16 - 2 Zone HVAC systems: Part A

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´╗┐Hi everyone. This is a Harshul Singhal, again. Let's talk about thermostat settings, again. Or, actually the sizing parameters for heating and cooling. We talked about putting thermostat, here. We talked about ideal air loads. Let's talk about some sizing parameters. For example, if you click on, cooling sizing parameters versus sizing parameters, they are kind of the same. For example, in cooling sizing meters, you have the name of thermal zones. Then you have cooling design supply air temperature. Again, it's for sizing.

The default value is 57. Let's assume, if you want to, make it 55, just change it at one zone, select all, click on this, 55 degree Fahrenheit option, again. And, you can see this, apply to selected, is live. Click on it. It made changes for all of them. You can change the design supply humidity ratio, in case you want to cooling, in case you want to change the sizing factor. You can also do that.

You can change it for the total like, everything, like, all these zones. Just by like, changing in these settings. Like, if I go to settings, here,simulation settings. You can change cooling and heating sizing factors. Like, these are the default values based on ASHRAE 90.1 guidelines. For heating,it's 1.25 and cooling is 1.15, as per ASHRAE 90.1 guidelines, in case you need to create the baseline model. But, in case you want to change the cooling sizing factor, or like, heating sizing factor for some particular zones. Let's say, for this one. You can do that directly here, okay. This is like, 120%, which means, 20% extra. You can change the minimum floor area, flow per zone floor area. It depends like, what is your cooling design airflow method. Like, for example, if you want to change flow by zone, like, you can provide the values, here. Like, the most like, used parameter here, for design airflow method is design day. And,that's when the design day weather file is used, okay.
If you are running a baseline model, I would ask you to use this design day method. Then you need not to worry about all other parameters, here. Like, for example, the first one is flow per zone. You need not worry about filling this one, okay. If you make something like, design day with limits, well, like, you know, I would prefer, I can use this design day. In case you want to read what these different parameters do, you can always go to EnergyPlus documentation. Go to input/output reference, and you can do a quick search, here. For example, what if I want to look for something like,let's say, cooling minimum airflow fraction. Let's say, what it does. I can just perform a real quick search, here. It used to be a different version of the input-output reference, or actually, this documentation.But, now they have created this PDF for you, which I personally don't find very user-friendly. The previous version was more friendly. But, it is what it is right now. Let's say, we want to do something like, cooling sizing factor. Again,like,it's searching through PDF. It can take some time.

Let's say, I mean, it can take some time. I know like, you can, you can see this, it has like, 36 of those parameters. I mean, now you need to go through all of them on Y-1. But, you can see, this is the cooling sizing factor. Like, you finally can figure it out. Let's say, like, if I want to go through what is happening in this section. You can see this is for sizing, here, you can see. And, what if I want to look for cooling sizing factor, here. It says the input is a zone level cooling sizing ratio. The zone design cooling air flow rates and loads will be multiplied by the number inputs in the feed, okay. Just wanted to let you know that like, you know, how can you read more on these inputs that you are trying to provide,here. In case you have any confusion,you can always go to unmethours.com. That's another very good resource for help, unmetshours.com. Oh, sorry, unmethours.com. This one. You can login. You can always ask questions. For example, if I want to look for cooling sizing factor,let's see if they have some questions related to that. You can find some questions.

For example, if I want to look for something like, ground source heat pump, okay. You can see, there like, a lot more questions on ground source heat pumps. For example, if I go on this, they have some questions. And then, people are very active. Somebody will definitely reply to you within like hours or something. In case you don't find your question, you can always ask a new question.

Everyone, including me, is super active on this group. Definitely, you will find the answer of your query, okay. The most important thing that I want to explain is, this design zone air distribution effectiveness in cooling mode. You have similar inputs here, as well. What is this? Well, what happens, the, these inputs are used for EnergyPlus designed day sizing routines. You need to provide values like, those sizing factors, here. You can also provide some distribution effectiveness. It is governed by ASHRAE 62.1 standard, which talks about it's zone effectiveness calculations.

For example, like, you know, if you look, if you go through ASHRAE 62.1, you will find this air distribution concentration. The default value one is for a distribution, something like, what you have from ceiling. If you have ceiling supply of cool air, then the ratio is 1. Let's say, if you want to have something like, displacement ventilation. It actually increasesthe distribution effectiveness. It will basically, it will act as a site, as a saving on your project. It says, if you have floor supply of cool air and ceiling return provided low velocity displacement. The effectiveness increases,which is amazing, right. If you are trying to model something like, displacement ventilation, you should change these values to 1.2 or like, you know, based on 62.1. And, it will bring more savings on your project. The default one is one, which is ceiling supply of cool air and ceiling supply of warm air floor return. Which makes sense. If you have something like, makeup supply drawn in on opposite side of the room from the exhaust and or return. It means the effectiveness reduces. You need to change the effectiveness ratio to 0.8, okay. Same thing with cooling.

