18 - Air loops and chilled water loops

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We are done with this hot water loop. We need to create one chilled water loop, now. And, for an air cooled chiller, you need not worry about a condenser loop. But, let's assume that for our system, we also have one condenser, or cooling towers. We go through two more loops here, two more plants loops. As I mentioned, first one is done. Let's create another one. You need to click on this plus sign, again. We need to start this plant loop from scratch, again. Empty plant loop, add to model. First things first, rename it to something like, chilled water loop, okay. And, fluid type is water, that's perfect. Maximum loop temperature. How much maximum loop temperature do you need for a chiller loop? Let's assume, 56. And, minimum can be 44 degree Fahrenheit. Maximum loop flow rate can be auto sized, for now. The most important thing that you need to take care of is in this sizing. A default one is, heating for loop type. We need to change it to cooling. Then design loop exit temperature, let's say it's 56. And, loop temperature difference, let's say, 12 degree, okay. I think that's very close to what ASHRAE’s is, but you can always check again, I can be wrong.

Next thing is, bring a pump. Same thing, same process. We are going to bring a variable speed pump, okay. We can make some changes here itself. You can provide some rated flow rate, maybe pump head, let's say it's 75. Let's change some motor efficiencies to, let's say, 0.85. You can change the efficiency curve, the part load performance curve. Pump control type, let's say, intermittent this time. And, the rest should be fine. The rest should be default, for now. Next thing that I need to bring one is, one chiller. Again, alphabetical. Keeps scrolling up. You have one absorption chiller option, you have indirect absorption chiller option, your electric ER option, okay. I'm going to bring one water based chiller, for now, okay. And, drag it and drop it, here. And, I'm going to bring one more water-based chiller in parallel to the first one. And, what if, if we have some secondary pumps? We can go to pumps, again. With pump alphabetical, again. And, you want to bring header pumps this time. Let's do headed pumps, like this. And, same with here, okay. Same with this first one. You, as per ASHRAE, sometimes you need to provide some secondary pumps, or primary pumps. That's how you do it. You can bring some additional pumps here, as well, in this node. But, for now, that's alright.

I'm going to change some properties, here. Number of pumps in Bank, 1 can be fine. You can, or, 3 can be fine, it's totally up to you guys. You can either bring this simple variable speed pump, as well. I just wanted to show you how headed pumps looks like, look like, in OpenStudio. Go to add it. Do you want sequential, that's the only option it seems. Pump head, fine for now, default. The rest is exactly the same information that you need to provide. What we did for this first one, first pump, the primary pump. I'm not going to spend more time on this, this headed pump, here. I'm going to jump on my chillers. These are chiller, water cool chillers. I'm going to rename them properly. That's a chiller 1, hard size or auto size, is totally up to you. Reference COP, this one is very close to what ASHRAE proposes. But, you can always change it. Let's say, my system, my COP of my chiller is very high. Let's say, 8, okay. Refresh. Leaving chilled water temperature 44 seems reasonable to me. Reference entering condenser fluid temperature, 85 is reasonable, again.

Then you have all those curves. Again guys, for chillers you need multiple curves. You need cooling capacity function of temperature curve, electric input to cooling output ratio function of temperature curve. Name electric input to output. Cooling output ratio function of part load ratio curves. Again, all these values can be given by your manufacturer, or, you can just go to the PNNL data, okay. All the information is default. Most of this information, for chiller at least, is as per PNNL, if I'm not wrong. But, you should always cross check, okay. These values seem reasonable to me, so I'm just going to jump on the next one. I'm going to rename this chiller 2, as well, okay. That's it. This time the COP  of this chiller is 6. My manufacturer, my facility manager, he decided to just change one boiler, okay. They can have different COPs, it's totally up to you. It’s totally up to your design.

The next thing that I need to bring is one set point manager. Again, I'm going to bring this outdoor air reset temperature. Drag it and drop it. Click on it. And, you can rename it if you want. These values seem reasonable to me, for chiller. Or, actually not. These are very, yes I can change them. Set point and outdoor low temperature can be, let's say, it can be 44, okay. Outdoor low temperature can be, let's say, actually no. Outdoor low temperature can be something, now, let's say, 50. Outdoor low temperature can be, I don't know, 60 or 70 or 75. I'm just giving you some random numbers based on my own judgment, okay. Don't, just make sure that you change, check all those values based on your design, okay. Set point and outdoor high temperature can be, let's say, 44. Outdoor high temperature can be 90. Seems fine to me, but again, please check, okay.

Next thing that I need to do is, I need to connect the cold water coil, the hot, cool water coil from my air loop to this pant loop. I can do it either through this air loop. Just go here, click on this cold water coil, and just connect it, here. Or, I'll just show you another way to do it. Go to chill water coil, click on, either on this splitter or mixer, and go to these options. Well looks like I'm wrong, I need to go back to air loop. No, actually not. I can actually show you another way. I know my ways. What I'm going to do is, from my model, I look for this coil, this cooling water coil. Remember, whatever components that I create by myself they always live in my model, okay. Drag it and drop it, here. Boom, see. And, if I click on this tin, link here, it will take me to this air loop, see. There's a shortcut. I have this chilled water cool, coil, chilled water loop, as well. I'm going to save my model before I move forward.