Direct Expansion (DX) and Chilled Water type system

There are 2 types of Central air conditioning systems: 

1.  Direct Expansion (DX) type of central air condition plants 

2.  Chilled Water type of the central air conditioning plants.

In the DX system the air used for cooling the room or space is directly passed over the cooling coil of the refrigeration plant and this in turn is a major difference among the two .

In case of the chilled water system the refrigeration system is used to first chill the water, which is then used to chill the air used for cooling the rooms or spaces.

A direct expansion air conditioning (DX) system uses a refrigerant vapor expansion/compression (RVEC) cycle to directly cool the supply air to an occupied space. Expansion refers to the treatment of the refrigerant (a valve reduces its pressure and temperature) prior to it entering the evaporator.


What does DX mean in HVAC terms..

A direct expansion air conditioning unit, also called a DX unit, cools indoor air using a condensed refrigerant liquid. It is the type of air conditioning unit most commonly used in homes.

What is a DX unit..

DX systems (both packaged and split) directly cools the air supplied to the building because the evaporator is in direct contact with the supply air, Expansion refers to the treatment of the refrigerant (a valve reduces its pressure and temperature) prior to it entering the evaporator.


What is a DX Chiller.

DX Units vs. Chillers. The immediate and most noteworthy difference between these two units is that the DX (direct expansion) unit cools air, and chiller units cool water. DX Units vary in use between supplemental or emergency building AC, or primary AC at tented events or relief structures.

What is DX coil in AHU.

Direct Expansion (DX) Type of Central Air Conditioning Plant. In the direct expansion or DX types of air central conditioning plants the air used for cooling space is directly chilled by the refrigerant in the cooling coil of the air handling unit

What is a split DX system.

A split system is a combination of an indoor air handling unit and an outdoor condensing unit. The indoor air handling unit contains a supply air fan and an air-to-refrigerant heat exchanger (or cooling coil), and the expansion device. The outdoor condensing unit consists of a compressor and a condenser coil.