26 - FCU with DOAS systems

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´╗┐Hello everyone. This is Harshul Singhal, again. In our last class we worked on a VAV system with reheat coils. I explained to you different kind of loops that we can create for an HVAC system in OpenStudio. We created air loops, we created different kinds of water loops. For this class we'll work on some complicated systems. The first one that we're going to work is a fan coil unit system with dedicated outdoor air system. If you're familiar with fan coil with dedicated outdoor system, basically you need a separate air loop for ventilation requirement. And, the primary heating and cooling is taken care by fan coil unit systems, okay. These fan coil unit systems in OpenStudio needs to be zone equipment. And, they can either have their own heating and cooling coils, or you can just connect them with your water loops, the water use that you need for your ventilation requirement loop, as well. There are different options. I would like to explain to you how the water loops work with this kind of system. How can you bring the water, water coils for zone equipment, as well as for your ventilation requirement air loop, okay.Let's start on OpenStudio now. Let me just go back to my OpenStudio model. Here I have already saved a new version of my OpenStudio model.

I have renamed it on today's date with proper nomenclature it says the DOASFCU. DOAS means dedicated outdoor system and FCU is fan coil unit, okay. For this class I'll explain to you two ways to create this kind of system.I'll I will start with this manual method, which will take more time than usual. Like,we'll create each and every component that is required for this HVAC system. And, once we are done I'll show you the shortcut method, which is the use of OpenStudio measure. OpenStudio measure can reduce your workload to a significant amount. We can literally create this complicated system within 30 seconds, okay. Let's start with this thing, this fan coil unit system. First let me just show you what do we have in my OpenStudio model so far. I cleaned my previous model, my last model. I have just this hot water loop that we created in our last class.I'm going to start everything from scratch. I will create air loop for ventilation requirement. I will create water loops, one for hot water, one for chilled water. And, if required, we'll just create a condensing loop, as well. Or, we can just skip it to save on time, okay. And,we'll also create some zone equipment. We need to have some four pipe fan coil unit systems, four zones. And then, we connect those FCU boxes to your water loops, all right. Let's go to this top left part and click on this plus sign. Scroll down and click on this empty air loop, add to model. And, first and foremost thing is you need to rename it, okay. Let's rename it to something like, ventilation, or maybe like, DOAS air loop. Again, very important thing.

I don't like to keep any space between the names, here. Like, you know, for example, if you name like this DOAS space air space loop, then when you run the simulation, you might get some trouble during simulation. I would always like to provide either a dash or like, you know, underscore, or maybe nothing, like, you can just rename it something like this, the way I have done on my screen. DOAS-airloop, that can also work. And, the next thing is you want to look at all these inputs that you need to provide. I can just keep auto sizefor now. The rest of the information can be default. The next thing that I want to do is size my system. The default for this size on is sensible, you want to change it to ventilation requirement. And then, either you can auto size it or hard size it. Again,it's totally up to you. For this class I will keep auto size. Minimum system airflow ratio should be 100 percent for a dedicated outdoor air system. Change this number to 1. Preheat design temperature, preheat design humidity, looks fine to me, I won't change these numbers. But, you can change this central cooling design supply air temperature and central heating design supply temperature, okay. It's really up to you like, what values you want. Like, for example, a lot of times people say, people think that heating design temperature can be somewhere on 75 for a dedicated outdoor system, which seems reasonable to me. And, central cooling design supply air temperature can also be somewhere around 70-75. Let's change these values.

You don't want to give these values extreme, something like, 5four degree Fahrenheit for cooling. It's not a primary heating or cooling system, okay. Please remember this. What else can we do here. We can change, we need not to change this input, here, hundred percent outdoor air in cooling and heating. It should be same, what you have on your screen, okay. And, what else. I think the rest of the information is fine, for now. The next thing that I want to do is, bring a fan, okay. Let's bring a fan, here.Scroll down to be this library option. Look for available fan or constant volume fan, it's stored here per your design.I'll bring constant volume fan for this. Let's say we have a constant ventilation air loop working in this building, which is like, 2four hours running, okay. You can rename it if you want. I will just rename it to something like, DOAS fan efficiency. You can change it to something like, efficient fan.85% pressurized, I would keep like, one for now. Again, you need to use some fan calculator, as per ASHRAE 90.1 appendix G, okay. Maximum flow rate can be auto size.Motor efficiency 90% looks higher to me, on the higher side to me. I will change it to 80%. The next thing that you want to bring is outside air controller. Same process, what we did for a primary air loop, okay. You can rename it if you want. Something like, DOAS underscore OA system. You can just keep these values auto sized.

