the suction pipe itself is the issue.

One, one bar of fresh drop is only about one Kelvin equivalent temperature or two Fahrenheit. Whereas HFC, if you'd lost a whole, you know, one bar, 15 PSI on four and four, you change it from a medium temp system to a low temp system almost immediately. Yeah. So it's, it's known about refrigerant. Again, Danfoss is really helpful for this by their I think it's called RefTools.

Yeah, RefTools. Yeah. Excellent. It has a refrigerant slider, the comparator for any refrigerant you're realistically going to use out there. So you can go through, bookmark some of the preferred refrigerants if you work with them on a daily basis. I think I've still got 134A and 404 on there from whenever I came off the tools, you know, talking seven or eight years ago.

Yeah, RefTools. Yeah. Excellent. It has a refrigerant slider, the comparator for any refrigerant you're realistically going to use out there. So you can go through, bookmark some of the preferred refrigerants if you work with them on a daily basis. I think I've still got 134A and 404 on there from whenever I came off the tools, you know, talking seven or eight years ago.

I don't think there's probably a 404A system out there to work on nowadays, or hopefully not anyway. There's less and less going back for sure. Yeah. Excellent. Is the fault present across the entire system? If it is you can narrow your Scope down search from that Trace by what is the last fixture before it gets back to the compressor if you rule that out Well, you may not be pipe sizing or unless you've got excessive pressure drop from that point back again And then start breaking into sections as we do any fault finding you try and break one large piece down into smaller sections until you get To either that is the issue or you can rule that out so Again, ask yourself questions.

If yes, check the pipe sizes between the closest fixture and the compressors. If not, check the pipe sizes on just those fixtures which aren't achieving temperature. And sometimes the only way to be sure is to go back to first principles and design the system in line with best practices. But as a technician, you shouldn't be expected to do that.

If yes, check the pipe sizes between the closest fixture and the compressors. If not, check the pipe sizes on just those fixtures which aren't achieving temperature. And sometimes the only way to be sure is to go back to first principles and design the system in line with best practices. But as a technician, you shouldn't be expected to do that.

You should expect that those who've designed the job, signed off on it, installed it, did their due diligence and installed it. But there's always changes. As we've said, a brand new system. They have no excuse. If it's 20 years later and maybe someone else has come in, someone else come in, someone else come in, move some cabinets, change some controls, maybe messed up something.

It could well be pipe related. Just do your due diligence as a technician and just check it over. Rule out, at least, you know, that's not the issue. And then you can start getting back to look in what is it? One component I need to sort. Great. Is that an electrical fault? Great. And deal with that. You're not having to re pipe 30 feet worth of high level services.

You know, it can be a big, a big task to repair, which to be fair is why it requires some thorough investigation. So that brings us to the end of that one. Does anyone have any questions? We've had questions as we go along, but it's welcome anymore.

You know, it can be a big, a big task to repair, which to be fair is why it requires some thorough investigation. So that brings us to the end of that one. Does anyone have any questions? We've had questions as we go along, but it's welcome anymore.

They're getting different temperatures from that design. So now they're looking at it, that they're, they're not meeting capacity in the middle of the summertime because it's hotter summers than it was when they designed it the first time. And we're seeing this around the world. Even Chris, we've talked about this multiple times in the UK.

The temperatures are changing where you don't have, you don't really have conditioned air in your, a lot of the markets there where here we have conditioned air because of winters and stuff, but we're seeing that more and more, you might've designed a system 20 years ago, but now the conditions for that same system are different.

The temperatures are changing where you don't have, you don't really have conditioned air in your, a lot of the markets there where here we have conditioned air because of winters and stuff, but we're seeing that more and more, you might've designed a system 20 years ago, but now the conditions for that same system are different. Chris: Right. Not necessarily pipe sizing related, but I had one where there's a brand new fish counter in a, in an open market, effectively inside a building. Peak summer, so you're talking probably in that place it was 35 celsius plus it was

hot. Especially, you know, I don't like the heat. I was sweating in there going in to fix it. Brand new piece of equipment, someone had installed it. It was an imported piece of equipment so I had to ring the manufacturer. They basically checked, you know, that plate evaporator should be suitable for this temperature in this product.

