24 - Domestic hot & cold water

Learn OpenStudio Now in one of these online courses:

Script Preview

´╗┐Hi everyone. Now let's talk about domestic hot water systems. In OpenStudio, domestic hot water systems have their own templates, in the HVAC system tab, here. If you look at these options, here, like, the first one is service hot water template. Second one is refrigeration template. And, the last one is VRF. Let's go back to service hot water template and understand what is happening here. Here in this template, what it says, your supply of fresh water, here.

The fresh water goes to your connection,so, building connections, water connections. And the remaining, the water, the extraction goes to either municipalities, gray water connection, or black water, okay. Good thing in OpenStudio you can actually calculate hot water, as well as, cold water, okay. Cold-water consumption. You need not to just heat up all the water usage in your building. You can have two different connections. One for hot water and one for cold water.

Let's work on it.I'm going to bring one water use connection in my building from library. Drag and go down, in water use connection. Drag and drop this first connection, which is going to be hot water, for now. Click on it. And, it will take you another loop.

You can see it here, you need to provide some water use equipment in your building. You have water use connection. Your water use equipment, now.You can have multiple equipment. One can be for cold water, one can be for hot water. You can just separate them out, if you want.I'm going to bring one water use equipment in my building, here, from my library. Water fixtures, again, click on these water fixtures. You can rename them. Let's say, I want to rename them as hot water consumes total, okay. And then, you need to provide some water use definition. There is one default, which it creates by itself. You need to provide a space name where this hot water, these hot water equipment are located. Let's say they're located in a restroom. You can create like, different, or multiple equipment if you want,it's totally up to you. And, you can provide some flow-rate fraction schedule. Let's say I want to change this water use equipment definition. I can go back to my schedules, and I can look for this water schedule that it created for me, the default one. I don'tremember the name actually, it seems. Let me see. Where is my schedule? I can just purge. There so many unused schedules, it seems. One which I'm looking for is, this, I don't know why I don't see it. Let me just go back to my loop again and see what was the name. Again, the thing is, this different kind of menu that you see in OpenStudio and sometimes you can get confused.

You can see the equipment definition is watered fixture definition. And again, I was looking into schedules. That was my mistake, sorry about that. You need to look into definitions. Here are your definitions in loads. Go to loads. And, remember I told you that I'm going to explain to you what to use the definitions later. That's the time now. The default one is 1.00155 gallon per minute. Looks reasonable, for now. You can increase it or you can reduce it.I'm just going to keep this one, for now. Then, you can provide the target temperature schedule. Well, let's say if it's hot water, you can change the temperature schedule, the target temperature schedule to, let's say, 120 Fahrenheit, all the time. What I cando, I can go to my schedules. Create a new schedule for temperature, hit apply. Rename it to,let's say,TargetDHWtemp, and make this value to 120. You know all those schedules, how do they work. In case you have any confusion, please go back to my previous videos.I'm going to provide some design day profiles,as well. For both summer and winter. Go back to my loads. Go to water use equipment definition, and just drag and drop this new schedule from my rule set schedules in my model tab, okay. From my model tab to this tiny rectangular box.

The name of my schedule TargetDHWTemp, drag and drop. Now, what it says here? It says that, hey, you gonna have a peak flow rate of 1.000155. Let's make it simpler, here. One gallon per minute at a target temperature of 120 degrees Fahrenheit to all my water equipment, okay, in that particular restroom. Go back to my HVAC systems tab. Go to this first water use connection. Go to this hot water total. And, we already have definition, here. We have a space name. What else do we need? We need a fraction schedule. We can provide something,let's say, in schedules. Let's say, we have some schedule, the fraction schedule. Water is zero most of the time, until 8:00 a.m. Then it goes to,let's say, 50%,0.5, between 8 to 9. And then, 8 to 10 it goes to 0.4. Then,let's say, from 10 to 12 it goes to 0.3. Then during lunch break it goes to 0.75.

Then from 1 to 3 it goes to 0.3, again. And then, when people start leaving they start using the restroom more. Let's say, it goes to 0.8 now, okay. That's my water consumption schedule for hot water. Looks reasonable for me.I'm gonna assume it's just for weekdays. I need to create a new profile. You remember how you create those profile. Just assign Saturday and Sunday to that. And, just assume that the water is used only for one hour, up to 0.5 between 8 to 9. And then, 4 to 5, it's just a random schedule that I'm trying to create, okay. Saturday, Sunday havea different profile for consumption compared to weekdays, okay.

Go back to your HVAC systems tab. Or, actually, I should have renamed it properly, that's my mistake. Let me just go back to schedules, again, and rename that schedule that I created. It's DHWflowrate schedule, okay. I know what I'm doing, here. I mean, definitely you should rename your components properly so that you know what you're gonna do in the future. In case you need to troubleshoot your model, these proper names, or nomenclatures, definitely help you out. I'm going to provide this flow rate fraction, here. The one which I created just now, which is domestic hot water flow rate schedule, okay. Now, this equipment uses one gallon per minute as peak rate, at a temperature of 120 degree Fahrenheit, for this floor one restroom. And, it has its own fractional schedule that we created. What if we create another equipment that uses only cold water. Again, go to library, and create new equipment.I'm going to rename it to, let's say, cold water consumption, cold water fixtures, okay. And, it created one more default schedule for me, or definition for me.I'm going to assign it to, let's say, floor two restroom. Flow rate can be the same which I created just now. The only thing that I need to do is change this water fixture definition one.

