This is a very basic overview of a chilled water HVAC system for people in other parts of a facility management program including purchasing, administration and even non-mechanical executives.

A commercial chilled water HVAC system is a type of air conditioning system that works by circulating cold water through plumbing and mechanical equipment to cool the air in a building. This type of system is commonly used in large buildings such as office buildings, hospitals, and schools.

Chilled Water HVAC – The Sum of its Parts
The chilled water HVAC system consists of several key components that work together to provide cooling. These components include a chiller, air handling units, pumps, piping, and evaporator coils.

The Chiller

This is the heart of the system and is responsible for cooling the water that is circulated throughout the system. The chiller works by taking in warm water from the building and using refrigeration technology to cool it down. The cold water is then pumped out of the chiller and circulated through pipes to the air handling units.

The Air Handling Units (AHU)

These are located throughout the building or on the rooftop, and are responsible for distributing the cool air throughout the occupied space. Each air handling unit contains evaporator coils that are filled with the cold water from the chiller. As warmer air from the building return ductwork, often mixed with fresh outside air, is blown across the coils the set temperature moved into the supply ductwork. The AHU coil piping absorbs the heat from the air, which causes the water to warm up. This warm water is then pumped to a cooling tower and back to the chiller to be cooled again.

The Cooling Tower

These are commonly located on the rooftop or adjacent to the building. A cooling tower uses evaporative cooling to disperse the warm temperature of the water sent to it from the AHU. The heated water is sprayed onto the large surface area of the infill, while large fan draws air through in all directions to cool the heated water as it cascades down into the basin and is returned to the chiller.

The Pump

Pumps are responsible for moving the chilled water through the piping system. The piping system is designed to distribute the water to the air handling units and back to the chiller. The pumps ensure that the water is circulated at the correct pressure and flow rate to provide optimal cooling.

Overall, the chilled water HVAC system works by using a chiller to cool water that is then circulated through air handling units to cool the air in a building. The evaporator coils within the air handling units play a critical role in cooling by transferring the temperature from the chilled coil fins into the air stream when pressurized air is moved across and through it.

AHU and Energy Efficiency
Now, when it comes to maintenance, it’s important to keep the chilled water HVAC system clean and running smoothly. If the system isn’t properly maintained, it becomes less energy-efficient over time. For example, dirty air filters restrict airflow, which makes the HVAC system work longer to cool the building. A dirty evaporator coil reduces the efficiency of the chiller, which can lead to higher energy bills. Leaks in the chilled water pipes can also waste energy and increase operating costs.

Test. Don’t guess.
It’s important to assess the conditions of the AHU and evaporator coil on a regular basis. HVAC condition assessments determine whether or not the AHU is affecting energy efficiency or even indoor air quality. As a matter of fact, ASHRAE Standard 62.1, Section 8, Ventilation and Acceptable Indoor Air Quality recommends that an operations and maintenance manual be created for the entire HVAC system. In this guidance there is a list of HVAC components to inspect and maintain, as well as at what frequency. WTI | Pure Air Control Services is ready to help your facility with these assessments or even in the creation of a preventative maintenance program.

HVAC Steam Cleaning to the Rescue
Heavy fouling across and within the evaporator coil fins causes airflow restrictions. As previously mentioned, his buildup of debris also causes the coil to be insulted preventing it to transfer the temperature as designed. Surface cleaning of the coil with detergents and low pressure spray removes some of this debris but not all of it. The best method for removing debris and throughly restoring airflow to the coil fins is HVAC steam cleaning. This process uses high temperature, medium pressure steam to sanitize and eliminate airflow obstructions from deep within the coil. WTI | Pure Air Control Services has a proprietary, 14-point process to clean AHU coils in a chilled water HVAC system.

Regular maintenance, such as steam coil cleaning, changing air filters, and checking for leaks, keeps the chilled water HVAC system running efficiently and reduce energy costs. In fact, studies have shown that properly maintained HVAC systems are 20% or more energy-efficient than poorly maintained systems. For more information on HVAC conditions assessment and steam coil cleaning please contact us today!

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