Again, like, make sure that you provide these appropriate sizing factors, or sizing values, before you are in this simulation, okay.I'm going to run the simulation and jump on the next thing. Which is, how to implement the zone equipment. First thing I want to show you, that like, right now, all of them have ideal air loads. Like, we created some of them later. That'swhy they are unchecked. But, when you run the simulation, in reports. If you go to EnergyPlus results, and then, scroll down to end uses energy consumption. You can see, there is no energy consumption for cooling and heating in this electricity and natural gas. If you use something like, ideal air load, they come as, district cooling and district heating. Well, again, as I mentioned, they are always available, 100% efficient, and infinite capacity. And, that's why they act as district heating and cooling.

What if, if you want to provide some real HVAC systems. Go back to your, the thermal zone site. And, look in this library. You have a lot of zone equipment, as you can see, here. Zone equipment can be something like, single zone HVAC equipment. They can be forced air systems,like, PTAC, package terminal heat pumps, fan coil units, unit heaters, as well as, VRS, variable refrigerant systems, all right. And then, they can as something like radiator systems or convective systems, like, baseboards or radiant floors. Either they can be like, you know, package systems, where you have the heating and cooling coil within the system. Or, they can also be connected to a central plant with their piping, all right. Let's create something very simple, here. Something like, exhaust system. Look for fan zone exhaust, which is here.

Again,it's the same workflow. Just drag and drop, here. In the zone equipment side.
I'm going to draw, drag them, like, drag one of it, and drop it in the first zone. And, click within this, this name. You can see, this is a yellow color, which means it's active. And, on the right hand side, you will see, you can have, you have this edit tab. Which means, you are allowed to edit the system, here.You can provide some kind of schedule. You can provide the fan efficiency. These are some default values. You can change them easily. Let's say, if you want to provide a pressurize of 0.5 inch. Yes,let's do that. Maximum flow rate. Let's just, like, you know, provide a maximum flow rate of 50 CFM. You can provide some schedules, some more schedules. You want to couple it with the system. Let's not couple it. This says decoupled it.

What if, if you want to provide an on-off schedule for this zone exhaust. Let's go to schedules. In schedules,let's get a new schedule. Look for something like, on/off, hit apply. Rename it to something like, exhaust schedule. And, for exhaust schedule, zero value is always off. And, one value is always on. If you put anything between zero and one, the model might not like it, okay.

Make sure like, you provide either zerovalue, or one value for the on/off schedule. Let's just assume that exhaust is running from 8 a.m. to 4 p.m., always. And then, the rest of the time, it doesn't run at all. I think that's good for now. You know how to provide the schedule for weekends and some specific days. I won't go into that much detail. You can also provide designed day profile, and all. Let's just go back to thermal zones, again. And, in this zone exhaust equipment. First, like, rename it to something like, EX1. And, provide some like, schedule here, like, availability schedule. It can be something like, what we then, we renamed it to exhaust schedule, all right.

This exhaust will run only from 8 a.m. to 4 p.m. Like, those on/off schedule can constraint the workability of your systems. Very important. Now, you can like, you know, copy exact same exhaust for the rest of the,let's say, restrooms. I'm going to select restroom, here. And, there should be one more, this one here. Select this, and apply to select it, here. Click on this. And, you can rename them, you can make some changes, it's totally up to you. I always like to rename them properly. Let's make some changes in the properties. Let's say, the fan efficiency here is 80%, so0.8. Pressurize, let's say, it's only 0.25. And, if you go to next restroom,you can rename it to exhaust 3, again. You can just keep the same schedule. You can just change the schedule, it's totally up to you. You can provide a lot more details, here. But, for now, we are good. We can run the simulation, here. Or, what we can do, we can provide more values. We have provided the easiest zone equipment, which is the exhaust schedule.

Let's provide something like, let's say, unit ventilator, okay. Let's do that. Let's assume that the IT room has a unit ventilator, only for cooling, okay. Let's just drag and drop this first option, which is unit ventilator constant fan cooling. There are a lot more options. Variable cooling,variable heating, on/off heating, on/of cooling. Let's just start with something like, constant cooling. Drag and drop it to IT room.And, when you do that, you, you'll realize that the ideal air load will automatically be gone. See, see, this mark, this thing is unchecked now, okay. Click on this, again. You can rename it to, let's say, unit UV-1, and you can provide the schedule. Same way, let's assume that this one always, whenever it's, it needs it. If you provide, something like, always on discrete schedule, which are one of the default schedule that you have in your model, you can't edit them. They're like, stay in the background. But, if you provide them, it means whenever the cooling is needed, the system would work.

You can always provide on/off schedule to control the workability of your system. But, if you provide always on discreet schedule, it means whenever the cooling is needed, that's when the system would work. Which makes sense, right. You can hard side the system. If you auto size the system, it will always use a design day profile values, okay. Let's just hard size it to, I don't know, 3000 CFM's. Outdoor air control type, you can either providea fixed amount, or variable person. Let's just provide a fixed amount of, let's say, 50% of, let's say, 20% of total airflow, which is 600 CFM. Again, I am using very like, random numbers. Don't count me on them, okay. Then you can always control the minimum outdoor air schedule, as well. You can provide always off schedule,that'swhat the default is.Or, always on discrete. Either way, you can provide on/off,it's totally on you, what you want to do. Let's provide on/off always on discrete, for now.

