15 - Thermostats - Heating and Cooling in OpenStudio

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For this session, we will talk about the thermostat settings, and zonal HVAC equipment, all right. So far we worked on space related settings, space gain, envelopes, and the geometry that we created in SketchUp. We are done up to this space tab here, on left hand side, which is like, blue, right now. Now, let's move to the next section, which is thermal zones. I'm just going to click on it. And, here you provide all these settings related to HVAC thermodynamics. You have to provide the thermostat settings, cooling and heating thermostats. If you have some kind of humidifiers, you can provide the settings for that, as well. You can provide the cooling and heating sizing parameters that we will discuss later, and so on, okay. In this thermal zone section, you can only provide zonal equipment. In case you want to provide air loop, you can also do that. But, we will talk about this later in the next session, maybe next week, all right.

For now let's just work on thermal sets. If you remember on day one, when we were working on the SketchUp, we actually provided the default thermostat settings to your computer. I'm sorry, to your energy model. For example, those are default thermostat settings are, like, here. Like, it has a medium office cooling set up, here, for cooling and for heating, here. Before that, I want to explain to you how this workflow works. On this left-hand side you can see all the names of the thermal zones. If you remember they're like, connected to some spaces, if you go to a space tab, here. You can see, they have like, thermal zones, here. You can either make changes right inside, here. Like, all the sizing and all. But, I would prefer to have a list view for my thermal zones. Which, for which I need to click on this thermal zone tab. And, that's where all these thermal zones are. You can either provide the ideal air load, which is already, there, in my computer. If you remember, on SketchUp, we actually provided the air loads, ideal air loads, to our energy model.

What is an ideal air load? Very important. Ideal air load is 100% efficient. It's always available and it's in, it has infinite capacity. People want to run the simulation with infinite capacity, 100% available, and 100% efficient HVAC system to understand the heating and cooling load in their project, all right. Here, you provide the air loop name. I will work on this air loop thing later. In zone equipment column, you drag and drop the zone equipment from library. You can see, there, like, a lot more options, here. Again, unit heaters, unit ventilators, PTACs, package terminal heat pumps, four pipe fan coil, energy recovery ventilators, dehumidifier, baseboards, and unitary system. Before we move further, let's just work on the thermostat settings. In these two columns, you provide the thermostat settings. It says, cooling thermostat schedule, and heating thermostat schedule. Same here with humidifiers and dehumidifier, all right.

In case you want to use the multiplier, you can also do that, here. What happens, a lot of times, in case you have a high-rise building and you just want to model 3 floors instead of, let's say, modeling like, 40 floors. You can use the multiplier method. What you can do, you will actually create the ground floor, which connects, which actually is attached to ground. Then you can create the top floor, which has an open roof, like, open to atmosphere. And then, you can create middle floor, just one floor. And, in case your floor number 2 to floor number 39 has exactly the same footprint, you can actually use multiplier. What we are going to do at the end of this session, or actually, the webinars, like, maybe in August. We'll run a quick energy model for a shoe box, as well.

But, for now, just for your understanding, in case you have that, this middle floor, you can actually provide multiplier, here. Like, this 38, let's say, it has only 3 thermal zones. And, that way you can reduce your workload. In case you have something like, a shoe box model, all right. For now, let's just like, you know, work on thermostat settings. Again, you need to provide a schedule. You can either bring something from library, like some very generic ones. Like, drag and drop, you know, like, how this thing works. Like, for example, if I want to drag and drop this large office cooling, I can do that. Or, I can just go to schedules and create something from scratch.

Let's go to schedules, here. Remember, very important, you don't provide any temperature related schedule in this section. You don't drag and drop here, okay. These schedule sets mostly are for fractional schedules, or for infiltration, okay. Go to this schedule tab, and let's just create something from scratch. Either you can use the existing ones, what I can do, I can actually go to this cooling, heating, cooling setup. Make a copy of it, copy of it, and make changes. Let's just get something from scratch, so that we know the complete process. Again, you can either add new object, or, from library, again, same thing. Just, drag and drop, here. Let's say, let me just show you really quick, so that we don't forget about this. Let me just bring something from rule set schedule. Let's say, this one, medium office heating set up.

Well, it already is there in our project. Let's bring something else, let's say, this small office cooling setup. Now, drag and drop in this tiny cube, cuboid kind of thing. I'm sorry, the rectangle kind of thing. And then, you can rename it. You can make changes. I'm not going to make those changes right now. I just want to do everything from scratch. I'm going to purge unused objects. And then, click on this, plus sign. And then, same window like, which, what you have seen in our previous class. The schedule tab, this time is going to be temperature. Look for this temperature, here. Numeric type is Fahrenheit, which makes sense, apply. And, rename it properly. Let's say, you want to rename it something like, office 101 underscore heating schedule, okay. Now, it has some generic values. Let's just assume from 12 a.m. to 8 a.m., let's say, let's just bring it to 8 a.m., here. The temperature for cooling is 80 degrees, okay. From 8 a.m. to, let's say, 12 p.m., let's just make it a bit, like, different. From 8 a.m. to 12 p.m., it's 75 degrees Fahrenheit. From 12 p.m. to 1 p.m., again, it goes to, let's say, 78. And, from 1 p.m. to, let's say, 6 p.m., it goes back to 75, okay. And then, it goes to 80 already, okay. This is our, like, schedule for 365 days. You can see the color of this default schedule is blue. If we apply this schedule to our thermal zones, it will be applicable for each and every day, all right. What if you want to change the weekend schedule?

