Everyone is looking for ways to save energy, especially if you’re a building owner. Well, one great way to save energy in a building is to install a Variable Frequency Drive (VFD). Hook this device up to a fan or pump and it helps to modulate the fan or pump speed to the minimum level that is required for proper system operation.
One common application for a VFD is in a Demand Control Ventilation (DCV) system. Essentially the fresh air being brought into a building, to dilute CO2 and pollutant buildup, can be reduced when a space is not occupied or is occupied at a level which is much lower than the space is designed to accommodate. This fresh air is often conditioned before being delivered to a space and the cost to condition this air is high. A VFD and DCV system will reduce fan power consumption and more critically, coil load. Depending on the HVAC system installed, this saves tremendous amounts of money.
However, fan motor selection can prohibit the use of a DCV system by limiting the available compatible VFD’s. Large single phase motors (1 HP or greater) should be avoided if possible, 3 phase should be used if possible. If a single phase motor must be used then the engineer should select them specifically for VFD use, if not then the DCV system will be in jeopardy. VFD’s for small fractional HP (3/4 HP or less) single phase motors are more easily obtained than those for larger HP motors, however attention must still be given to the motor selection to ensure compatibility with the VFD.
Need help with determining if a DCV is right for your building? Contact The Spinnaker Group today and we can help!
Building Commissioning Authority (CxA), Energy & Sustainability Consulting & Energy Modeling
By: Joe Fleming, PE, BEMP, LEED AP BD+C