The EMS Application Guide does have a set of example projects with a problem discussion, EMS design discussion, and EMS input object syntax for the EnergyPlus input file. If an example project doesn't showcase the specific EMS object that you are interested in (PlantComponent:UserDefined, in this case), then you can review the Input Output Reference documentation for that object to understand the input fields of the object that you can define. Most times after the input field descriptions there is an example snippet of input object syntax. However, this is usually for the object in isolation and doesn't show the other objects that are required to interact with it.

To see how an object interacts with other objects in an EnergyPlus model, you will want to review the example files. These are part of the EnergyPlus installation and should be found on your C:/ drive for the EnergyPlus version you installed (C:/EnergyPlusV9-4-0/ExampleFiles, for example). This folder is full of EnergyPlus input files (IDFs) created by the EnergyPlus development team to showcase different EnergyPlus objects and features. This folder also contains two HTML files that summarize information:

• ExampleFiles.html: for each example file, summarize the major features (location, HVAC system, etc.)
• ExampleFiles-ObjectsLink.html: for each object type in EnergyPlus, quantify how many example files contain the object and list the first three example files (alphabetically)

So, since you want to find example files that contain the PlantComponent:UserDefined object, you want to open ExampleFiles-ObjectsLink.html and search for "PlantComponent:UserDefined". You should find that there are two example files that you could review: EMSUserDefined5ZoneAirCooled.idf and PythonPluginUserDefined5ZoneAirCooled.idf.