How Does VSD Work In Building HVAC System?

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What is VSD in HVAC System?

VSD- a Variable Speed Drive in HVAC (Heating, Ventilating and Air-Conditioning) system is an important device that controls the electric motor speed. The variable speed drive (VSD) or variable frequency drive (VFD) also known as adjustable frequency drive (AFD), micro-drive, AC drive, inverter drive etc.

VSD attends to confirm the motor run at required specific speed as well as operates the motor at energyefficient way. The motor in heating, ventilating and air-conditioning (HACV) system massively used for regulated flow of water and air system where energy may save controlling motor speed rather constant speed.

How VSD Ensure the Motor Fault Protection?

Modern SSVSD or solid state variable speed drives have motor fault protection features and to ensure that VSD can monitors many parameters such as motor over current, motor voltage, back EMF, frequency, phase monitoring, external control faults, and motor winding problems and many other variables. In a conventional motor starter cannot monitor such items.

How Does VSD Save Energy?

Using a variable speed drive to control the motor speed anyone can improve the energy efficiency of pump or fan load. The VSD actually adjusts the rotational speed of the pump or fan-motor to achieve the required flow and flow-head. So, we can add a VSD to a pump system to change or reduce its speed to meet the requirements. Sing a VSD in motor or pump set is the best way to increase energy efficiency what will reduce the costs.

Conventional system in heating, ventilation and air-conditioning the flow of air or liquid is controlled by mechanical throttling or using valve and diverting way that is not energy efficient. But in modern HVAC system, the VSD response to a signal and control the motor speed as required means- demand is low therefore motor speed is reduced and a savings is realized in energy use which is more energy efficient. Approximately 35 to 50 percent energy is saved over conventional constant speed applications.

The Main Feature Using a VSD in Building HVAC.

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There are three main feature that work together to improve HVAC operating efficiency using VSD.

1.     VSD can ensure to operate the system at less than full load. Most of the system no need to operate at full load in maximum time of the day or day of the year. Building systems are sized for peak load conditions, generally peak load conditions occur between 1 and 5 percent of the annual operating hours. Means VSD can operate in energy saving mode around 95 percent for building HVAC system;

2.     VSD can play a vital role to oversized system designs. Considering the peak load and most operating hours. The system may design how to allow for underestimated and unexpected loads as well as future loads that might changes in usable space in the building;

3.     Most of HVAC system motors are used as induction motor which energy consumption cubical related to its speed. Means, if speed can control 25 percent then energy will be controlled around 60 percent.

What is The VSD Using Benefits in Building HVAC System?

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The most major benefit of using a VSD in HVAC system is energy savings.

Another significant benefit of the unit’s motors is starting current. When an induction motor is started, it draws a much higher current than during normal operation. This over taken current can be three to ten times the motor full-load operating current. The VSD can easily turn it as energy efficient way.

When a VSD is used, the motor can start and stop gradually rampped speed taking a limited current that definitely extend the motor life.

Most of high-rise buildings are use a booster pump system on the domestic water supply to maintain adequate water pressure at all levels through the whole building. Conventional pump controls have some limited range to operate, but VSD controlled motor can run more precise control over a wider range.