But where the condensing unit underneath hadn't been installed. As per the original design, it was actually only probably another 20 feet away, but that additional suction soupy is picking up between that point and there, was just pushing it outside its operating envelope. The discharge temperatures are at, you know, Didn't quite get burned off of it, brushing my hand a bit, but it was getting to that point, you know, you're talking 100 Celsius plus easily you know, on a 404A system.

It was, yeah, that was sort of my first introduction to, you know, the difficulties with where pipework goes to. And how it can actually impact the operation of the system more so than just, Oh, it's you know, that one's cheaper or whatever and, You know, I never understood why we sized the pipework like that.

It was, yeah, that was sort of my first introduction to, you know, the difficulties with where pipework goes to. And how it can actually impact the operation of the system more so than just, Oh, it's you know, that one's cheaper or whatever and, You know, I never understood why we sized the pipework like that.

And after that, it actually probably sparked my interest in that, And then it got me into the rest of the design field. But it only takes one job like that, which is a bit out of the ordinary, As a solution, to get into a bit more, I wouldn't say an engineering mindset, because we all have that. But in terms of, Is it something which isn't just easily replaceable?

It's not something that's failed on the system, but has never worked right on the system or has worked right, but now we're in certain conditions where the only thing to do is change the system. It's a bizarre. Happens. You don't come across it very often, I must say. Yeah. But it does happen. And, and that's the thing about piping on the roof.

Like I've done so much con, you know, you put a condensing unit up on the roof and you have to pipe to it. That installation, if you're, if you're 150 degrees on, on the roof, you get, take that into consideration. Even though you have installation, you should probably make it thick. Make it thicker. If they say it's a three quarter, maybe you should put an inch and five or whatever on it, because if it gets that hot on the roof and depending on what, what the materials on the roof, it could make it, you know, 20 percent hotter.

Like I've done so much con, you know, you put a condensing unit up on the roof and you have to pipe to it. That installation, if you're, if you're 150 degrees on, on the roof, you get, take that into consideration. Even though you have installation, you should probably make it thick. Make it thicker. If they say it's a three quarter, maybe you should put an inch and five or whatever on it, because if it gets that hot on the roof and depending on what, what the materials on the roof, it could make it, you know, 20 percent hotter.

Up there. Jason has some good points too, about improper slope of suction lines, lack of traps or risers, kind of like we talked about reduced. On traps when they should be especially on low temps, when velocities are lower for sure. Definitely those things you got to look at as well when you're doing your install.

And to Robert's question earlier, talking about inverted traps, there's a few things. I don't know if it's done on CO2, but I know a lot of, especially the manufacturers here in Canada, one of my good friends, Peter, um, from keep right. He sent me some pictures. He'd been doing design for decades. This guy, super smart.

His name is Peter frame and he sent me some pictures of inside these headers. And he, he designs his with something called quills, which is kind of an inverted trap. So yeah, just say you have a six inch header or a four and a half inch header on your rack. The suction pipe actually comes up into the header.

His name is Peter frame and he sent me some pictures of inside these headers. And he, he designs his with something called quills, which is kind of an inverted trap. So yeah, just say you have a six inch header or a four and a half inch header on your rack. The suction pipe actually comes up into the header.

And so it sticks up maybe three inches. And then there's a little hole for oil to get back, but I think that might be, I don't know, Robert, if that's exactly what you're talking about, but that's what I could see as an inverted trap. So any, my, any liquid coming back, doesn't just get jammed right into the compressor.

Right? And the other big thing was in the piping portion, as you talked about insulation and picking up heat I've seen a lot of not, not insulated drop legs from the condenser, whether wherever you're at, whether adiabatic, right? And you're picking up that heat in that drop leg. And 1 of those 1st things, like you said, we have transducers is you're that all that sub cooling that you're getting, depending on where your region is, you know, gets wasted and infiltrated.

