Components Of Air Conditioning System Engage In Energy Saving Process

 

This article explain the Components Of Air Conditioning System Engage In Energy Saving Process.

 Variable Speed Drive or Variable Frequency Drive (VSD/VFD)

A Variable Frequency Drive is like the throttle on a car, it adjusts the speed of an HVAC fan or pump motor, based on demand, to save energy and prolong motor and mechanical component life. Without a VFD, an HVAC fan or pump motor is either 100% ‘on’ or 100% ‘off’. A VFD eliminates the initial power surge and mechanical shock of switching the motor from ‘off’ to 100% ‘on’. A VFD conserves energy when an HVAC control systems senses that a fan or pump motor can meet heating or cooling needs by running at less than 100% power.

 

It changes the speed of an AC HVAC fan or pump motor by adjusting or varying the frequency and voltage. For comparison, a DC motor speed is adjusted by only varying voltage. Typical frequency adjustment range in HVAC applications is from 10 - 60Hz AC. A VFD is wired in series between main power and motor. A Bypass is added to “Bypass” the VFD and run on main line power so HVAC operation is not interrupted if the VFD needs servicing

  A VFD, AC inverter, or electronic speed controller for AC motors converts the AC supply to DC using a rectifier (diode), and then converts it back to a variable frequency by using an inverter bridge.

                                                       variable frequency drive               

   

Air handlers

Most air handlers mix return and outside air so less temperature change is needed. This can save money by using less chilled or heated water (not all AHUs use chilled/hot water circuits). Some external air is needed to keep the building's air healthy.

 

Analog or digital temperature sensors may be placed in the space or room, the return and supply air ducts, and sometimes the external air. Actuators are placed on the hot and chilled water valves, the outside air and return air dampers. The supply fan (and return if applicable) is started and stopped based on either time of day, temperatures, building pressures or a combination.

 

Variable volume air-handling units (VAV)

VAVs supply pressurized air to VAV boxes, usually one box per room or area. A VAV air handler can change the pressure to the VAV boxes by changing the speed of a fan or blower with a variable frequency drive or (less efficiently) by moving inlet guide vanes to a fixed-speed fan. The amount of air is determined by the needs of the spaces served by the VAV boxes.

 

Each VAV boxes supply air to a small space like an office. Each box has a damper that is opened or closed based on how much heating or cooling is required in its space. The more boxes are open, the more air is required, and a greater amount of air is supplied by the VAV air-handling unit.

Some VAV boxes also have hot water valves and an internal heat exchanger. The valves for hot and cold water are opened or closed based on the heat demand for the spaces it is supplying. These heated VAV boxes are sometimes used on the perimeter only and the interior zones are cooling only. A minimum and maximum CFM must be set on VAV boxes to assure adequate ventilation and proper air balance.

 

Pressure sensor

A pressure sensor measures pressure, typically of gases or liquids. Pressure is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor usually acts as a transducer; it generates a signal as a function of the pressure imposed. For the purposes of this article, such a signal is electrical.

 

Pressure sensors are used for control and monitoring in thousands of everyday applications. Pressure sensors can also be used to indirectly measure other variables such as fluid/gas flow, speed, water level, and altitude.

                                                           Digital air pressure sensor 

                                                         

                                           Compact digital barometric pressure sensor

Flow sensing

This is the use of pressure sensors in conjunction with the venturi effect to measure flow. Differential pressure is measured between two segments of a venturi tube that have a different aperture. The pressure difference between the two segments is directly proportional to the flow rate through the venturi tube. A low pressure sensor is almost always required as the pressure difference is relatively small.

Differential pressure sensor

This sensor measures the difference between two or more pressures introduced as inputs to the sensing unit, for example, measuring the pressure drop across an oil filter. Differential pressure is also used to measure flow or level in pressurized vessels.

Contact Sensor

Contact temperature sensors measure their own temperature. One infers the temperature of the object to which the sensor is in contact by assuming or knowing that the two are in thermal equilibrium, that is, there is no heat flow between them.

Many potential measurement error sources exist, as you can appreciate, especially from too many unverified assumptions. Temperatures of surfaces are especially tricky to measure by contact means and very difficult if the surface is moving. It is wise to be very careful when using such sensors on new applications.

 Components Of Air Conditioning System, Variable Speed Drive, Air handler, Variable volume air-handling unit, Pressure sensor, Differential pressure sensor, Contact Sensor