Lesson summary: This transcript covers practical steps for modeling air-cooled VRF systems in eQUEST, including condensing unit setup, system configuration, performance inputs, and modeling considerations. The transcript has been organized with SEO-friendly headings and readable paragraph breaks so it can be posted with the corresponding training video.
Hey everyone, in this tutorial we're going to cover the infamous VRF in eQUEST topic. There is no default VRF system in eQUEST and thus we require a workaround. Knowing that there are several workarounds but of course you have to remember that they're all workarounds and even if you're told what to do, that they are still workarounds and cannot be guaranteed to be accurate. We're going to cover several methods here.
The first method that we're going to cover for air-cooled VRF is probably the method that you're going to choose because we made things quite easy for you. The second method is some method that maybe you'll choose at another time because it can potentially yield and illustrate higher savings but we leave that entirely up to you to decide. I'm just going to show you how we model VRF systems here and you can make your decisions on how you want to model that. First thing we're going to do is we're just going to create a new project from the wizard.
Real simple. Open the DD wizard. I'm going to change this to something like something that's got heating and cooling. Maybe something with a reasonably mild heating and cooling climate like Denver.
The only potentially issue with Denver is that it's so dry but that shouldn't impact our VRF modeling here. I'll leave it as an office building. That's fine. We don't need to worry about the cost that will not impact the system type and we'll continue to the navigator.
Here we just have a shell and we have a system. By default the shell is going to be two stories, five zones a piece, so ten zones. That's good. Let's just set up the system.
The key thing here that we're going to want to keep is the system per zone. One system per zone, cooling is DX, heating is DX, there's several heat pump sources that we can have. We're going to be switching it to a package variable volume, variable temperature system, so we'll just select the PVVT system but that will change it to system per floor. We want it to be system per zone.
We can set up our parameters. I'm just going to leave everything at the default because that really won't impact how to model the system. We go to finish. There's several ways if you search around on how to model VRF, actually it's pretty hard to find even a way just searching around through a search engine.
One of the popular ones is published by Diken and that's the one that initially I started to follow but the methodology is really, really slow. If you go search Diken VRF guide, you can find this modeling guide, it's this PDF here, 22 pages. It comes with a download available, not with the PDF but on their website. They have a BDL library data file and they want you to swap that out with your existing eQUEST data file or your BDL library and really all they're doing is they're installing some customized VRF unloading curves into the default library so that they're available in eQUEST.
Then what you need to do there is if we search through this document, we have to follow through this process and you can see it gets kind of long and this is just what you have to do to swap the files out and we're not even to modeling anything yet and not taking anything away from them. They did certainly a very thorough job of adding this but the method here, for myself, I made it easier. We have to go and then there's for every type of Diken system, there's six unloading curves and we have to select them and bring them through here. We'll see what that looks like in eQUEST in just a moment.
Every time you have to model a particular system, you have to go and select these curves and redo this and redo that. I thought that that was a waste of time so I came up with my own way. If we just go to the component tree, our airside systems, we left plenums in the building. We could have taken the plenums out and they're going to be on condition spaces anyway but you see we have a system, space, system, space.
I didn't even name anything. We just have 10 systems and 10 condition zones with each assigned space. If we wanted to install this, we could go into our system, it's going to detailed mode and we could edit our system from here. You can see we have a PVVT system.
Everything's defaults in here. Heating is a heat pump. The system type is PVVT. That's the typical option for a VRF work around.
Instead of going through there and we could have the BDL library installed and import all of the curves into each model, we'd have to do that each time. Alternatively, I created my own files from those curves. I'll open the window here. I just tabbed over to Notepad++ which is the preferred text editor that I use.
This just has some system input. What's in here are the VRF curves that came from the BDL library. I had to change the formats but it's all the same information. That's just some common eQUEST knowledge that the BDL library has a different format than a .imp file.
I broke them up by VRV type for the Diken system. This is a VRV3. They have a VRV4. They have a couple options, VRV4s with either heat recovery and a variable rate temperature or with a heat pump and there ends up being, I think, five options.
Here are the curves and rather than bringing these in one at a time through the BDL file, if we convert them into IMP format, we can import them all at once. I went a step beyond that and I just set up a default system and have the curves set up already. It saves quite a bit of time to do it this way. What I did here, we have this all set up and I just go to file and I put the file into my eQUEST folder.
File import file. We've discussed this in other videos. I have my VRV import files here. Here I just import the system.
We're going to pre-process it. That's just checking for some errors. In order to make this move smoothly, I did have to put in a dummy space and a dummy zone. We could go ahead and delete that.