You can hard size or auto size it. And,you can provide a lot more values.
For example, if we scroll down, you have a constant fan attached to this unit ventilator. Which makes sense, right. It's a constant fan. You can control this fan. For example, if I provide this always, I'm sorry, this exhaust schedule, remember it works from only 8 a.m. to 4 p.m. It will also govern this schedule, this fan schedule will also like, constrain the workability of your unit system, okay.Keep scrolling down. You can see it needs some kind of cooling coil for water. As well, and, as well as some properties associated with this. Right now, we don't have any plant loop. And, it asked you to connect this cooling coil to some, one of the two either, chiller or any like, you know, air loop. Which has some kind of cool cooling supply, okay. Since, like, we don't want to cover any plant loop for now, for this session. I won't like, you know, explain a lot more, here.
But just wanted to let you know that, you know, if you want to connect these cooling coils, they are like, some links, here. You can see there are like, some like, like, new features, here. For particularly for this unit ventilator. If you click on them. For cooling, it asks you to connect it with some, one of the plant loop. Again, I shouldn't have selected this unit ventilator, because it needs a plant loop. What I'm going to do, I'm not going to confuse you, for now.I'm going to select something, which is more simpler, which has its own DX coil, DX electric coil or something. I don't want to create plant loop for you guys for now. Because,you'll be super confused. Let's just like, forget this unit ventilator.I'm going to click on this, UV-1, again. And, click on thiscross mark, here. You can see on top right, click on it. And, it will delete the UV-1 system for you. Go to library, again. And, look for something where you need not to worry about a plant loop.Let's say, PTHP, package terminal heat pumps, package terminal heat pumps. Sorry guys, my English is not that great.

Drag and drop it over one of the rectangles, here. Let's say you want to assign it to conference room 3, here. And, rename it to PTHP-1. Again, click on this. And, it will, like, make this edit tab live. You can rename it PTHP-1. You can, again, provide the schedule, here. Like, when you want it to be available. Let's say you want to make it available, again, from 8 a.m. to 4 p.m., something what we gave for exhaust, okay. You can keep things, keep either auto size, or you can provide some values. There are a lot more things, here. In case, again, if you are always confused what is happening, here, you can search these terms in that EnergyPlus documentation. It will always help you down for the calculations. How the workflow works. How the calculations happen behind the background,okay. If you keep scrolling down, there are a lot more inputs that you need to provide. Like, sometimes, the default ones are like, you know, more than enough.

For example, hey, like, cooling convergence tolerance 0.001 looks fine to me. And, what if you want to change something for constant fan. You want to change efficiency. Well, feel free. Then the next thing is heating DX single speed coil. Again, these are templates. You can't do a lot more changes, there. Like, in case, For example, if you want to change it to speed, you can do it here. But, there are different HVAC systems, here.From library, you can bring them. You can provide a COP, here. Let's just assume the COP is 3. It'sa very bad system. Yeah, there are some efficiency curve, heating capacity, function of temperature curve. You need to provide those values to their sum of the values, which are default. We'll see them when we scroll them down. Then these are the curve values. You can always change them. In case you want to understand from where you can get these values, either you can use these default values. Although, for something like EnergyPlus documentation, just Google PNNL 25130.

Look of first documentation. And, this document helps you out to provide some inputs related to curves and a lot of other values,okay. For example, in this table,here. Let me just find it for you guys. You can see,they're all like, EIR values, coefficient values, and all. Like, this documentation is very helpful to understand. Like, you know, none of the properties that you need to provide for your chillers, for your boilers, for your fans, and a lot of other information. Please go through this documentation, as well. I mean, if I really want to explain this documentation to you from page by page, it can take forever. But, again, it's a very great resource to understand the inputs and how to provide values. For example, like, if I click on something like,let's say, let me just find something important for you. Let's say I want to like, understand how the EIR function temperature coefficient works. Like, one of the values. You can see, these are the values for scroll chiller, reciprocating chiller, screw chiller. You can provide these values to the curves here, okay. You can change values, here. I mean, this is coil curves. But, again, you can do it for chillers. There are values for coils, as well.
Keep scrolling down. There are a lot more curves, again. And then, there's single speed cooling coil.

Same thing, you can change the COP. Again, a lot of curves here, okay. This is one of the zonal equipment, which you need not to worry about having a plan two, okay. You can, if you click on this, link tab. There is no clink, no linkage needed, okay. What you can do, once, either you can just, like, you know, bring newer or different systems in each and every zone. Or, what you can do, you can just select,select all, here. Uncheck this, conference room 3. Click on this PTHP-1. And, click on this, apply to selected, here, okay. You can see, now this, this project has package terminal heat pumps for each and every zone. What I can do, I can save it, and run this simulation,okay. I'm going to run the simulation. And, for next class, we'll work on some other systems, okay. Thank you.