While we are looking at the Create Systems advance screen, it's a good time to check out some of the other features that can be changed here. The supply fan motor location can be defined here, though typically it's either going to be in the return or the supply. We also have the option to omit it. The return fan motor location is the same thing. The fan configuration can be set to blow through or draw through. While this isn’t going to have a significant impact on your model, it's going to affect your psychrometry, and should be taken seriously. The fan sizing method, the cooling coil sizing method and the cooling coil location are all located here. If you notice the warning in the corner that the fields marked in red are core components of the system. Changing these can drastically affect how well the system operates. Now, that’s very true for the fan configuration and the fan sizing method. If you have a good understanding of cool and coil location, sometimes this needs to change. For instance, in a fan coil system, it defaults to the room level. If you wish to zone it, you need to change this to the zone level.
We get options based on the system type for the other fields here, such as the supply air path or duct location. In this case we have return air or other. The return air path is a pretty important field to set here. It's typically either plenum or ducted. Further details on any of these inputs can be found by pressing the ‘F1' key in the help file.
For VAV systems, we can override the block cooling air flow, though I do not recommend that for beginning users. Finally, the other important field here is the ventilation duct location. In this case, we can tell the system how it delivers its air to the room. Typically it's return outdoor duct. This means that the ventilation mixes with the return air somewhere upstream of the coil.
The other option that’s often selected is room direct. This would mean that the ventilated is ducted separately from the supplier, and is dumped directly into the room. When the ventilation duct is room direct, it's important to note that the z ratio would not have to be specified when calculating ashrae standard 62.
There are some other options here, such as apply ashrae standard 62 people averaging. Typically we select no, but if there’s rapid fluctuation in the room population, you could select yes.
Finally, we can explore the option of what happens when we select ashrae standard 62 with ventilation reset. What this does, is it recalculates the amount of ventilation based on the number of people, and the people demand for ventilation. For instance, if you have 10 people with 10 cfm per person, you'd have 100 cfm at design. If the people schedule at any hour was set to say 50%, you'd only need 50 cfm. Finally, if we set CO2 based sensors in the room, we can set our CO2 based demand controlled ventilation. We can set that as none, proportional control, or single set point.
Typically, the control method will be specified and it requires much further thought. Otherwise, through the help file, you can access a more detailed article on proportional control and single set point control. If you are looking for an air side option, and you can’t find it under any of the other tabs, chances are that option, if it exists, is under the advanced option. The advanced options button is accessed under ‘Create Systems,’ ‘Options,’ and ‘Advanced Options.’