Do you want a economize the control type, yes,let's change to fix dry bulb temperature. And, you can change this economizer travel temperature value too, lets say, 75, okay.
Again, I'm using all ASHRAE values. Let's say, this value is 75 as per ASHRAE 90.1 appendix G. What else can we change, here. We can scroll down, you have a lot of other values to provide in case you want to. You can provide some schedule for minimum outdoor air or maximum fraction of outdoor air. Again, it's totally up to your design, okay.I'm trying to keep as simple as possible for this class. The next thing you can provide is,let's say we have a heat exchanger for this outdoor air system, outdoor air controller. Let's go, scroll down and find this heat exchanger, I think it should be from H if I'm not wrong. Yes.It's heat exchanger air to air sensible and latent. I'm going to bring this, drop it here. Drop it over one of this node, here. And, you can rename it if you want. This name seems fine to me. You can hard size it, you can change these effectiveness ratio for sensible and latent airflow. I am going to keep the default values. And then, you can change the heat exchanger type, rotary or plate,whichever is like, feasible for your design. Do you want a frost controller type, if yes, change it. Otherwise keep no, that the default value. And, do you want the economizer lockout, if yes then the default works for you. If not, you can change it to no. Let's change it to no, for now. And, the next thing that you want to bring in this air loop is a coil, heating and cooling coil. Scroll up, go to C, everything is alphabetical, as I mentioned earlier. Bring this CHW cooling coil and then scroll down to heating coil. Bring this HW heating coil. We have both these coils. We are going to connect these coils to their associated water loops later. Let's just finish this air loop for now. The next thing that I want to bring is a set point manager. Remember, like,set point manager is very important for these air loops, as well as for water loops. For now, I am going to bring the easiest one, the scheduled deck temperature.

And, remember, this deck temperature default value is 55 degrees Fahrenheit. I want to change it to 75 degrees Fahrenheitbecause, it's my ventilation requirement loop, okay. This is the name, deck temperature. I'm going to click on this schedule tab. Go to schedules, look for deck temperature,this is the one.I'm going to rename it to something like, deck temperature DOAS, and change this value to, let's say, 75, okay. And, if you are confused about this schedule manager, the set point manager, look for my previous video that I created for you guys last week and you will understand the purpose of this set point manager, okay. It's very important to provide a set point manager in an EnergyPlus model or OpenStudio model, okay. Click on this air loop again, the HVAC systems air loop. You can see here on my screen this one, click on it.
And then, we can bring more changes. The next thing that you want to bring is some kind of components for a demand-side. I think we are done with this supply side. Now let's work on this demand side. The first thing that we need to bring is a simple diffuser. We don't want a fancy diffuser like, reheat, or BUI, or something like that. We can just bring a simple diffuser which can be, let's say, you can see there are like, so many options even for air loop,HVAC, diffusers, dual ductVAV is there. I'm just trying to find the easiest one possible for us for this kind of ventilation requirement air loop.

Let's see, give me some time, okay. I think, no, I don't think this will work. I know that it's like, such a long list. Sometimes even I get confused here when I'm looking around for things. The one which we need is a single duct VAV with no reheat. I think this one,okay yeah, this one. This is simplest diffuser possible. You can see there is no connection for any air water loop, or any coil. Like, just a simple diffuser, okay. Now we have a diffuser. It has constant flow it seems, the minimum flow, air flow fraction is 0.3.I'm going to keep the default values now.

But, you can change them. If you want to control for outdoor air, if yes, change it. You can provide the schedule, as well. It's totally up to you.I'm going to make my things easier here, for this class. Click on this splitter, and you can bring all the thermal zones that you want to attach to this air loop. For simplicity,I'm going to attach all my air loops. And, you can see,OpenStudio creates the rest of diffusers automatically for you, okay. Remember the process you first bring in a diffuser, connected with one thermal zone. And then, just click on this splitter and bring all the rest of information that I am trying to do here, okay. As you can see, I am bringing all the thermal zones to this air loop for ventilation requirement. Again, in most of designs, you might have separate dedicated outdoor air system loops for different floors, okay. First floor has its own dedicated outdoor air system, then second floor has its own dedicated outdoor air system. Again, for simplicity,I'm just going to connect all my thermal zones to this one air loop, the ventilation requirement air loop, okay. Now I am done with my dedicated outdoor air system air loop. Next thing that I'm going to do is create a chill water loop, okay. Again, click on this plus sign. Just go and scroll down to empty plant loop, click add to model. Click on this dotted line. Rename it to,let's say, chilled water loop. Filtered water is fine. Maximum loop temperature can be,let's say, I mean, it won't matter here because this is the maximum value for a chilled water loop. I know my maximum value will be somewhere on 56, looks reasonable. Minimum loop temperature can be fourfour. Rest of the information can be default, for now.You can provide some sizing.

