WHAT IS AHU,Actuator,FCU?

WHAT IS AHU?

The basic function of the AHU is take in outside air, re-condition it and supply it as fresh air to a building. All exhaust air is removed, which creates an acceptable indoor air quality. Depending on the required temperature of the re-conditioned air, the fresh air is either heated by a recovery unit or heating coil, or cooled by a cooling coil

An air handler, or air handling unit (often abbreviated to AHU), is a device used to condition and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system. Usually, an air handler is a large metal box containing a blower, heating and/or cooling elements, filter racks or chambers, sound attenuators, and dampers. Air handlers usually connect to ductwork that distributes the conditioned air through the building, and returns it to the AHU. Sometimes AHUs discharge (supply) and admit (return) air directly to and from the space served, without ductwork.

In buildings, where the hygienic requirements for air quality are lower, some of the air from the rooms can be re-circulated via a mixing chamber and this can result in significant energy savings. A mixing chamber has dampers for controlling the ratio between the return, outside and exhaust air.

The AHU is a large metal box containing separate ventilators for supply and exhaust, heating coil, cooling coil, heating/cooling recovery system, air filter racks or chambers, sound attenuators, mixing chamber, and dampers. AHUs connect to ductwork that distributes the conditioned air through the building, and returns it to the AHU.

A heat/cooling recovery exchanger is normally fitted to the AHU for energy savings and increasing capacity.An AHU designed for outdoor use, typically on roofs, is also known as a rooftop unit

What is a  Actuator Valve?

A valve actuator is a mechanical device that uses a power source to operate a valve. This power source can be electric, pneumatic (compressed air), or hydraulic (the flow of oil). There are two main types of actuators, one for each of the two main types of valves that require them. Both linear and rotary style actuators are available with the various power sources mentioned earlier: pneumatic, hydraulic, and electric. In addition to these, there are also several distinct types of manual operators.

FAN COIL UNIT

                A fan coil unit (FCU) is a device that uses a coil and a fan to heat or cool a room without connecting to ductwork. FCUs can be less expensive to install than ducted systems.High level of flexibility in terms of subdivision and rearrangement of space.

                                                                               

Poorly suited to open plan spaces, as adjacent units can operate in conflict

Chilled water valves and hot water valves in ceiling can be a maintenance problem.

              FCU systems are of average efficiency only but if well maintained and operated can produce a good level of efficiency.  They are generally not as efficient as standard alternatives such as variable volume air conditioning, chilled beams and displacement systems.

                    The age and condition of FCU systems will significantly affect running costs.  Older systems tend to have higher rates of temperature controller failure, poorly operating valves and inefficient central plant, all of which can increase costs.

                 efficiency will be improved by good management and  commissioning, especially in relation to the calibration of temperature sensors and the maintenance of valves.  A building management system (BMS) will provide a higher level of control and if well managed will help reduce running costs.

Upgrade of chiller plant.  Chillers have 15-20 year lifespan, although they generally have been superseded in terms of efficiency well before the end of their operational life.  Replacement of chillers is best undertaken in winter.

Control improvements can be implemented with the tenants in-situ

FCUs are found as a secondary HVAC system in most building types but are less common as a primary HVAC system type, except in shopping centres and smaller offices.

FCUs are typically ceiling mounted and thus do not take up floor space.  Positioning of existing FCUs may adversely affect the subdivision  of space. Units can, however, be moved and / or supplemented to accommodate different floor space configurations.

FCUs are generally considered a lower grade solution for office air-conditioning due to fan noise.  They can deliver good control when well maintained but the small zone size and high component count often leads to occupant discomfort.

FCUs are simple to operate and are relatively straightforward to maintain, but the components that require most maintenance – the temperature controllers and the valves – are in the occupied space and therefore maintenance can be intrusive.