HVAC Variable Frequency Drives

In commercial HVAC control is important to maintain good energy efficiency. Before the energy crunch of the seventies and even into the nineties almost everything ran full blast and was controlled by temperature alone and nothing else in many commercial HVAC applications. The rise of fuel and energy costs brought with it a rise innovation and the technology available for commercial HVAC applications. It became increasingly important for manufacturers to build more efficient machines to provide heating and cooling for the commercial end user. The equipment cost more but in the long run would pay for itself in a few short years in energy savings. A big innovation in energy savings was the variable frequency drive. The variable frequency drive added efficiency to systems by making it possible to speed up and slow down electric A.C. motors based on demand. The age of running an electric motor full blast all day long ended when this innovation, the variable frequency drive, was first used in commercial HVAC.

How Variable Frequency Drives Work

Variable frequency drives work by changing the frequency of the power supplied to the motor. By changing the frequency of the power the speed can be changed. Blower fans and pumps can be modulated based on demand. Variable frequency drives need a method of control to modulate the electric motor. Some variable frequency drives have a built in controller which, when programmed, will control a motor based on a set of instructions in the program. Other variable frequency drives need an external controller which will signal the variable frequency drive when to speed up and slow down. Modern systems rely on a direct digital control system and application for this function. Based on an input variable the direct digital control system will send a signal to the drive to speed it up or slow it down depending on the direct digital control programming.

Variable Frequency Drive Energy Savings

Other names for variable frequency drives are variable speed drives, AC drives, and adjustable speed drives. These systems often pay for themselves within a few years by offering energy savings through precision control of the HVAC based on actual demand for heating and air conditioning. If there is only a need to run the HVAC system at 50% then the system is programmed to run the HVAC system at 50% and the results are energy savings to the customer. Variable frequency drives or variable speed drives help save in energy costs for the consumer.

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