In this lesson we're going to be modeling a make up air unit in eQUEST. This is sometimes called a dedicated outdoor air system. It's basically a system that delivers outdoor air to another system. There's actually not a direct way to model this in eQUEST, so we have to use what's called a work around. This is a common work around. It's used by users of eQUEST all around the world. The first thing that we're going to have to do is create what's called a dummy space and a dummy zone. We're just going to do this on the ground floor. Right click any space and create another space. We're going to call this dummy zone and we're going to create it from scratch. The shape is a box. It's just going to be one foot by one foot. That's all we have to do for the space. It's important to create the space first under the building shell.
The next step is to create the dummy zone. The dummy zone is going to be created under the air-side HVAC module. This is used to control the delivery temperature of the outdoor air. If we're not going to condition it, this is the control zone and we're going to tell it that you have a thermostat schedule that's not conditioned. Firstly, we have to create a dummy zone and we do this by going to the first system and right click and create another thermal zone. We're going to call it dummy zone. It's going to be conditioned. We have to assign it to a space. This is why we had to create the dummy zone space first. We select done. That's actually all we really have to do here. What would be a good idea is to set up thermostat schedules. This will control the temperature of the make up air. For instance, if you're always going to be cooling the make up air to 55 degrees, you'd want to set up a thermostat schedule so that you have make up air being supplied at 55 degrees. You could go through here and set up the rest of these, but since it's going to be based on the rest of the systems, we can leave those at their default for now. We click done.
This next step is interesting. We have to create another system. We're going to right click right on the first system and select create another HVAC system. We're going to call this the dedicated outside air system. This is going to be packaged variable volume variable temperature since the amount of outdoor air will vary and it's supply temperature can vary, as well. However, you could set this to really any type, provided that it matches the type of system you're trying to model. We click OK. We have to set the control zone, which is actually the dummy zone. Notice, we had to create the dummy zone and set it up in a different system at first. But now we have to move it. We click done. Here we have our system. The one thing that we want to change is we want to go to our outdoor air and set it up to have a ratio of one. The reason being is that this is going to supply 100% outside air. There's a number of other things that we can change if we know the capacity and the electric input ratio of this particular unit. However those things are no different than setting up a regular system, so we don't have to do that right now. In reality you would want to enter the correct parameters. If it has heating, you'll want to do this for heating, as well. You could even set up things like humidity control, just like any other system. Now we can click done as we set it up to supply 100% outside air. Now you see that we have the system at the bottom. That's dedicated outside air, and we have the dummy zone that didn't move yet. We want to double click on the dummy zone and set up the parent HVAC system to dedicated outside air. We click done. Now we can see that the dummy zone is located under the dedicated outside air system.
This next step is really important and a little confusing. We have to save the file and somehow we need to make this system appear at the top. The only way to do that is to edit the .INP file. I had saved this and now we have to close out of the file since we're going to edit the INP file. I'm cheating here. I already have the folder open. We need to select the INP file and edit it with a notepad program. I use notepad plus plus. It's a free program. You can download it for free and it never expires. I'm just going to do a control+F and find the dedicated outdoor air system. I'm going to click find next, and we can close. We need to cut this text out. I'm just going to use a control+X after highlighting it. We scroll all the way to the beginning of this section-- the HVAC systems. I'm going to paste it first. We can save this, close out of the notepad, and open the file back up in eQUEST. We're where we left off, except for the fact that the dedicated outdoor air system is now listed first. This is really important for the next step. If we click a system and we go to spreadsheet, we want to go to outdoor air ventilation and economizer. For the systems that are receiving air preconditioned from the other system, which is the most common set up, we can say the outdoor air comes from the dedicated outdoor air system. If this is for all of the systems, there's a quick way to apply that to all of the systems. If not, we can do it one at a time by selecting the down arrow. Instead we can right click on the second system, and we're going to edit/view the user default and set the user define default value to dedicated outdoor air system. We select OK. That will propagate through the rest of the systems. It will be in blue because it's a user default. Now we have outdoor air coming from this dedicated outdoor air system and controlled by the dummy zone applying to all of these other systems. If we look at the dummy zone, remember we can set up thermostat schedules to control the temperature of the outdoor air going into these other systems. Please don't forget to set up your other parameters if they're defined, such as the cooling capacity and cooling power of the dedicated outdoor air system. Remember we skipped all of those parameters so that we could focus on the general set up.