Right? And the other big thing was in the piping portion, as you talked about insulation and picking up heat I've seen a lot of not, not insulated drop legs from the condenser, whether wherever you're at, whether adiabatic, right? And you're picking up that heat in that drop leg. And 1 of those 1st things, like you said, we have transducers is you're that all that sub cooling that you're getting, depending on where your region is, you know, gets wasted and infiltrated.

So, those are just 2 key points recently that. I realized that in the old days we had critical charge systems, but just recently I've been in the forefront of the literature of inverting suction piping from liquid migration on transcritical CO2 at the compressor. The one you're referring to is on a suction header, of course. Yep. I've we've seen that before, but specifically that inversion. And then the second is liquid insulating the liquid line or droplet from the condensers. Right.

Because I've even seen discharged lines insulated now on transcritical CO2 systems different lines being insulated to try to keep as much cooling or heating in the, in the system or compressors insulated. Where are you never really seen that on an HFCI system before, but now I'm starting to see different methods of efficiency, but that's a big one.

You said there, Robert was that installation on the drop leg. Cause if you have a, the drop leg and it's 120 out yes. You're still trying to maintain 94. I don't know the behind the scenes for that. Maybe in the winter time. Chris, any, any thoughts on the drop leg being insulated?

The discharge pipe which should be insulated just to, yeah, as a safety precaution in effect. And also a lot of the systems I've done, we've wanted to capture any heat for heat recovery. So it makes sense to keep it in the system and use it elsewhere. I mean, in terms of, Once it exits that, I suppose in periods of subcritical operation, it's then going to go straight through that HPV, drop down again, it would be able to insulate up to that point before it gets insulated, before it goes into our, into our receiver or flash gas vessel.

The discharge pipe which should be insulated just to, yeah, as a safety precaution in effect. And also a lot of the systems I've done, we've wanted to capture any heat for heat recovery. So it makes sense to keep it in the system and use it elsewhere. I mean, in terms of, Once it exits that, I suppose in periods of subcritical operation, it's then going to go straight through that HPV, drop down again, it would be able to insulate up to that point before it gets insulated, before it goes into our, into our receiver or flash gas vessel.

I've never really thought about the thermodynamics behind it, so actually it's more of a, almost an aesthetic consideration, you know, why, why insulate the rest of your system and not one small section of pipework would be my argument. But yeah, it makes sense to in terms of a you know, you want to keep, keep out heat in the system unless it's going out at a heat exchanger. Or I guess cooler in my opinion. I

And I look forward to For the next CO2 experts that you, you come to and share your questions, send some questions in, send your message. If you're listening on to the podcast, get over to the YouTube channel and watch the video. So the slides that you see that Chris went through, because I know sometimes people reach out and it's like, Oh, Trevor, I don't really understand listening.

And I look forward to For the next CO2 experts that you, you come to and share your questions, send some questions in, send your message. If you're listening on to the podcast, get over to the YouTube channel and watch the video. So the slides that you see that Chris went through, because I know sometimes people reach out and it's like, Oh, Trevor, I don't really understand listening.

I need to see, I get to touch. I got to feel I'm the same way. I got to be out there working on the equipment, seeing it, touching it. So if you're listening on the podcast, definitely head over to the YouTube channel and the watch watch the video that. And the slides that Chris just went through, the more you learn, the more you invest in yourself, the better you're going to be and share this knowledge.

One of the things I'm always telling all the people in my community, all the people that I'm training, is you got to share this knowledge. So what we're talking about here today for you to understand it to the best of your ability is actually sharing it with other people, going out and talking about it, sharing that knowledge.

And this is how we get better. This is how we uplift the industry. This is how we all get better at the refrigeration collectively is really sharing our knowledge with others. Yes. There's competition out there. You're, you know, different contractors, different manufacturers, different end users, but at the end of the day, we're all in refrigeration.

And this is how we get better. This is how we uplift the industry. This is how we all get better at the refrigeration collectively is really sharing our knowledge with others. Yes. There's competition out there. You're, you know, different contractors, different manufacturers, different end users, but at the end of the day, we're all in refrigeration.

We want to make it better for all of us, the industry. And this is what, this is what we're doing here. I want to thank you, Chris one more time for, for coming to coming on CO2Xers and I look forward to seeing you all at the next one. Thank you guys so much.