AHU vs FCU

AHU vs FCU AHU vs FCU

AHU and FCU are both included in the HVAC system. The latter is an acronym that describes multiple systems of  heating, ventilating and air conditioning. AHU, completely known as air handling unit is different from FCU or the fan coil unit. AHUs are usually connected to a central HVAC system whereas an FCU can function or be installed itself. Because of this, it is often the AHU that is used to ventilate an entire building whereas FCUs are used in smaller and often local spaces only. It is no surprise that AHU is the bigger HVAC system not to mention, the FCU is also regarded as the smaller version of the AHU. In this regard, the smaller FCUs can be called terminal units. Because of the magnitude of the AHU system, it usually makes use of the air from the outside environment. Thus, it treats outside air and brings it inside the vicinity with the use of special ducts while an FCU system on the contrary just circulates the inside air. The latter usually does not have any duct system thats why it is obviously smaller in size as previously mentioned. It is only composed of a simple coil and fan. Ordinarily, AHUs have certain features that are not present in the FCU type. AHUs have several sections for reheating and even humidifying. FCUs dont have sections such as these. Perhaps the only advantage that the FCU has over the AHU is that generally, FCUs can also handle water while the AHUs basically handle air. Moreover, AHUs can have several fans or blowers installed in its system. Traditionally, the AHUs blowers are placed at the point where the ducts originate or at the terminal end of the air handler unit. FCUs have a different approach to blowers. Because of its small size, their fans are usually placed within the same space as the unit itself. The result is a minor uncomfortable noise that can be heard within the vicinity. This could be regarded as the single most advantageous flaw of the FCU system. Summary: 1. AHU is generally a bigger system than FCU. 2. AHU is more complex than the FCU and that AHU are often used in bigger establishments or spaces. 3. The AHU system usually channels air through ducts whereas the FCU dont have any ductworks. 4. AHU system treats outside air while FCUs basically recycle or re-circulates the air. 5. AHU have sections for reheating and humidifying whereas the FCU does not have any. 6. FCU are often observed to be noisier than the AHU. Read more: Difference Between AHU and FCU | Difference Between http://www.differencebetween.net/obj http://www.differen cebetween.net/object/difference-be ect/difference-between-ahu-and-f tween-ahu-and-fcu/#ixzz0zWxUQ cu/#ixzz0zWxUQ5me 5me

What is the diff erent between Air handling unit(AHU) and Fan coil unit(FCU)?.and How does AHU and FCU work? AHU is a generic term for anything that moves and heats/cools air. The discharge is generally directed to air ducts. This would include rooftop units, makeup air units, furnaces, etc. A fan coil unit is usually a l ot smaller and self contained. The internal fan passes air over a heated/cooled coil and immediatly discharges it to the surounding air. There is no ducting involved. FAN COIL UNIT(FCU)

A f an coil unit (FCU) is a simple device consisting of a heating or cooling coil and fan. It is part of an HVAC system found in residential, commercial, and industrial buildings. Typically a fan coil unit is not connected to ductwork, and is used to control the temperature in the space where it is installed, or serve multiple spaces. It is controlled either by a manual on/off switch or by thermostat. Due to their simplicity, fan coil units are more economic to install than ducted or central heating systems with air handling units. However, they can be noisy because the fan is within the same space. Unit configurations are numerous including horizontal (ceiling mounted) or vertical (floor mounted). A fan coil unit may be concealed or exposed within the room or area that it serves. An exposed fan coil unit may be wall mounted, freestanding or ceiling mounted, and will typically include an appropriate enclosure to protect and conceal the fan coil unit itself, with return air grille and supply air diffuser set into that enclosure to distribute the air. A concealed fan coil unit will typically be installed within an accessible ceiling void or services zone. The return air grille and supply air diffuser, typically set flush into the ceiling, will be ducted to and from the fan coil unit and thus allows a great degree of flexibility for locating the grilles to suit the ceiling layout and/or the partition layout within a space. It is quite common for the return air not to be ducted and to use the ceiling void as a return air plenum. The coil receives hot or cold water from a central plant, and removes heat from or adds heat to the air through heat transfer. Traditionally fan coil units can contain their own internal thermostat, or can be wired to operate with a remote thermostat. However, and as is common in most modern buildings with a Building Energy Management System (BEMS), the control of the fan coil unit will be by a local digital controller or outstation (along with associated room temperature sensor and control valve actuators) linked to the BEMS via a communication network, and therefore adjustable and controllable from a central point, such as a supervisors head end computer. Fan coil units circulate hot or cold water through a coil in order to condition a space. The unit gets its hot or cold water from a central plant, or mechanical room containing equipment for removing heat from the central building's closed-loop. The equipment used can consist of machines used to remove heat such as a chiller or a cooling tower and equipment for adding heat to the building's water such as a boiler or a commercial water heater. Fan coil units are divided into two types: Two-pipe fan coil units or four-pipe fan coil units. Two-pipe fan coil units have one (1) supply and one (1) return pipe. The supply pipe supplies either cold or hot water to the unit depending on the time of year. Four-pipe fan coil units have two (2) supply pipes and two (2) return pipes. This allows either hot or cold water to enter the unit at any given time. Since it is often necessary to heat and cool different areas of a building at the same time, due to differences in internal heat loss or heat gains, the four-pipe fan coil unit is most commonly used.

Fan coil units may be connected to piping networks using various topology designs, such as "direct return", "reverse return", or "series decoupled". See ASHRAE Handbook "2008 Systems & Equipment", Chapter 12. AIR HANDLING UNIT(AHU)

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. An air handler is usually a large metal box containing a blower, heating 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. Small air handlers, for local use, are called terminal units, and may only include an air filter, coil, and blower; these simple terminal units are called blower coils or fan coil units. A larger air handler that conditions 100% outside air, and no recirculated air, is known as a makeup air unit (MAU). An air handler designed for outdoor use, typically on roofs, is known as a packaged unit (PU) or roof top unit (RTU). Description Size Installation Method Cost Blowing Capacity

Application

Air Handling Unit Big size compared to FCU Mounted on floor, usually a room (AHU ROOM) is required to be provided More expensive In term of capacity (CFM) The AHU can supply much bigger CFM compared to FCU. The blower for the AHU allows you to design at higher static head and CFM -Used for the area where the ceiling space is very limited

Fan oil Unit Smaller size Mounted at the ceiling level, not requiring a room Cheaper compared to AHU The CFM of the FCU is less than AHU. However, it creates less noise compare to AHU. - For the building where building space is limited

-For building where there is a lot of rooms and most of the time those room will be occupied (i.e office building)

- For building where not all the time that room will be used by the user. Different rooms have different operating hours (i.e. laboratory or research facilities)

-In terms of maintenance consideration, AHU will have less maintenance work especially for those large building as the number required is less.

-More maintenance work, as the units of FCU required for the same space is higher compare to AHU

-Less flexibilities in term of energy saver (power consumption) as it has to run in full load each time you start it, even though some of the room might not be occupied by the user.

- Have more flexibility in terms of  energy consumption as separate room has its own FCU that can be switched off if not in use.