An effective energy management tool for HVAC systems is the variable frequency drive (VFD). When VFDs are installed on fan and pump motors, energy savings can range from anywhere between 35 to 50 percent over conventional speed applications. VFDs can be installed in pretty much any HVAC application in commercial buildings.
Although building loads are not constant, most building HVAC applications are designed to operate fans and pumps at a constant speed and for peak load, which over-sizes the system for most operating hours. VFDs improve operating efficiency by operating at less than full mode. Energy savings are achieved by matching system capacity to the actual load, with the most savings generated from applications that require variable speed operation, such as variable volume fan systems that distribute conditioned air. Additional benefits include reduced wear and tear on the motors and more precise levels of control.
Conduct Analysis for VFD Retrofit Applications to Ensure Energy Savings
VFDs do save energy, but VFD retrofit applications should be carefully analyzed to determine if they will result in the estimated energy savings. For example, variable-torque centrifugal pump or fan applications reduces the motor speed, generating sizable energy reductions, as energy use decreases by a cube function in relation to the reduction in motor speed. Most comfort cooling or water pumping applications are over-sized for conditions that exist most of the time – designed for the worst case. The VFD enables the system to match the load.
Existing systems that apply constant speed motors with mechanical restrictions to deliver variable flow are a good fit for VFDs. Also, is the system already limits flow by increasing pressure drop, a VFD makes sense. On the other hand, systems that need constant flow will usually require more costly mechanical rework to generate VFD savings.
VFDs offer more advantages beyond energy savings, including:
- Soft start
- Ability to ramp up and down
- Extend equipment life
- Eliminate water hammer problems
- Provide diagnostic data
- Track system performance
Now it is simpler and more cost-effective to connect a VFD to a building automation system, as now the serial or Ethernet data connection ports are included. There may be incentives available for VFDs from utility companies as well.
Crockett Facilities Services – Helping Property Mangers Reduce Energy Costs
At Crockett Facilities Services, Inc., our key focus is helping building owners, property managers, and facility professionals lower their operating expenses and energy costs through proactive HVAC maintenance. Give us a call now to set up an appointment for an HVAC system evaluation and to determine if VFD applications can help you improve energy efficiency.
For more information on how we can help you lower your HVAC equipment’s operating costs, please contact us by calling 301.262.2771, email sales@crockett-facilities.com, or submit a form for a service quote. Like us on Facebook; follow us on LinkedIn, Twitter, and Google+.
Sources:
Analyze VFDs, Facilitiesnet.com
Benefits of VFDs in HVAC Systems, Facilitiesnet.com