Summary of Different Air-Conditioning Systems

System

Advantages

Disadvantages

All Air

• Central equipment location

• No piping in occupied area

• Use of outside air (free cooling)

• Easy seasonal change

• Heat recovery possible

• Closest operating conditions

• Duct clearance

• Large ducts — space

• Air balancing difficulties

Air

Water

• Individual room control

• Separate secondary heating/cooling

• Less space for ducts

• Smaller HVAC central equipment

• Central filter, humidification

• Changeover if only two pipes

• Operating complex if two pipes

• Control is numerous

• Fan coil clearance problem

• No-shut off for primary air

• High pressure for induction

• Four pipe system is too expensive

All

Water

• Less space

• Locally shutoff (individual control)

• Quick pull down

• Good for existing buildings

• More maintenance in occupied area

• Coil cleaning difficulties

• Filter

• Open window for IAQ

Uni­

Tary

• Individual room control

• Simple and inexpensive

• Independent of other buildings

• Manufacturer made it ready

• Limited performance

• No humidity control (general)

• More energy (low efficiency)

• Control of air distribution

• Filter

• Overall appearance