You have to because the default value is heating for loop type, change it to cooling. And, design loop exit temperature can be somewhere around fourfour. And, the loop design temperature difference can be 12 degree, okay. I'm using some default ASHRAE 90.1 values, okay. And then, we can bring some supply-side equipment. The first one that you want to bring is a pump. Scroll down to P. Again, everything is alphabetical.I'm going to bring a variable speed pump, you can rename it if you want. Let's just do it real quick. Cooling loop pump. You can hard size it if you want. You can change the pump pad based or your own calculation as per ASHRAE 90.1 Appendix G. You can change the rated water consumption to hard size value. Rest of information looks fine to me, I'm not going to change the performance curve, as well. You know the drill, right. I explainedto you in my last session that you can change these values as per PNNL reference guide. And, we can move to the next thing, which is like bringing a chiller, okay. You can also bring bypass pipes. Again, you can bring multiple chillers, but for now let's just bring one chiller, for now. It can be electric air cool chiller. You already know how to create a water cooler. I'm just going to show you how to create an air loop chiller. If you have an air loop chiller, air cool chiller, sorry, in your OpenStudio model, you need not to create a condenser loop again, okay. Very simple. You can change the reference COP values, you can change the reference leaving chill water temperature.

There are some default performance curves. You can either keep them for your model or you can change them based on your manufacture data. Or, you can always refer the ASHRAE PNNL, I'm sorry, to the PNL reference guide that I explained you in my last class, okay. Next thing that I'm going to do is, I'm going to bring a schedule manager, again. Let's bring something like, the easiest one again, the scheduled one. Bring this schedule CHW temperature, click on it. And, the schedule name is chill water temperature. Go to schedule tab and check what is the value that you have for this chill water temperature schedule. Looks fourfour, fine to me, okay. I already QCedit, it means the default value for this schedule manager is fine. I can go back to my plant loop. This is my plant loop, here. The next thing that I can bring is something on demand-side.

What I can do, I can just go to my model, go to cooling coil water, and this drag and drop this existing cooling coil that I have created in my air loop. This cooling coil is connected to my dedicated outdoor air system air loop, okay. There is a shortcut now, you can see there's a shortcut that opens to, OpenStudio creates for you automatically. If you click on this tiny link thing, it will bring you to the chilled water loop, okay. The next thing that I want to do is, create a heating loop. I think we are done with this, it's the easiest chilled water loop.Click on plus sign now. And, scroll down to empty plant loop.

Again, same drill. Rename it to something like,HWloop. Filtered type water is fine maximum. Group temperature can be 180 degrees Fahrenheit. Minimum can be,let's say, 120 or 150, or whichever value is convenient for your energy model. Go down to sizing. Design loop exit temperature, 180 seems reasonable to me. Loop design temperature difference, 20 seems reasonable to me, again. Once I'm done with this sizing, I can go to library. Bring the pump thing, first. Scroll down,rename it if you want. It makes your life easier later when you try to QC your results. I always like to rename them. I know it's additional time, but again it saves a lot of your energy when you're trying to QC your results, okay. You can change pump head rated flow rate, your efficiency. Once you are done with this you can go back to library, and scroll up to boiler option, okay. Boilers are, here. Just drag and drop here. Again, same thing, you can rename it if you want. You can change the capacity, efficiency, or the, this efficiency curve. Again, you should look into the curve for boiler. The default one is constant value which actually is not right. You can always create your own library. If you want, I can show you to advance user, if your request me through email. But, for now, you can just change these values manually.

Like, for example, if this value is,let's say, 0.85, and your coefficient is, let's say, 0.15, okay. The curve is 0.85 plus,I'm sorry, 0.85 is constant. Plus 0.15 into 2x.This is driving factor of your efficiency, boiler efficiency, okay. This is the easiest curve change that I've shown you. Like, definitely you'll have some coefficient 3, as well, for your boiler. If you have a complicated boiler then you might have more options here. You might have more coefficients.
Let's go back to library and bring a schedule manager. Scroll down to,let's say, schedule manager. I'm going to bring an outside air reset schedule this time. Or, you can bring to us like, you know, any other reset. It's totally up to you. Click on this, and you can change these values.
Let's say,set point at outdoor low temperature is 180. Outdoor low temperature, let's say, is 20 degrees Fahrenheit. Set point at outdoor high temperature, let's say is, 150. And, outdoor high temperature is, let's say, 50, okay. Looks reasonable to me. And, if you are happy with these values you can move to the next step, which is bringing your a hot coil, hot water coil, and drop it here at demand site, okay. Again, it created this linkage for you. Click on it, and it will bring you to the air loop. All right. Looks like we are done with this air loop and plant loop thing.

