# 19 - Air loops and condensing loop

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## Script Preview

Now we are going to create a new loop. It's going to be a condensing loop. Again, click on plus sign. The process is exactly similar to what we did for hot water and chilled water loop. Create a new empty plant loop. Click on this, center dotted line. Rename it to, let's say, condensing loop. Fluid type can be water, that's good. Maximum group temperature, let's say, it can be 90 or 95, okay. Minimum loop temperature can be 85. And, you can change the loop type in sizing to condenser. Designed loop exit temperature, you can make it 90, 95. Again, these are not the values that I’m providing as per ASHRAE. These are as per my own judgment. Loop design temperature can be 10 degrees. That looks reasonable to me, for now. And then, the first thing that I need to do is, I need to go and find a pump. Click on pump, pump variable pump, variable speed, bring this primary pump. Then the second thing that I need to do is, I need to bring condense cooling towers. I have variable speed cooling tower option. I have cooling tower single speed, two speed.

Let's bring something like, variable speed. Again, you have some other options too, for variable speed. Cooling tower cool tools, York calculation. Let's bring this variable speed cooling tower, which looks very reasonable to me. And, I can bring another one in parallel, then I can bring some secondary pumps. Again, very, like, exact same process that we did earlier. These are secondary pumps, here. You can see. And, what if you want to bring some bypass pipe? We can also do that. Where is the bypass pipe, this one, adiabatic, okay. Again, the adiabatic pipe needs to be the bypass pipe. In case you have some pipe installation or something, let's say, you have outdoor pipes, here. There’s some piping that is going through outdoor conditions. You can bring it here, this outer pipe, click on it. You can provide inside diameter, pipe length, the pipe construction. You want to check this pipe construction, go to constructions, here. Click on constructions, and look for this pipe construction option, here. It has one pipe steel, here. Pipe steel is a material, go to materials. Find pipe steel, and it has its own thickness conductivity and everything, okay.

You can do a lot of things in OpenStudio, as I mentioned to you earlier. You can provide your installation as per these given values. Go back, back to HVAC. Look for condensing loop. Click on this outdoor pipe. You can change the length, let's say the length is only 100 feet, all right. Pipe diameter is, let's say, 3 inch, or let's, 2 inch should be good, 3 inch is quite bigger, okay. Go back to library, again. You have option for, let's, you have option for inside pipes too, like exactly the same way that we did for outside pipe. Let's bring some set point manager. This time I can just bring one schedule, should be okay. Let's bring this schedule, chilled water temperature, click on this. The schedule that we use is chilled water temperature, which doesn't look very reasonable to me. I want to provide the set point manager scheduled temperature values somewhere around 85. I want this to run at 85 degrees Fahrenheit, for condenser, which is a reasonable value. Go to schedules, find the chilled water temperature. You can be see the value is 44, which is not reasonable. I'm going to rename it to, let's say, condensing, condenser set point temp, okay. And, change it to, let's say, 85, okay. I mean, it varies. It's some, like, number that I find reasonable. Don't like, think that this is the only number that you can use. It can vary as per your design, okay.

Again, whatever values that I give in this class, don't rely on that. Always use your judgment. I'm here just to show you the workflow here, on OpenStudio, okay. Condensing loop, what else? We have this condensing set point temperature schedule. We have everything, here. Again, we need to connect it to one, through this chilled water plant loop. How you do this? Either you just go to chilled water loop, go to these chillers. Connect them, actually, you can't do it, here. How can you do it? Just go to condensing loop here, in my model. Find those chillers, here. Drag it, and drop them here, okay. Now you can see, you have those chillers here. They're connected to your loops. Both these loops are connected. Basically what is what it is doing, this air loop, this VAV water based air loop, these coils are connected to one loop. These loops are, here. If you go to chilled water loop, then this chilled water loop is also connected to condensing loop here, okay. Just think about it. Just try to imagine it as a loop of multiple sub loops, okay.

There's one loop for condenser, one for chiller, both of them are connected. Both of them are interconnected. There is a separate plant loop, which is hot water loop, that is connected to air loop. Even a chilled water loop is connected to air loop, okay. Just try to assume what is happening here, okay. We have everything here to run this simulation. We can save it, okay. And, if you go to this thermal zone tab, here, you can see this, that only floor one thermal zones have this air loop, okay. We can run simulation right now. We have some package terminal heat pumps. We can, we'll be fine if you run this simulation. But, what if we want to have an air loop, as well. Even for floor 2. What we can do, we can create a new plant, air loop, real quick. I'm going to show you, here. How you do this, it's a good practice for everyone. Click plus sign, go to an empty air loop dotted line. Rename it to, let's say, floor 2, floor 2, I’m sorry, floor 2 VAV loop, air loop. I want to like, you know, name things properly so that you guys don't get confused. In sizing, I can, looks like sensible, it's alright. I can change this 100 person outdoor in cooling and heating, to no. Now, this is fine. I can move to the next step, which is, bringing a fan. Let's go to a variable speed fan, drag it here.

You can change the values if you want, I'm not going to do it. The next thing is one outdoor air controller, which is, this one. Outdoor air, or this is a dual duct, we can go to this air loop outdoor air system. Drag it, drop it, here. Let's assume that this outdoor air controller has some kind of heat exchanger. Remember, for the, for our previous class, in two weeks, in this session that we did two weeks back, you also provided some latent heat exchangers, latent sensible heat exchangers to do some heat recovery. Let's do that here, as well. I'm just trying to find one, that component, this heat exchanger that’s air to air sensible and latent, okay. ERV heat exchanger should be fine, drag it and drop it, here. You can see, there is an heat exchanger happening. You can change the properties of this heat exchanger. We did it in our previous class, so I'm not going to do it again. The next thing that we need to bring is one hot water coil and a cool water coil. Let me just find it, here. This one is hot water coil, drag it and drop it, here. And then, one cool water coil, here, okay. And now, the next thing is, I need to bring one set point manager. Set point schedule should be fine, for now. This one, this should be fine. Deck temperature, you should always check that deck temperature. I know the default one is 55, which seems to be stable to me.

And now, I need to connect these primary coils, here, to my plant loops. I can just connect to existing ones. Click on them, and click this, hot water coil to the hot water loop. Make sure that you just connected to hot water loop, not chiller or condensing, okay. A lot of times people do this mistake here. And, even for cool water coil, connect it to chilled water loop, okay. And now, I can provide some diffusers. Let's say, we will go with something like, VAV with reheat boxes. They are fine, for now. This one, the most common system and you should totally understand how this works, okay. They are different kind of reheat box, electric, which is very simple. It has electric reheat coil. You need to know to connect it to any plant loop. You have gas, reheat coil, it is connected to a gas furnace. Let's bring this hot water reheat, click on it, go to links, and connect it to hot water loop. Now, click on either splitter, or mixer. And, just select all the remaining thermal zones.

Okay. Took some time. Just to verify it, just click on some random boxes and see if they are connected to hot water loops. Looks like it is fine, okay. I'm going to check it one more time. Go to chill water loop. You can see two primary cooling coils, make sense. Go to hot water loop. You had two primary heating coils and lots of reheat coils. Go to thermal zones there, and see if all of them have some kind of air loop. Looks like it. I'm going to save the model. And, we are good to run the simulation. Let's do that.