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Hello everyone i am fresh mechanical engineer and obviously as fresh engineer i have less experience in field and obviously my questions will also be strange ,anyway i am very much interested to persuade my career towards HVAC ..so my question AHU and FCU units are classified in central system or local system? or they can be install in both system? further more if they belong to central system so which sub system to they belong all air system or all water system or all air water system?
i will be pleased if any one can answer my questions and Please do correct if am wrong and clear my confusion and concepts
Thanks to all!
Dear Zeeshan
First of all you should know what is central system and what is local system what is water based and what is DX type.
In central system the cooling is controlled by a central plant or pump room where we have pumping arrangements along with chiller which itself can be water or air cooled. This is water based system which is know as chilled water system.
Local system itself is not a common name but used when we have single unit. It can be a DX Type split\\multi split units, AHUs, Packaged units or VRV Systems where we have refrigerant for cooling only.
Therefore AHUs or FCUs can be installed in both systems
1. central (where we have both water and air systems) and
2. local system where we have only air circulation with one unit only.
Hope this is clear.
AHU is only used in Central Systems, Fcu is mainly used for central air conditioning purposes however it can be used for normal domestic use by making a proper refrigerant pipe connection to the condensing unit
air processing system can be instilled at home or any where
Definitely, AHU, used in central system and the fan coil unit(FCU) it used in the all windows against soler sun to reduce heat gain from radiation and convection soler.
It totally depends upon the type of source/plant employed for cooling or heating. FCU & AHU serving spaces through a DX (local source) are special cases; whereas FCU & AHU serving spaces through a chiller plant (central source) are general case to see in most of the project. They are usually classified as air-side system; in both the cases. The designer shall specify clearly for these equipments with their cooling/heating source at the very initial stage. The major difference is the system efficiency; FCU & AHU using DX source are less efficient compared to the ones using chilled water source (having modulating valves & using primary-secondary pumping scheme).
-The most usage of AHU, FCU in central system, chilled water (air water system)
-AHU, FCU as a names can be applied for DX units so we can use AHU, FCU for local systems according to architectural, load calculation, and designer recommendations
