28 - VRF systems

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Let's talk about the VRF system, here. I actually saved a new version of my previous model. I removed all the zone equipment, as you can see in this thermal zone tab. This air loop, which is connected to dedicated outdoor air system, and these are single duct uncontrolled diffusers for the ventilation requirement air loop. There is nothing for primary and primary heating and cooling. I can also show you how my air loops look like, for now. Here we have this, service hot water, which we are keeping it from last session, last week's session. There are two air loops for ventilation requirement. Both of these loops, they have single speed DX cooling coil, as well as one a gas heating coil, which is connected to burner, furnace, okay. Now we need to bring VRF systems for primary heating and cooling.

Basically VRF, or variable refrigerant flow system, is a kind of heat pump that uses refrigerant as the cooling and heating medium. The refrigerant is conditioned by an outdoor condensing unit. And, it can be circulated within the building to multiple indoor units, okay. Again, this is a kind of heat pump, as I mentioned, it works on different principle. It needs to have lot of performance curves, I’ll show you how it works. But, a good thing in OpenStudio is, you can actually download the indoor, as well as, outdoor VRF units from the BCL library.

You need not to worry about putting all those values for like, 15 plus curves. I don't even remember how many these are, but I'll show you how they look like. For VRF, what you need to do is, you need to go to this separate screen. OpenStudio has its own interface for VRF, click on this here. And it will take you to this empty screen. It says just, drop VRF system, okay. First of all what you need to do is, you need to bring a VRF system. Before I move to the next step and explain to you how to use, or how to install a VRF system in OpenStudio models, let me explain a couple of things here. You can actually install multiple VRF systems in a single OpenStudio model. But, in EnergyPlus, it's mapped as one is to one object. It means that you need to provide a VRF terminal for each and every space. You can't just provide two spaces, or two thermal zones connected to a single VRF terminal, okay. You can import the equipment data directly from BCL library. And then, once you have those systems, indoor and outdoor unit systems in your model, you can edit them. you can configure them, you can do lot of things with them, okay. Let's go to library, now. Here, and if you scroll down to V, that's where you'll see the VRF terminal. Basically, these are indoor units, and this VR system, the outdoor unit, okay. As you can see there are some, there are some equipment’s already in my library. But, if I go to components and measures, try to find components, and go to HVAC, you will see a lot of options for VRF systems.

For example, if I look for something like LG, let’s see, let’s search for LG. LG has its own units. You can see here, look, variable refrigerant, all of them. All you just need to understand is, there difference between the outdoor unit as well as indoor unit. You can see this terminal unit, which means it's an indoor unit. If you go, if you look around, you’ll find a lot of outdoor units, as well. Let's just search for outdoor, if you find something. Well actually, yes, you can see these other outdoor units, now. What I'm going to do is, I'm going to bring one of the existing library materials to my model, BCL library, okay. Building component library. We have a lot of options. Please, go through all of them. For example, LG electronics, this is the model number, you can actually google this model number, you will find lots more information. But, as you can see here, all the information is already provided. This is the outdoor unit, here. The tag is given, here. All the information is there, capacity is there, heating and cooling capacity performance, coefficient of performance is there for heating and cooling. You have a lot more information. They also come with their own curves. For example, if I download this particular outdoor unit, the name is ARUN121DTE4, download. And then I shall look for some indoor unit. For example, this one. This is also a window unit it seems. The terminal unit, you can see. Click on it. You will see here, on the open setting bottom, the tag is window unit. Download this one, as well. I think that's it for now. We can like, install multiple outdoor units, install multiple indoor units, you can do a lot of things.
Once we have these things closed this screen. Then drop this one of the VCL component, the VCL system that we installed or downloaded in our materials in our library just now. Again, go to VRF system, look for VR system in the library, as well. Try to find the one which we downloaded, just now. I think this one. ARUN121DTE4. Drag and drop it, here.

Now we have this, LG Electronics USA outdoor unit. If you click on this tiny plus sign, we take you inside the system. And now, it asks you to drop the VRF terminal, okay. Again guys, very important. We already have a dedicated outdoor air system to take care of ventilation requirement. We are working on the primary heating and cooling source now, okay. Now we need a VRF terminal. We can install the one which we download just now. I think it was this ARNU423BGE4. Drag it and drop it in this VRF terminal box, here. And now, the next thing that you need to do is, you need to drop a thermal zone in this, okay. Go to my model, and in terminal zones, drop one of the existing thermal zone, here. The first one is closed office 2. That's it for now. Let's work on some details first, okay. If you click on this outdoor unit here, it takes some time because as I mentioned there are so many curves that are associated to one VRF unit, outdoor or indoor unit. It takes a lot of, it needs to sync a lot of information and background. And, because of that sometimes it doesn't respond immediately. It takes some time, maybe like 30 seconds or something.

