How the variable frequency drive sensors work in a model: place sensors, map them to cooling units, set a target pressure, and read the new reports.
This video demonstrates variable frequency drive (VFD) modulation of cooling unit fans in a raised floor model. The fans change airflow based on pressure or temperature sensors placed anywhere in the model. The demo model supplies about 66,000 cubic feet per minute (CFM) against a need of roughly 33,000 CFM, so it has a high pressure differential.
What the video shows
- Drag VFD sensors from the toolbar into the scene, from top view. In a raised floor room they default to under the floor. The demo places three.
- Open the connection editor from the right-click menu, choose temperature or pressure, and map all three sensors to a computer room air conditioner (CRAC) unit. The mapping can be copied and pasted to the other units.
- Turn on VFD data for each unit and set a target. The demo uses a floor pressure of 0.02 inches of water, then copies the settings to the other units.
- Save, run, and download the results. The report now includes a sensor report, which gives pressure and temperature at each sensor, and a VFD report, which gives the resulting flow for each unit.
- In this example the pressure reached was lower than the target. The units delivered about 20,000 CFM, well short of what the racks needed, so the Return Temperature Index (RTI) was above 100 percent and the Rack Cooling Index (RCI) was negative. The presenter uses this only to show how the feature works.
Tips
- The result will not always match the target exactly, because the process is iterative.
- Sensors can also be used as probes to read pressure or temperature anywhere in the model without connecting them.
- Saving over an existing name deletes any results already stored.