Hello friends, I am Tanweer Ahmed Today will explain DX-FAHU Its mean is that Direct expansion fresh air handling unit What is DX-FAHU? and which are the main parts? and why is installed? and where is it required? These points will be explained practically through video and also explain each part through drawing therefore suggested watching video and get knowledge DX-FAHU Friends for understanding DX-FAHU then should 1st understand the single split AC As single split AC units are installed in our houses they have main two parts one is indoor unit and another is outdoor unit and we say single split AC DX-Coil unit. Cooled evaporator circulate the air through the blower in the room and room temperature reduced or down gradually through evaporator and required set temperature maintain through this way This same single split AC unit is used in DX-FAHU and evaporator coil is installed inside the FAHU unit and copper tubes and its power wires are laid in tray for outdoor unit and connected with outdoor unit You suppose indoor AC unit is installed inside FAHU unit and out door unit is connected like same This DX-FAHU unit has inside single split AC unit Suppose for understanding point of view Indoor coil is installed inside FAHU therefore we say DX-FAHU If this single split type evaporator and condenser unit are not installed in any FAHU unit then we say simple FAHU i.e.
Fresh Air Handling Unit without DX coil If evaporator and condenser are installed then we will say DX-FAHU unit and here you can see This is a condenser unit and here evaporator coil is installed inside FAHU This is condenser coil and this is an evaporator coil the evaporator coil is installed inside FAHU unit This is a condenser unit which has installed condenser coil and compressors are installed inside it condenser and evaporator are connected with each other with refrigerant copper tubes This is pre-treated FAHU unit to whom we say DX-FAHU unit DX-FAHU saying because like single split AC unit condenser and evaporator are installed This FAHU unit has 100% fresh air which cross the evaporator coil which to be cool or warm if your DX-FAHU unit is a reversible type then in winter fresh air to be pre-treat as hot and supply to condition space In summer, we pre-treat the atmosphere fresh air through this coil and make the air cool by crossing this coil air suction from coil left side and supply the fan is installed inside the unit and other parts will explain to you one by one but this unit intake or suction the 100% fresh air and air crossing the evaporator coil and then building supply air shall be pre-treated fresh air Pre-treated means that atmosphere air can be cool and warm through DX-coil Like our house's ACs are the reversible type and only cooling mode ACs If cooling mode ACs are installed then those units make cool air and supply cool air If reversible ACs are installed then in winter, we make the air hot If these units are reversible DX-coil is installed or heat pump is installed in winter, the evaporator coil will reverse and work as a condenser and dissipated heat of condenser will heat up supply atmosphere fresh air or pre-treated air to supply warm in winter season Suction side of FAHU We receive atmospheric air with the help of centrifugal fan inside the FAHU are four portions 100% suction air will supply with pre-treated DX-coil and 100% pre-treated air will supply in the building In starting there is a louver or called sand trap louver This has four portions 1st portion is called the mixing box and also called module or box or section However, this 1st is called mixing box and 2nd section is called the filter box and 3rd section is the DX-coil box and 4rth section is called the fan box after that, the front side supply air duct will connect, and the air supply in the building with the help of supply air duct Return air (Air Intake) will take atmosphere air always There will be no mixed air, it will be 100% fresh air and this will supply in the building and at this discharge location, the duct will connect and this duct goes into the building where fresh air is required in building or someone else location in this way duct connected then 100% pre-treated fresh air supply to the building This casing of the unit is PU insulated casing If air is pre-treated The unit inside air and atmosphere air temperature has the difference Therefore, don't want to lose energy so insulation is fixed in the casing is PU insulation and coating is powder coating casing and we say casing to this entire body and its panels are the design of thermal bridge factor and it is installed fan which is called Double Width and Double Inlet (DWDI) DWDI is called because this suction air enter both left and right side and also width is double and its static pressure is high Its corners are nylon material which protect from damages Its modules are in units or sections or pieces because these units can be easy for shifting in modules or sections from placed and it each box, like a fan box, filter box, fan box, etc.
Comes in parts and where required to install can be installed assembling easily Now will explain FAHU internal parts Suction side FAHU has Louver which is called sand trap louver because called sand trap louver Atmosphere fresh air suck with the help of a fan suction source and suction air is with dust, sand, debris, or garbage particles resist with it as those can not enter into FAHU unit However, the suction side is louver and inside with louver is VCD This 1st box is called mixing box and its outside is louver which is not connected with any duct and take 100% atmosphere air which enter through the louver installed outside and inside VCD is fixed VCD stands for Volume Control Damper or motorized damper Its function is that whatever fresh air intake and want to regulate which can be with the help of VCD This VCD work like a Valve as valves fitted with water pipelines for open or close it If the valve open less then water flow short and open full then water flow more and this VCD work like a valve These VCDs may be manual or motorized Manual VCD means, you hand open-close with hand or adjust and lock it and another is motorized it will operate automatically as per supply air demand and in these, both conditions, VCDs are installed and other cases can be used if motorized damper interlink with fire mode in case of fire then the damper will be closed automatically even, in this case, motorized dampers are used However, the initial mixing box does not have any air mixing Mostly mix the air in AHUs because their return and fresh air mixes therefore mixing box is called in AHU but here in FAHU, no air is mixing, just fresh atmosphere air intake Here is just the name mixing box but working like name Its suction (air intake) can be taken from the back or top or side It can be decided as per site condition and fabrication work of unit will be accordingly and start manufacturing as per site demand because where this unit wants to install For example, the unit side has a wall therefore side intake connection can not be taken then you will decide top side intake connection and if the topside roof has no space and the unit side has space then will decide accordingly as per site requirement intake (suction) location will be decided After mixing the box, we come to the next section which is called filter section/box this section has filters one is aluminum filters and another is the bag filters Aluminum filters are called pre-filters because the initial air intake through this filter and will filter the air of dust particles and next is bags filters in this filter box because these bag filters clean more air For example, you take a tea strainer and one strainer holes are the larger size and another small size and more small holes sizes Also HEPA filters are also used in Hospitals or Laboratories where more purified air is required This second section is for filter box here aluminum and bag filters are fixed or may be HEPA filters fix, these are required as per design or site conditions and 3rd section is DX-coil unit This is called evaporator and connected with copper tubes through condenser This is called DX-coil box because evaporator is installed inside it and under it, condensation tray is fixed for condensation water then this water goes in drain pipes As Indoor Split AC has condensation drain of evaporator and drain pipe is connected with main drain