Phillips Smith Conwell



PSC Masterclass Series: Understanding Air Conditioning

Air conditioning in a large institutional or corporate building is a complex system of ventilation and ductwork often with the requirement of a specialist consultant.  In this masterclass, Director Louise Cutler talks us through how to effectively integrate an air conditioning system into any design, ways to avoid common errors and mitigate potential issues.


Let’s look at the basics.

There are a number of types of air conditioning units all suited to different locations, yet each operate with the same three principles:

1. Cooling coils to remove heat and humidity from the air using a refrigerant or cold water, with a fan circulating the air within the evaporator

2. A condenser utilising hot coils which releases the collected heat into the outside air

3. A compressor pumps the refrigerant between the evaporator and condenser to chill the indoor air


With these three principles in mind, we take a look at essential considerations in the process of selecting and documenting the appropriate system for your project:

Have you considered drainage options for large-scale air conditioning systems?

When warm air runs over the cooling coil, condensation forms like on the outside of a glass of cold liquid. With a myriad of services within a plant room, it is important to keep the drainage for large-scale air conditioning systems contained. The condensation drain needs to be connected to a conduit, and these considerations should be explored alongside a hydraulics engineer.


What are the benefits of ducted vs individual unit air conditioning?

Ducted systems operate with the same principles as wall units, just on a larger scale. Ducted air conditioning begins in large chiller units which contain the refrigerant and operate as the air cooler. This is then pushed into air handling units which have large fans to dispurse the cold air into ductwork and through vents in each room.  For fire safety standards, there must be different air handling units for the isolated fire zones to control air pressure in the instance of a fire.

Individual bulkhead units however, operate individual fan units attached to one chiller. There are two benefits to individual bulkhead units, the first being less ductwork is required freeing up ceiling space. The second is the ability to control the temperature in individual spaces. While not always necessary in corporate sectors, it is beneficial when considering where temperature can affect the nature of work being performed, such as hospital rooms and hotels.


How can you document your ceiling space effectively?

Ceiling space can influence the type of system to be specified. Ducted systems do not have allowances for the insulation surrounding the ductwork posing an issue for the construction phase. In addition, galvanised hangers are required to support the weight of the ductwork, and these hangers need to provide access panels for maintenance. One way to avoid headaches when the project is at construction phase, is to colour code the documentation, specifying the exact ductwork information, cable trays, access points and any additional information.


Are there other consultants who can provide their expert opinion?

It is imperative with large scale buildings to have consultants on board who can assess the viability of the air conditioning system with regards to their speciality. For example, an acoustics consultant will ascertain the level of noise travel occurring as a result of the air conditioning system, maintaining building efficiency and privacy between rooms; an electrical engineer will ensure the electrical system can provide the power required to run chiller units and other equipment required; a fire safety engineer should be engaged to test the zones established within the building and sign off on the air pressure control available in the instance of a fire.


Whilst a vital comfort aspect for our building users, air conditioning is often an underappreciated complexity within the design process.  Ventilation, electrical access, ceiling space and fire safety are some important considerations, however, for more detailed information regarding regulations and standards, please refer to AS1668.1-2015 and AS2913-2000 or contact us for further information.