Small script allows to set up an orthographic VRay camera in the scene.
You can download it from here: VRay Orthographic Rendering Camera Rig
You just need to set it up once. The script doesn’t need to be loaded/running to render the view later or even on the different machine.
To make a top view just rotate the camera. It is possible to adjust position of the camera (with the rig) and its parameters (focal length and film width) without the script interface.
I needed it to render sections/elevations of a hotel room in my work. It worked fine. Camera cuts the model in the place where is here center (origin).
The viewport doesn’t show orthographic view. The scope of the render needs to be tested.