HVAC SYSTEM

HVAC SYSTEM

Air conditioning systems type

1- Direct Expansion (DX)

2- Indirect Expansion (chiller)

Direct expansion the air is cooled by freon while (chiller) the water is cooled by freon then the air is cooled by water . 

Direct expansion type 

• Package units ( window, central package) and central package divided to (roof top , vertical)
• Split units (central split , mini split) and the mini split divided to (High wall , floor and ceiling , cassette, ceiling concealed duct , vrf ) 

chiller 

• Water cooled chiller.
• Air cooled chiller.
• Absorption chiller

HINT: 
Indoor unit from chiller Fan Coil Unit ( FCU ) & Air handing unit (AHU)

Comparison between (DX) and ( chiller)

(DX)

• Low initial cost
• High running cost
• Easy for maintenance 

Chiller

• High initial cost 
• Low running cost
• Complicated maintenance

Window

Window

• All cooling components are in one piece.
• The cheapest type in air conditioning devices .
• His voice is high .
• It needs to be opened in a large wall.

Central package unit .

Central package unit.

• It consists of one large piece . Includes all parts of the cooling cycle.
• It must be placed in an open place for air, because heat out her when operating .
• Its voice is high .
• Cold air this type shall be transported by means of ducts and air outlets within the place to be conditioning . 
• the return air is pulled by ducts.
• The unit has a mix box where fresh air is mixed with the air returning from the place .
• A sound dampening is installed at the output of the unit to absorb the sound resulting from the unit .
• The cooling capacity of this type is large . up to 50 ton of cooling and more.

High Wall type

High wall 

• Its about two separate unit .

• The internal unit ( is installed inside the place) . it consists of evaporator and its fan.

• The Outdoor unit ( is installed out side the place ) . it consists of condenser and expansion valve and compressor and fan .

• The internal unit and outdoor unit is connected them by copper pipe.

• His voice is low due to the distance of the out door unit from the place to be conditioning .
• The internal unit does not need a large opening .
• Its cooling capacity is bigger than the window up 36000 BTU/hr .

Ceiling -floor type

ceiling - floor type .

 Its a unit composed of two separate units.

• Outdoor unit 
• indoor unit
• The outdoor unit and indoor unit connected them by copper pipe.

• The internal unit is installed on the wall above ground . or on the ceiling.
• Its preferable to install this type on the roof .because the air outside the unit is cold and its density is high and its down. the hot air in the place to be up .
• The disadvantages of this type that occupies space when installed on the ground and is not installed on the a fall ceiling .
• Its cooling capacity is greater than High wall up to 40000 BTU / hr
• When installed on the ground leaves a distance above the ground 20 cm . this is because the return air drag is down .

Cassette

Its unit composed two separate units :

• Outdoor unit .
• Indoor unit .
• The outdoor unit and indoor unit connected by copper pipe .

• This type is better in the distribution of air than the previous types. because the air comes out in the form round flow of the four directions .
• This type is installed in places that have fall ceiling just .
• cooling capacity up to 4 T.R  .
• The internal unit contains the pump . in order to pump drain water to the nearest drainage point .

Free stand

• This conditioning is named ( free stand ) and its scientific name is ( floor stand )
• Its carrying capacity is 5 T.R and possible up to 6 T.R  .
• This type is characterized by a strong fan and the height of this air conditioning to the height of human height . its used in places where there are large human clusters and high ceilings .

Concealed 

Its unit composed two separate units :

• Indoor unit ( concealed ) .
• out door unit .

• The internal unit is installed under the falling ceiling.
• Cold air is transferred throw ducts and air outlets( grill and diffuser).
• Sometimes we do not need to ducts.
• Its preferable to install this unit in service areas such as bathrooms or kitchens or crodior area.
• Give high cooling capacity .

Air ducts are not always used with this type 

• If no air ducts are used , the unit is selected according to the cooling load .
• If the air duct is used . the static pressure is calculated . it expresses the resistance that the internal fan will face. therefor , st.p first must be calculated and the appropriate unite is selected according to the required cooling capacity and st.p  .

Central air conditioning :

• Outdoor Unit

AIR Cooled Chiller

Water cooled chiller

Absorption chiller

• Indoor Unit

FCU (FAN COIL UNIT )

AIR Handing Unit

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