Here I have this system and let's just look at, or in detailed mode, let's just look at the spreadsheet mode. I have VRV3. Scroll through here. Everything is basically the same.
I put the sizing ratio at 1. I could edit the input file and have it at 1.15 and it would import with a 1.15. If we just look at, let's see, the cooling unitary power. There's a few defaults that I did put in.
Let's look at our capacity curves here. If you see the capacity curve brought in the Diken curve and each system type has a different capacity curve by Diken. Each one of the several system types does have a different capacity. If we look at the heating coil capacity, everything is the same there.
The heating capacity curves, though, we'll see that there is a VRV curve for that. That's just two of the six curves so far. If we go to cooling and unitary power, you can see for the VRV system there's an additional two types in cooling and that would be the same in heating so we have six curves. The curves are multivariate so there's a lot of data points in the curves.
If we just open up this system, there's only a few factors that are significant here. One of them is the fan. I brought in a default fan. The static, if the fan was ducted, the static would be something about 0.5.
For this, because we have one system per zone, when in reality you might have your zones larger and we could have several VRF units being estimated here, you'd want to determine the weighted average KW per CFM and put that in here. These are the main inputs that you would get from your product spec sheet. This would be different from project to project. The other main factor that's going to change is the cooling unitary power input and the heating unitary power input.
That's the EER or COP. For this one, we have an EER, excuse me, a COP of approximately four and that's just the inverse because it's BTUs per BTUs, the EIR. That would be again be a weighted average if you put that in. These values are available from Diken, usually on the cut sheet and you could take a weighted average.
In that case, instead of by CFM, it would be by ton. By cooling ton, you'd take the weighted average or by cooling BTU. A larger unit would have more weights on the total efficiency. Alternatively, if there was a sequencing issue, you could figure out a new weighted COP from that as well.
Keep in mind that units that you're going to install on a project aren't going to typically vary by that much. You should probably be able to come up with a number for this that's pretty accurate. From here, you can see mostly everything else that I have is in green and that means that it was just defaults. The fans are pretty important.
If you note for the fans by default, these are variable speed. If you watched our water cooled VRF tutorial, we mentioned that the fan control has to be constant volume in that case. In the air cooled scenario, they can be variable speed fans and of course that's the major benefit here. Really just a matter of importing the system, setting up the fan power for the supply fan and whether or not there's static pressure if it's a ductless unit or a ducted unit is of course an issue and then the design, KW per CFM.
These other numbers are an issue as well, but we left the defaults. Just the fans and then you want the cooling, unitary power and the heating, unitary power. You can leave the curves. You could edit them.
In theory, you really ought to, but I know that nobody will. Maybe 1000 people and then of course we do want to decide if the fan is variable speed or constant volume and that's really all there is to setting up the system. Now we have to set up the rest of the backbone of the file and that's where this could get a little tricky. Now that we have all these curves in here, what we could keep doing is we could just edit the .imp file and make 10 systems with all different names, so vrv3a3b3.
Or we could change the name of this system. We could just edit this, change the name, re-import, import file and now if we go to actually the wrong one, if we go to vrv import files in system 3, we'll pre-process it again. Since we changed the name, it didn't pre-process over that and we got an additional system type that is identical to the previous one we did. However, my thoughts on that are what you're probably going to do is you import this and then you'll set that up according to basically the three tabs that we said you ought to change.
And so instead of that, you probably set up this system, create another HVAC system, copy an existing component and then you'd want to give these good names, maybe if it's the zone type 2 or 3 or 4 and we just copy that and if we had set up the parameters, we continue to do that, create another HVAC system. Now you can see this still is cumbersome, now imagine having to select 6 unloading curves each time we did this and also 12 because you'd have to import it into your file first. So let me just copy an existing component and we go through here. So we have 4, we have, we call this 1, 1, 2, 3, 4.
And if you're good with the .imp file, you could figure this out ahead of time and you could just copy and paste the system, change the name and use that dummy zone over and over as the control zone and it would import the file that way. So if you let copy and paste in a .imp file better, that would work, but. VRV 6, VRV 7, I don't want to confuse anyone by just trying to save a few minutes. Now what I don't really like about this method is that these are not actually sharing heat between the systems, there's no communication between these systems at all.
They're just simply relying on the unloading curves to assume a standard sort of efficiencies at certain loads that you sort of naturally get with VRV. So we need one more. So VRV 10, copy an existing component and there we have it. And now we just have to go through this and painfully set these up.