Now, the next thing that we need to do is, create zone equipment. This, whatever we have done so far is for ventilation requirement. Now, the next thing is to create primary heating and cooling systems, which is FCU, fan coil unit system for our project, okay. Click on this thermal zone option here, the zone option. And now, you can see in air loops, you have those dedicated outdoor air system air loops. And then, you have these diffusers. You can always rename them if you want to make your life easier doing QC, okay. For now,I'm just going to keep them like, as it is. The next thing that I'm going to bring is, I'm going to bring some four pipe fan coil unit systems from library. You just click on the library, and look for a fan coil unit systems. Here it is,four pipe fan coil unit system, there are different options here. There are some constant a few flow fans, fan coil unit system. And, there are some variable fan coil unit system. For this I'm going to bring this variable fan coil unit system. Just drag it and drop it at one zone side, at one thermal zone. Again, if you remember from my previous class, you always drop your zone equipment in this column, this zone equipment column, okay. Drag it and drop it here, okay. You can rename it if you want. I like to rename them, but for now,I'm just going to use my easiest option, just FCU-1. You can change the schedule if you want to turn off these systems at some specific hours, you can totally do that by creating this schedule. You know, the, how that on/off schedule work. We already have worked on that kind of schedule in my previous class. You can change the supply air flow, you can change the capacity control method. If it's a cycle cycling fan you can just look for this option. Do you want an ASHRAE 90.1 variable fan, go for it, totally up to you.

I'm going to keep this default option, for now.Now, the next thing that you can change is sizing, I'm sorry, the supply or the air ratio. You can change the maximum outdoor air flow rate. Since we have the dedicated outdoor air system, this option will be zero. Remember, we are not bringing any outdoor air flow rate through these zone equipment. They are the primary heating and cooling system only in spaces, they are not connected to any outdoor air controller. Do not bring any outdoor air in our spaces. All the ventilation requirement is being taken care by our dedicated outdoor system air loop, all right. In case this value is zero, you need not to worry about any schedule related to the outdoor air. The next thing that you can do is, scroll down and look for other options.I'm just going through the most important one that you need in your energy model here, for this particular system.The next thing is fan. You can change this fan value, fan option. Let's say, I can rename it to something like, fan1 underscore FCU, something like that. You can change the schedule, as well. Efficiencies,let's say, this efficiency is 0.85 ECM fans. You can change the pressurize. Again, very important, this pressurized looks very high to me for my project. I have to make a calculation for my energy model,it's very important. But for now, I'm just going to give a very small value, like, which I think is like, it's suitable for this kind of system, for this kind of zone fan. You can change the the efficiencies here for for your fan by changing the coefficients.

And, the next thing that you want to change is a something related to the cooling coils, cooling and heating coils. You can rename them properly . It looks like it's a very long name.I'm just going to rename it to something like, FC1 underscore cooling coil. You can change the schedule when you want to make it available. You can change,you can hard size them if you want. You can change the analyst type, the heat exchanger configuration. Cross flow seems fine to me. Same thing with your heating coil, rename it to something convenient, heating coil FCU-1, looks fine to me. Same thing, you can change the values there. Like, maximum water flow rate, okay. The next very important thing you need to do is, you need to connect these fan coil unit systems to your water loops. Click on these linkages here, you can see here. Click on the first one. It says, connect your heating water coil to your hot water loop. This is what we created recently. Click on this. Same thing with the cooling water coil, connect it to chilled water loop, okay.
Looks like we are done with this FCU-1 system. There are a couple of things here. Either you can just copy the exact same zone equipment to each and every thermal zone, or you can create everything from scratch, again. Like, it will take more time.For this class I'm just going to copy the exact same system for each and every thermal zone. My values are auto sized so this auto sized FCU-1 will work for rest of them. What I'm going to do is, I'm going to click on these options here, the second row here,I'm sorry, column here, okay. It will allow me to copy the FCU-1 system to each and every thermal zone. And then, select this FCU-1. When you click on it, you can see this, apply to selected, option here, on top of this column is activated now, okay. It's live now. If you click on this, apply to selected, it will copy this FCU-1 to each and every thermal zone that is, that I have selected here in second column, okay. It's going to take some time. And now you can see the nomenclature isn't very great, but you can change it. Looks like if I click on this it has exact same values, which I created, or provided for FCU-1. I still want to check whether these new FCUsare connected to those water coils. Looks like they are, okay.

