Water Piping: Heating, ventilation, and air conditioning (HVAC)

WATER PIPING

Heating, ventilation, and air conditioning (HVAC) is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality.

In HVAC technology, water piping is one of the important component which regulates the temperature. Generally there are two types.

 (i) 2-pipe HVAC system

(ii) 4-pipe HVAC system

2-pipe HVAC system

A 2-pipe HVAC system is one that uses the same piping alternately for hot water heating and chilled water cooling.

4-pipe HVAC system

A  4-pipe systems have separate heating and cooling fan coil units and separate pipes for heating and cooling. This means that hot or chilled water is always available. So the system can immediately change over from heating to cooling mode.

(i) 2-pipe HVAC system

The 2 pipe system consists of a single water coil connected to two pipes (supply and return). This type of fan coil cannot cool and heat at the same time and is dependent of the actual mode of the building. (Fig. 2.15)

The 2 pipe fan coil requires a changeover sensor, to determine the mode of the system.

These units can be equipped with an auxilliary electric heater to compensate the limitations of the system.

(ii) 4 - pipe HVAC system

The 4 pipe system consists of two separate cooling and heating water coils. Each coil has its own set of pipes (supply and return) and valve. This type of fan coil cool and heat at the same time and is not dependant of the actual mode of the building. (Fig. 2.16)

Compared to the 2 pipe system, the 4 pipe fan coil does not require a changeover sensor since both hot and chill water is available.

These units can be equipped d with an auxiliary electric heater to boost the heating capacity (if required).

The 4 pipe fan coil can also use a chill water coil and an electric or gas heater. As long as the cooling and heating are independent t of each other, the system will be a 4 pipe lo sam odt ddiw batsiooaas ai tser thotel olidw ser configuration.

Advantages of 4- Pipe HVAC        

1. Four-pipe systems have separate heating and cooling fan coil units and separate pipes for heating and cooling. 

2. The system can immediately change over from heating to cooling mode.

3. Less time consuming to switch over.

4. Four-pipe systems can cool some rooms while heating others.

Disadvantages of 4- Pipe HVAC

They are more expensive to install and maintain.

They are congestion due to the increased piping.