Well, you already know the drill. You just need to click on this, plus sign, here. Add a new profile, okay. This is priority 1. And then, just select these days, here. Like, Saturday and Sunday, you can see the color for weekends change here to magenta. And then, let's say, for weekends, let's just do it for Saturday, for now. Just to make it more clear. Let's say, that day start on 9:00 a.m., here. You can just drag and drop in left, in right hand side, as well. 9:00 a.m. to 1:00, well, 4:00 p.m., the temperature is 75 degrees Fahrenheit unless, it's 80 degrees, okay. You can also create some step, step up or step down schedule, as well. A lot of times what happens during that shorter hour, the sudden drop, or sudden increase in temperature can always increase the unmet load hours. For that, a lot of people, what they do, they actually create something like, step-up schedule. From 80, it goes down to 78. And then, 75. Now, they're just going down straight to 75 from 80. And, same thing here, just change to 78 first. Bring your cursor on top of this horizontal line, and just provide some values from keyboard. 78, hit enter, or you can just like, you know, move your, move your cursor over this line too, okay, all right.

Let's keep it like this for Saturday. And, for Sunday's, let's create a new schedule. Priority 1, and just bring some values, here. Like, 80 degrees, and select this day as Sunday, all right. And now, it's always a good practice to provide some design day profiles, as well. In case you are planning to do some auto sizing of your HVAC systems. For example, for winters, let's just assume that when we can just create something from scratch. Right click, add. Let's say, like, you know, for winter, you don't want to be very specific about cooling, auto-sizing, cooling sizing. What we can do, just bring this value to 80 degrees, it's all right. And, for summers, we want to size our system to, let's say, 75, okay. All the time. That's our sizing works. You want to see the extreme value. What we’re gonna do here, we're gonna like, you know, actually, I'm sorry. Like, you can see the mistake, here. I actually named it to heating. But, I then, I created cooling by mistake. Well, we can, what we can do, we can just rename it, here, to cooling, okay.

That's easy. And then, what I'm going to do, I'm just going to make a copy out of, copy of it. Rename it to heating. I have all those patterns. I just need to change the values, again. For default, I'm going to bring this unoccupied time values to, let's say, 65, okay. And, for occupied, it can be 70. This unoccupied can go up to 65, again, okay. That's how my schedule looks like, for priority 2, which is for Saturday. Let's bring those values to 65, again, for unoccupied time. I can like, drag and drop. I drag my mouse, as well. Let's bring this value to 67, because we try to create the step up and step down thermostat settings. Let's make this as 75. And, for priority 1, make it to 60, for weekend. On Sunday, the temperature goes down to 60 for heating, makes sense, right. You don't want to waste your heating energy, okay. But now, a very important thing like, you know, when you do this, copy, paste. Make sure that you also change they design day profile conditions, too.

For example, for heating where winters are crucial. You want to actually size this for the extreme value, which is 70, right. And, for summer, it is, you don't want to care for heating for summer. This value can be 65, the lowest hitting point, okay. It will only look for the extreme value of heating, which is 70 degrees Fahrenheit. And, definitely the heating works, mostly for winters, most probably, right. I mean, it depends like, what is happening in your core space, and all. There are a lot of different things, I shouldn't generalize. But like, you know, you can play around with those values again, like, you know, so, you just got the idea, what I'm trying to do here, okay. I'm going to save my model, here. And, I have my heating schedule. I have my cooling schedule. I just need to apply these values to my thermostats. Click on this thermal zone, again. And now, if you remember, the schedules that I've created, they always live in my model, in rule set schedule.

And, that's where my schedules are. Like, office 101 underscore cooling schedule, and office 101 underscore heating. I can drag and drop here, on my first one. And, same with heating. Drag and drop over this heating column. And, either I can do it one by one, like this, which can take forever. Or, I can use this shortcut method. Just, like, you know, select all, here. Unselect these ones, which already have those values assigned. Click on this, cooling schedule. And then, you can see this, apply to selected, is live. This selected schedule is yellow in color. Apply to selected. These, all these blue ones are selected, blue thermal zones, apply. And, you can see it really saved your time, significantly. And, same thing with heating. Let's, let me just do it, again. And, you can see, it has like, you know, changed the thermostat settings for us, okay. I'm going to save this model, now. And, for this thermostat thing, I'll just stop here, okay. Thank you.