The Benefits of a Variable Frequency Drive


Commercial HVAC systems often operate on three phase power, as a standard method of alternating current electric power generation, transmission and distribution. Most conventional building HVAC applications are designed to operate the equipment at a constant speed. That being said, building loads aren’t constant and motors have to perform at full load at any given time. The technology itself controls the speed of a motor, converting incoming AC power to DC and then back to quasi-sinusoidal AC power using an inverter switching circuit, giving the advantage of more speed control.

Variable Frequency Drive is found to be very effective in assisting with energy management for HVAC systems. The main objective of this technology is to ensure that the motor only generates enough energy to power the compressor and no more. VFD provides constant load-matching capacity which results in the elimination of over-capacity running. Recently studied, current variable frequency drive benefits goes beyond the advantage of energy savings or energy efficiency. In conventional common application, the installation of variable frequency drive saves about 35% to 50% energy used by matching system capacity to the actual load.

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Introduction to HVAC Systems

During the past week we’ve talked about challenges, improvements and development of HVAC technology. But taking a step back, what is a HVAC system? Heating, ventilation, air conditioning systems and refrigeration (or known as HVAC&R) is a technology developed to manipulate environment temperature and air quality. The applications of such technology are based on the principles of thermodynamics, fluid mechanics and heat transfer.

HVAC Intro

Commonly HVAC systems are grouped into four main systems starting with the heating and air conditioning split system, which is the most ordinary implementation of residential applications encompassing both inside and outside installations. The application, which can be controlled with a central thermostat, consists of air conditioning system which cools the refrigerant to drop the temperature, and heating system which involves gas furnaces. Ducts used to circulate the adjusted air from both heating and conditioning, with the help of evaporator/fan coils – a terminal unit which is used to provide heating or cooling to the targeted space.

A split system is known for its simplicity, efficiency and low cost.  That being said, the second type (hybrid heat split system) is actually found to benefit over the first one from an energy efficiency standpoint since the application utilizes heat pump systems. With the incorporation of heat pumps, the system is able to pump cooled or heated refrigerant to make both system able to be controlled through electric power. The heat pump is used to move energy using outside surrounding air as an air source for heating and heat sink for refrigeration/conditioning systems.

A duct free split system would benefit the most to be installed at locales where conventional ducts cannot fit or are not directly connected to central control thermostats. No ductwork would be needed in the system, thus enabling flexibility of delivering air directly to the targeted zones. Since the technology allows you to directly zone the cooled air, using ductless technology could improve efficiency, lower operation cost and reduce carbon footprints.

The last system to note is the packaged heating and air conditioning system – which is normally the system that is installed at locales where there is not enough spaces available for  the components of the split system. A package unit has a heating and cooling system combined into one unit,  making it easier to access for maintenance as well as to be conservative on installation space.


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