**Advantages of fan coil unit**s


**Figure 14.** *A schematic diagram of a fan coil unit. Readapted from [5].*

## **Disadvantages of fan coil unit**s


*2.2.2.2 Multi-piping systems*

*Central Air Conditioning: Systems and Applications DOI: http://dx.doi.org/10.5772/intechopen.89455*

three-pipe all-water-type system.

a four-pipe all-water-type system.

In these systems, there are two pipes for providing hot and cold water to the fan

*A schematic diagram of a fan coil unit, two-pipe system of direct return. Redrawn with modification from [2].*

In these systems, there are two pipes for providing hot and cold water to the fan coil unit and two pipes for return, one for cold water return and one for hot water return (four-pipe system). These systems are considered as the best system as the use of two return pipes can maintain efficient energy performance. **Figure 18** shows

In these systems both air and water produce heating and cooling effects. Usually induction or fan coil units can be used in air-water systems. The following section

will describe the induction unit systems and fan coil system [1–5].

*A schematic diagram of a fan coil unit of three-pipe system. Redrawn with modification from [2].*

coil unit and one pipe for return water (three-pipe system). **Figure 17** shows a

*A. Three-pipe systems*

**Figure 16.**

*B. Four-pipe systems*

**2.3 Air-water systems**

**Figure 17.**

**15**

### *2.2.2 Types of all water systems*

The all water systems are classified based on water pipe connections to the fan coil units, into two types [1–5], namely:

#### *2.2.2.1 Single piping systems*

#### *A. Single piping system (reversed return)*

In this system, there are two pipes, one pipe to feed either the cold or hot water to the fan coil unit and another pipe for returning the water back to the chiller or boiler (see **Figure 15**). In these systems the supplied water is in counterflow with the return water.

#### *B. Single piping system (direct return)*

In this system, there are two pipes, one pipe to feed either the cold or hot water to the fan coil unit and another pipe for returning the water back to the chiller or boiler (see **Figure 16**). In these systems the supplied water is flowing in a pipe which is connected directly to the chiller or boiler, where the same pipes receive the return water from each fan coil unit.

**Figure 15.** *A schematic diagram of a fan coil unit, two-pipe system of reversed return. Redrawn from [2].*

*Central Air Conditioning: Systems and Applications DOI: http://dx.doi.org/10.5772/intechopen.89455*

**Figure 16.** *A schematic diagram of a fan coil unit, two-pipe system of direct return. Redrawn with modification from [2].*