Go to definitions, or loads. Rename the first one. I can rename this one properly, as well. I would say, hot water fixture definition, which looks more reasonable to me, right. And then, this one can be cold water definition, CW, should be fine. And, let's change this peak flow rate to maybe, 0.5. Now, target temperature, we can provide a target temperature of,let's say, 55 degrees Fahrenheit. What will happen eventually, the heating won't even kick. It means that whatever water that you are getting for municipality will be used as cold water. A lot of times people provide value, something like, 85 degree Fahrenheit or something, and the municipality of water temperature is 80 degrees. It means there is some heating happening, which you don't want to let happen on your project, okay. Make sure that you provide some very, like, you know, crazy number for cooling so that the heater won'teven kick in, okay. Go to schedules, again. Create a new schedule. Again,it's going to be a temperature schedule, hit apply. And, you can rename to something like, CW target temperature schedule. And, I can make this temperature value to, let's say, 55, okay. Same for winter, I can just use the same default schedule for winter and heating somewhere, as well.

Go back to your definition, and provide this target temperature from your, my model, okay. Now we have two separate definitions. One for cooling, one for hot water. One for cold water and one for hot water, sorry about that. And, go to HVAC systems, again, the tab. And, just QC your equipment one more time. This one is for hot water total, makes sense. Hot water,water definitions, space name, flow rate, seems fine. Click on the next one. Cold-water definition, flow to rest, seems fine to me. Now, what we need to do is, we need to assign these water connections to your hot water loop, plant loop, okay. You need to have a plant loop, as well. What I can do, I can go back. I can go back to service hot water and click on this plus sign, again, okay. Click, create one empty plant loop, it's going to be similar to what you did for hot water loop. Again, click on this dotted line. Rename it to something like DHWplantloop, or loop should be fine.And, fluid type, water is fine. Maximum temperature,let's say, it goes up to 150. Minimum it goes to, 120. Flow rate, I'm going to keep it for default, loop type is heating, make sense. Design exit, 150. Loop temp, 30 should be fine.once I am done with sizing, I can start bringing other components.

From the library, I can bring a pump first. Pump can be variable speed. You can change the values.I'm going to keep them for the default one, for now. The next thing I can bring some setpoint manager. I can bring the schedule one, the default, the easiest one, this hot water temperature. And, I can check, or I can QC the schedule first.This says hot water temperature for set point manager schedule. Go back to your schedules and see what it says. The deck temperature, okay. Where is deck temperature,I'msorry. I think it says hot water. Hot water is 153. I can change to 150. Same for winter, 150. That's what we want from our heater. 153 was also reasonable, but let's make it precise. Go back to your HVAC systems tab. Go to your domestic hot water loop, this is changed. The value is changed 150 degree Fahrenheit for setpoint manager. Let's bring one heater now, okay. We need to bring a heater, water heater. You can see you had different kind of heaters. You have water heater pump, you have water heater mixed, certified.I'm just going to bring this water heater mix, drag it and drop it.
This is the easiest one. Click on it. You can hard size it, you can provide this tank volume, which is 100 gallon, as default. You can change this water temperature schedule name. I would like to keep the same value, what you give provided to set points, change it to hot water temperature.

Deadband temperature difference, seems fine. Maximum temperature limit can be 150. Heater control type cycle, okay. Maximum capacity,it's quite higher. I will just keep it, now. You can auto size it. Natural gas, fueled, heater fuel type is natural gas. You can change your electricity. If you change to electricity, the efficiency will be 100 percent. But, if natural gas, you can change the heater thermal efficiency, as well. You can provide a part load factor curve, as well. And, you can provide some on cycle parasitic fuel type. The pilot load, you can provide some ambient temperature indicator. Let's say, if you have this boiler placed outside, or inside, in a thermal zone, you can change the thermal zone, here. Let's say, ambient temperature indicator, right now, the default one is schedule. That's why they have provided a default schedule, here. What if I change to thermal zone? Then you need to provide a thermal zone, here, where this boiler is capped.

Let's say if I change this ambient temperature indicator to outdoors, then none of these values are used here in this simulation, okay. Let's keep windows outdoors, for now, as ambient temperature indicator. Keep the scrolling down. You have use flow rate fraction schedule name. And, a lot of other values. Most of the important ones I already have taken care of. You can change the end-use subcategory if you want to. Let's say, it can be something like, domestic hot water, okay. It gives you a proper nomenclature in your result. And now, you need to provide something in the mine equipment sign. Go to my model. Scroll down to water use connection, and drag it and drop it. Even if you have one cold water equipment attach to this connection, it won't affect that particular amount of water that has been going to cold water taps, or faucets, or WCS, because, the target temperature for those cold water equipment is quite low, okay. It's fine for now. Save the model. And, we can run the simulation, but looks like this model doesn't have any HVAC system. What I'm going to do, I'm going to apply one measure real quick. One more time for you guys. I want to show you how the final numbers will look like, because in my next video I'm going to show you how to process the information that you get from your OpenStudio model. Go to HVAC, whole system, and run something real quick for you. I'm going to run VAV with reheat, again, one more time.

That's the easiest, and like, you know, most used system in OpenStudio.Apply it. And, it's, it will take maybe like, 15 seconds or something. As I mentioned,it's like magical. It does all the work for you within 30 seconds. The amount that you use to create a VAV system is somewhere around one, two, three, four hours. But, these measures can reduce your work load significantly, okay. Now I have this VAV system, now.I'm going to run the simulation. And, we will troubleshoot the results for you one more time. And, we will show you how to post process the data that you get from OpenStudio model, okay. Well, thank you. Thanks so much guys.