Again, if you go to the air loops, or water loops here, just want to confirm if those water coils are visible in the water loops. Looks like all of them are visible here. You can see these free-floating water coils here. They are connected to those FCUs.

Let's check with hot water loop. Yes, you can see those free-floating hot water coils from FCU systems. And, there is one heating coil from your air loop. Looks like I'm good to run this simulation.I'm going to click on this sign, and click on the run, okay. It will take 15 to 30 seconds to finish this simulation, and let's see if we find any error to QC. If not,we'll move to the next step, which is a demonstration of creating a similar kind of system using the OpenStudio measures, which is super convenient. Took me almost 15 to 20 minutes to create this system, or maybe more. And, I created very simple system here, mind you. How can you reduce this workload off like,let's say, 1 hour to 30 seconds or 1 minute. It's such a time-saver, okay. Let me finish this simulation and we can move to the next step, okay.I'm just going to look at this simulation now, and once it's done we just look at the results real quick. Won't spend a lot of time. And then, show you how you can create the exact same system using a OpenStudio measure, okay. Almost done it seems, all right, perfect. Looks like the simulation finished successfully, no issues. You can see all those numbers. I have some heating consumption, here. I have cooling consumption. I have all the information, here. And then, I can check the unmet load hours, which is within the range. Looks pretty awesome.

Looks like the manual method worked fine to me. Now, what I'm going to do is, I'm going to remove, or actually, create a copy of this file. Save as, as new model. Let's say I'm just going to use some existing name here. The time is,let's say,9:30 underscore FCUs with DOAs OS measures, okay. It's a very long name, I know. But, like you know, just for like, you know, this class I'm going to name it this way. Save the model. The sophisticated way is to go to HVAC systems, remove all the unwanted information, and then run OpenStudio measure. A lot of times I just want the measure on top of the existing HVAC systems, it works ninety percent of time. But then, sometimes I get a lot of errors. If you are a new user I would suggest you to remove all the air loops and water loops. I'm not going to delete this domestic hot water loop, okay. But, hot water loop, yes, okay. And, if I go to thermal zones, I'm going to click on this ideal air load, okay. It will automatically remove my FCUsystems, you can see, okay. That's the most sophisticated way to work on your OpenStudio models.

There is a measure to actually install this ideal air loads just by one click, okay. But, I'm just going to show you the other measure that we have in our energy model. I hope you already has saved all the BCL measures on your computer. Go to your, apply measure, section here. Let's just wait for a couple of more seconds, okay. Go to HVAC, go to whole system, and the free measure that you get from BCL library is something like, this one.HVAC fan coil DOAS, you can actually use it, your exact same measure for radiant cooling and heating. You have for ground source heat pump, you have for water source heat pump. You can just like, play around with these measures. For now,I'm just going to use this simplest measure, which you have here. Apply measure now. Again, this measure is not very sophisticated. It doesn't allow you to provide a lot more inputs.But, you can create your own measure if you want. Or, you can always approach us in case you want a sophisticated version of it, okay. In that sophisticated version you can provide a lot ofinputs on this screen one, okay. Now it says that the building started with zero air loop and one plant loop. That one plant loop is for domestic hot water loop. And, it says the final condition, the model finished with two air loops, because there are two floors and three plant loops.

Eighteen zones are conditioned with zone equipment. All right, make sense. There is a heat recovery, as well. All the the air loops are 100% outdoor air system, which makes sense. Except changes now. And, you can see, in the zone side you have those air loops, they are dedicated outdoor air loops. And then, you have this four pipe fan coil unit system, the primary heating and cooling system. They are connected to hot water loop, as well as, chill water loop. If you go to the HVAC system tab, you can see that we have those air loops, as well as, chilled water and hot water exactly same, okay. Just like, try to grasp what we did here. Like, we actually created the exact same system within 30 seconds, exact same system, see,okay. If I run this simulation, it should work fine,let's see. All right. It is working fine. Please practice both the methods. You definitely should be able to create the HVAC systems using both the methods in OpenStudio. You should practice manual method, as well as, this automation method, okay. That's it for this this HVACsystem. I will catch up with you again for a different complicated system. Like, something, maybe ground source heat pump, or water source heat pump. Thank you.