How a Chilling, Cooling Tower, and Air Handling Unit Work Together

When it comes to heating and cooling an office space or larger building, the use of a commercial or industrial-sized HVAC system is needed in order to properly meet the needs of the entire building. In order to have a better understanding of how the HVAC system in a larger office building works, you need to know how the chiller, cooling tower, and air handling unit work together.

A water-cooled chiller is a large piece of equipment used industrially and located in the interior of a building, containing the evaporator and the condenser. The cooling tower acts as a large heat exchanger that sits on the roof of the building. When these two items work together, it becomes possible to condition the air in large open spaces, such as industrial buildings and factories.

The minimum system components of the central cooling plant include:

  • Chiller
  • Air Handling Unit
  • Cooling Tower
  • Pumps

The location of the chiller depends on the type of chiller that is used, and rooftop ones are usually air-cooled while the basement chillers are water-cooled. Both perform the same function, which is usually to generate cold water for the air conditioning by removing the unwanted heat away from the building. The only difference is the way that the chiller discards the heat. The question that you should be asking yourself is, “How do a cooling tower and a chiller work together?” We’re going to answer that for you below and provide you with more information on how this is possible in order to give you a better understanding of it all.

Air Cooled VS Water Cooled

It’s important to know the difference between air-cooled and water-cooled chillers. Air-cooled chiller will use fans to expel the cool air over the condenser to remove the heat from the system and air-cooled chillers do not use a cooling tower.  The evaporator of the chiller generates the chilled water, which then 

cooling tower

leaves the evaporator at around 43°.

This is then pushed around the warehouse or facility by a chilled water pump, with the chilled water flowing up the height of the building to each floor in risers – the pipes which carry the water. Even when the water flows down, these pipes are still known as risers. Chilled water funnels into the risers and then into smaller diameter pipes that then follow into the fan coil units – FCU’s – and the air handling units – AHU’s – which then provide the building with air conditioning. 

Both the AHU’s and the FCU’s are boxes with fans that suck in air from the building and push it over the heating or cooling coils and change the air temperature. This air is then pushed back to the outside of the building. It should be noted that chilled water is referred to as such, even if it’s warm to touch! So, how does a cooling tower and chiller work together?


cooling towerThe chiller is typically located within the roof or basement of the office building. The chiller’s job is to produce cold water for conditioning the air by means of removing the heat from the building. The evaporator cylinder is the piece responsible for producing cold water used for air conditioning. It flows through a coil inside of the air handling unit where the indoor air blows over it, transferring the heat from the air into the water. This leaves the cooler air to distribute around the building. The chilling tower can either be cooled using water or air, but either way, the outcome is the same, which is the cooling of the air.

Cooling Tower

cooling towerWhen the heat is removed from the space by the chilling tower, the cooling tower serves to pump the air through the pipes into the cooling tower. The cooling tower then returns that heated air as cooled air through its evaporation process. The cooling tower has a float system that controls the amount of water within the system in order to prevent the total evaporation of the water. Freshwater is then introduced to the system once the float reaches the level. A valve is then opened for the fresh water to come into the system. The water is cooled and helps to produce the cool air throughout the HVAC system. The cooling tower is the final destination for the unwanted heat in the building to escape to the outside.

Air Handling Unit

The air handling unit works alongside the chilling and cooling towers in order to circulate and maintain the air through the process of heating, ventilation, and cooling or air conditioning. The air handler on a commercial unit is a large box that is composed of heating and cooling coils, a blower, racks, chambers, and other parts that help the air handler do its job. The air handler is connected to the ductwork and the air passes through from the air handling unit to the ductwork, and then back to the air handler.

All of these components work together depending on the scale and layout of the building. If the building is large, multiple chillers and cooling towers could be required, and there may be a need for a dedicated system for a server room so that the building can receive adequate air conditioning when it is required.

As you can see, the parts of the commercial HVAC system, the chilling tower, cooling tower, and air handler, all work together to produce the desired outcome for effectively cooling the building. If you have any questions or if you want to learn more about our commercial services, call us at (910) 777-3539