We need to be patient with OpenStudio interface here, okay. I think it should be done in the next 15 to 20 seconds, all right. On this right-hand side you can see, you can edit the properties of this outdoor unit. You can change the schedule. The total cooling capacity is already given, as for the manufacturer data, COP is given. You can see there’s so many curves here. Like, low temperature curve, cooling capacity, cooling capacity ratio boundary curve, so many of them. The heating capacity is given. Then all the heating curves, okay. And then, you have the zone name for master thermostat location. You can actually install the thermostat location within this outdoor unit. The master thermostat priority control type is there. The default one is, load priority. Thermostat priority schedule, do we want to recover the waste heat from this heat pump. And this is a very good feature, if you cook for yes, then you will find some savings at the heating side. Then your equivalent piping length use for piping connection, the default is given. You can change it based on your design. Then your vertical height given. What else do you have, you have equivalent pipeline in heating mode now. Then you have crank heater power for compressor, the default one is given. You can change it based on your own design, with the information what manufacturer have provided for this particular system. And then you have defrost control, the same information that you need to provide for other heat pumps for some of the HVAC systems. And, if you keep scrolling down you will find a lot of other information, the curves and all. If you download this information from the BCL library, you do not worry about changing all these outputs, or inputs, sorry.

As you can see there's so many of them. If you keep scrolling down, there at least like, a thousand plus inputs. That's why their BCL library is very handy. You can download this information, which can save a huge amount of your time, all right. Now click on this indoor unit, over here, the VRF terminal. It will also have multiple curves. It will also have a lot of information that you can edit. But again, as I mentioned, we have downloaded this VRF terminal system from BCL library. Chances are that you need not to worry about the inputs that much, okay. You can see on the right-hand side, we have this terminal box. Now, it has it’s supply air flow rate. It has supply for cooling, as well as for heating. A lot of information is auto sized. Then you have this parasitic, left-click, energy usage. And, what else. You have this on/off fan. You can actually change this fan in the OSM file, if you just open it in Notepad++. We don't teach that in this introduction class, but if you need any help, please let us know. What else? The curves are there. There are, again, a lot of curves, as I mentioned earlier. The DX cooling coil is there, it has its own capacity. Rated sensible heat ratio, the rated airflow. Then, what else do we have. It should be a heating, cooling, coil, if I’m not wrong. Let me just scroll down. As I mentioned, there's so many, so much information that you can provide to this VRF terminal thermal zone system. Then, you know, this heating DX coil, the capacities are given and then I get a lot of curves, okay.

Once you are done with editing these systems, either you can just go here in my model and drop another thermal zone in this drop thermal zone section, and it will bring the exact VRF terminal for you, okay. There's another method, or, I think, let me just say, I don't remember now. I think you can also just like, click on this. I am sorry. First check all those thermal zones, the same process that we did for fan cooling systems, as well as for water sourced heat pumps. Again, as I clicked on them, it’s going to sync all the information for VRF system. It may take some time. For example, if I just check these options here, again, all those thermal zones. And, if I click on one of the existing VRF terminals, I can just copy paste the exact same information. Same way that we did for fan cooling system, as well as for the water sourced heat pump. Click on this, apply to selected, and you can see all the information is there.

If you go back to the HVAC system stats, and go to VRF terminals, VR system, well, this very interesting. You can see, we actually copied the information there but you don't see it here. That's very good to know. It looks like the systems that we duplicated there in thermal zones, they are not visible here in this VRF interface. I don't think it's a very good strategy. I think it's some limitation. The system is there. You need to either, work with this, the system is already duplicated, I think this is an error. I think it's my mistake. I'm just going to delete all of them. That's good to know that you can't do this, okay. I always use the easiest method, which is just, copy paste the thermal zones within the VRF interface. This is the first time that I've tried, even here. I don't think it will work. We can just run this simulation for you. You know what, let's just run it, okay. It's good to know, for all of us.

All right. The simulation, it was working fine initially, but it crashed on me. I go to, show simulations. And, if I open this eplusout.err file in Notepad++, now it will show me the severe, or fatal warnings, you can see. The zone HVAC terminal box is not connected to condenser, which makes total sense right. We actually copied the VRF units, here, VRF terminal boxes, here in thermal zones. But, they were not able to get attached to the VRF condenser unit, condensing unit. Let's click on one of the VRF refrigeration terminal box or terminal unit. And, can we connect them here. Let's check. Well, there is a lot of information here. You can actually create a lot of reports. And, just check this option, and they will create the reports for you. But, for now, let's go to the next tab, the HVAC systems tab.