What we could do for the first two, alternatively, we could go into a spreadsheet. Oh, that's going to be four, that'd be four, makes sure I'm keeping the pattern correct. I could accidentally alternate this. That's of the window size.
Oh, and we've also want to remember to delete the dummy zone, but we actually can't do that quite yet. Should be correct for that. Just remember these were in order and my nomenclature was a little skipped up here. So we went one, two, three, four, five, six, seven, eight, nine, 10.
So what we can do here is the first one is yell one self perimeter ground. Second one is yell one East perimeter zone. Third one is yell one North perimeter zone. And the fourth one is the core zone.
So one, two, three, five, all five was the core zone and four was the West zone. That's what I get for naming things poorly. Just my one mistake of hyphenating and then not as I was hurrying, it's costing me more time here. So five was yell one core zone on the ground floor.
So Southeast Northwest core is the pattern. North, East, North, West, another annoying window issue, Northwest core. Now, from here, what I can actually do, I can delete the dummy zone now, probably want to delete the dummy space first. Unfortunately that was the only way that I could get it to import without being really annoying and then making you either giving you an error forcing you to assign something to it.
So let's just delete that space and then airside HVAC and delete the zone. We did everything correct. We shouldn't have a problem deleting the dummy zone. Otherwise, the dummy zone was the control zone for every system.
We should be able to delete these. Actually, I don't really think we have to delete them, but just to clean up the model, it's easy enough. So there's other things we could have done. We could have copied and pasted the unloading curves into these PVVT systems just based on our spreadsheet from the imported systems.
So there's multiple ways that we could have done this. I'll save one of these just to show you what else we could have done rather than creating new systems. So here we have the one blank system left. It's a PVVT.
Everything was basically the same. Now I did change the sizing ratio. It's really no big deal. That's something that we could edit in the .imp file.
So if you recall, we had the cooling coil capacity. Actually everything was the same. The capacity curves, sorry, were different. And so right here, we could just set the VRVAC, and you have to make sure it's the same one.
This gets very confusing very quickly. So we could just set that, and then we scroll over that everything's the same there. And then it would be the heating or the cooling unitary power, 0.2565, we could just go control C, control V, control C, control V, and we could have done that for all the other systems then we would have to do the same for the heating coil capacity, the heating coil capacity curves. So just control C and control V, and alternatively we could have just changed a number of these rather than creating them or deleting them.
So depending on how many systems you have in your file, that would be up to you. So we still need to go to heating unitary power. The efficiency was definitely different, and then we can copy and paste one of these, you'll notice this is the heat PLR. For whatever reason, when I copied and pasted, it pasted the wrong one, and you definitely want to do that.
I tried to copy and paste both of them at the same time thinking it would work, and it did not. So you definitely would want to look through it and see that that was consistent, because that would be a major discrepancy in the two curves. And that would be another way to set up these systems. So we could basically just copy and paste all of the inputs from the imported system, which maybe that would have been faster, it's hard to say.
Definitely would have been faster if there was 20 or 30 systems. I'm going to delete this one anyway. It probably would have been faster, because then we would not have had to change the control zones. But you live and learn, I typically would have done the opposite method, and I would have probably just copied a bunch of systems from the .imp file.
But alternatively, the copy-paste method would probably work pretty well. So you'd have all of these systems set up as VRF. The main problem with the copy-paste method is we are assuming that these are all VRV3 systems right now. If we had a mix of different dyke units, VRV3, VRV4, VRV4, VRT systems, we would have a whole different set of unloading curves, and we'd have to identify each one of these one by one.
We also have to identify the efficiencies for cooling and heating one by one, and so on and so forth. So it wouldn't be that easy. We can easily make some mistakes with any time we change the fan or anything like that from the default systems. The method that I showed is probably going to keep you a little bit more on your toes in terms of accuracy.
And from here, we can simulate, and we have a workaround for a VRF modeled, and that's all there is to that. The next method we're going to show you is actually, in my opinion, it's a better method, but I don't really think many people will use it because it's a lot more difficult, but it should be more accurate. In fact, it's more accurate, and it probably doesn't save as much energy. So all right, looking forward to that, hope you enjoyed this tutorial.
You can find these unloading curves when you sign up for the course. They should be available on the course page. Alternatively, they may be in your downloads folder at your user account. Okay, good luck with the modeling of VRV systems.
This lesson provides a practical reference for modeling air-cooled VRF systems in eQUEST. Use the organized transcript alongside the video when reviewing the VRF setup, condensing unit inputs, piping assumptions, and performance settings.