Make the most of variable frequency drives

3 min read

Wondering whether VFDs are a good fit for your business? Learn more about how they can deliver maximum savings.

How VFDs work

When some manufacturing machinery is first powered on, it starts with a jerk as it goes immediately from “off” to full power. A VFD ensures a smoother start that is easier on your equipment. With a VFD, you can also power only as many stations as are being used at a certain time; for example, if only three out of 10 work stations happen to be in operation, the motor will run at 30% power instead of 100%. By adjusting voltage and frequency, VFDs help motors operate at the most efficient speed for any given use. Once they are installed, they work automatically—you don’t have to think about them.

Three advantages to VFDs
  1. Save energy: VFDs help your business run more efficiently by using only as much energy as needed.
  2. Save money: When you save energy, you save money. A VFD usually pays for itself within two years thanks to lower energy costs, and this payback period can be significantly shortened (to as little as three months) when you take advantage of available rebates on high-performance equipment.
  3. Save your equipment: VFDs extend the lifetime of your equipment by decreasing wear and tear. Maintenance costs are also reduced.
Good uses for VFDs
  • Fans, such as cooling tower fans, exhaust fans, air supply fans, boiler draft fans, kitchen hoods, HVAC rooftop units, and dust collection fans
  • Pumps, such as hot water pumps, chilled water pumps, process pumps, and water source heat pump loops
Businesses can realize notable savings from using VFDs

Fans and pumps that are turned down just 10% can save up to 25% in energy costs. In most systems, reducing its speed by 50% can cause a 75% drop in energy consumption. A rooftop controller for a 10-ton HVAC system saves $610 per year on average. (Savings from a 3 hp 10 ton rooftop unit supply fan are 6,100 kWh—$610 per year at $.10/kWh.)

Installation of variable frequency drives is a specialized skill

Proper installation is vital to VFD performance. Installation must take into account the location, environment, humidity levels, grounding, supply voltage, motor protection, and other factors. Even for experienced do-it-yourselfers, we strongly recommend hiring a professional installer. The installer will know exactly how to set up your VFDs to maximize the efficiency of your individual equipment setup.

An easy fix: rooftop controllers

HVAC systems present an almost “plug-and-play” option for using a VFD. Unlike the specialized equipment used in industrial processes (for which each motor needs its own equally specialized VFD installation), HVAC rooftop units are common and relatively standard. Because they are designed to work on the hottest and coldest days of the year, HVAC units also tend to be highly inefficient—and thus can benefit greatly from an upgrade. A “rooftop controller” is a simplified VFD paired with a controller unit. Adding one to an HVAC system is an easy fix to make, and can deliver big energy savings.