And see what can we do here. The easiest way is just go to my model and bring all that information one by one. I think that's the easiest process. What I'm going to do is, I'm going to go back to my thermal zone tab. Go to these zone equipments, the VR systems, and delete them one by one. Again, this process will take some time. What you can do, you can just like, delete them on my one. Like, you know, by clicking on this cross mark. And then, go back to your HVAC system tab, go to your VRF interface, and just install all those VRF terminal units one by one. You just need to drag thermal zones from your my model to your VRF system, here.

You just drop into this VRF terminal, I'm sorry, drop thermal zone section. I’ll just show you how can you do it. Like, you know, just drag and drop as I mentioned. And, you will keep seeing these new VRF terminal boxes. This is one of the process, and I can show you another process, one more process. I'm just going to delete this one for now. Let's say if I delete this VRF system, delete all those air loops. Go to components and measures and apply measure now. I'm going to find one of my customized measures, which can create the UES system, as well as, the other system for me. And, when you get familiar with those OpenStudio measures, chances are you won't even create those complicated systems manually. Like, as you can see, even I got confused initially that, A, can I install those VRF indoor units within the thermal zone tab. I wasn’t able to do it. I assumed that I can do it but it didn't work, okay. Make sure that you know the process first, and then jump on these measures.

For example, if I go to this VRF measure, apply it. This measure won't be available on PCL library if I’m not wrong. This was one of our own customized measure. You can see the building started with zero plant loop, zero air loop and one plant loop. It has the same final condition. But, let's say Y didn't pick up any VRF systems. Let’s say, accept changes. And if I go to my VRF feed, do I see something there. That's a bit weird. Let me just apply the measure again, one more time. And, let's see if I need to do some changes in thermal zones. Well, I know what's the reason, because we have these zone equipment floating. Let me just install the ideal air load. As I mentioned earlier, you should clean or you should purge your energy model as much as you can. You don't want to have some unnecessary information floating in your energy model. It can definitely cause some errors. If you go back, components and measures now, apply measure now, save the model. And, if I go to HVAC systems, whole system, and look for that measure, particular measure, VRFwithDOAS, and apply this measure now. Well, my model crashed on me unfortunately. I need to open it again.

Again, sometimes when you work on these complicated systems and you screw things up, you can have these crashes which is like, you know, very unfortunate. But again, this is very good to understand. Now you know what you need not to do. If I go back to my thermal zone tab, and you can see, I already have those ideal loads installed. What I'm going to do is, I'm going to look for that measure again. Again, you might not find this measure on your screen. This is only for demo purpose. If I go to VRF system, apply this measure. Looks like my model is not working fine somehow. Let me just go back to, one more, let me just go back to my model again. And, in file, I'm going to open this. Let me just open one of the recent files on which I did some experiments. Maybe I like, did some changes and did some serious mistakes. It can be possible, right. Like, I'm doing so much stuff on one same, or like, one file. Maybe something happened wrong in Bangkok. Let me just install the ideal air load in this existing airstream model. At least the demo should work. Go to measures, apply measure now, save it. And, it’s good that the model is crashing in a live class because, that way you understand what you need not to do. As you can see, measure, VRF dedicated outdoor air system. Look for some options here. Check some of the components and measures, and hit apply now, okay.

It has a lot of arguments that you can change, a lot of inputs that you can change on screen number one. And now, error, looks like it actually crashed on me, again. I have no idea why it's not working, which is kind of weird, okay. Let me just go back again and see if I can do something else, all right. It happens, it's all right. Apply measure now. All right. It worked, this time it seems. I'm going to accept changes. And, now you can see I have this dedicated outdoor air system. I don't know why it like, this first thermal zone, maybe I unchecked some options in the argument section of OpenStudio measure. And, I have this refrigerant flow systems available, refrigerant flow system. If I go to my HVAC system tab, and go to VRF systems, you can see I have two VRF outdoor units. And, the second building story, second is connected to eleven terminals. And, building story one is connected to six terminals. You can see all those thermal zones load, okay. And if you go to dedicated outdoor systems, you have those air loops. They have connected to single speed DX coil as well as furnace and refrigeration requirement, okay. That's how the VRF system works. I hope you liked this session. Please practice and let us know if you have any questions, okay. Thank you. Thanks so much guys. Take care. Bye.