Building Chiller Requirements: Factoring in the Invisible Elements

Whether you’re involved in a new building or a refit, the correct design and product selection of the building chiller system is a critical one. As an essential element in any commercial or industrial space, your choice of chiller needs to take into account a host of factors to ensure longevity, energy efficiency, maximum uptime and adherence to local legislature.

From manufacturing plants to malls, high-rise office blocks to hospitals, all depend on the cleaning, cooling and dehumidification that building chiller systems deliver. However, no two buildings – indeed – no two days are the same, so our trusty chiller needs to be versatile and robust. Let’s take a closer look at building chiller requirements which deserve consideration.

Energy Costs

It’s no secret that chiller systems are hungry beasts, and according to the US Department of Energy, can account for over 50 percent of the total energy use of a building. When considering your HVAC options, initial costs versus energy efficiency should be weighed carefully.

Avoid false economy by choosing a smaller system than your building requires, as this results in an overworked chiller, higher maintenance costs and a shorter lifespan. A system which is too large is a waste of money at the outset and uses only a portion of its capacity.

Regular maintenance of your chosen chiller system is a vital key to its overall efficiency. An inefficient system can cost companies millions annually if left unchecked, and if reducing building operating costs is an important factor to you, then supporting an efficient chiller system is a good place to start to reduce energy consumption.

Building requirements in South Africa have already been laid out in terms of chiller efficiency guidelines which specifies the minimum standards of building design and building services, including environmental control.

An article from Lawrence Mechanical had this to say about building chiller systems; “Energy efficiency is a primary concern among owners & facilities managers of high-performance buildings.  In fact, ASHRAE Standard 90.1-2013 shows water-cooled centrifugal chillers with capacities of 400 ton or more to be more efficient than other mechanical cooling technology, including air-cooled chillers, rooftop units, and self-contained systems, said Christine Detz, senior product manager of centrifugal chillers, building technologies and solutions, Johnson Controls Inc.

“Water-cooled chillers can also be designed to function over a wide operating envelope, which means warmer chilled water temperatures and colder tower water can be used for greater energy savings,” said Detz. “Other types of chiller designs, such as air-cooled free-cooling chillers or variable-speed drive (VSD) chillers, can minimize compressor runtime, which helps to increase energy savings even more. In other words, chillers deliver efficiencies, capacities, and options that make them advantageous for buildings designed for exceptional performance — not just for energy savings but also for cost-effectiveness, sustainability, functionality, productivity, and other performance-related criteria.”

Tonnage Calculations

Careful calculations need to be performed in order to get the correct sized chiller system for your unique needs. Factors that influence your building chiller requirements include:

• Heat conduction from walls which includes building location, alignment, insulation and building size.
• Heat from the roof.
• Heat from windows and doors.
• Body heat generated by employees, which varies depending on passive (office) versus active (manufacturing) environments.
• Heat produced by lighting, ovens, computers and other equipment
• Outside weather conditions (Climate)

There are online sources (and rules of thumb) that are often referred to in order to get an approximate tonnage calculation in order to determine the correct size of your building’s chiller system. An example is a formula known as the “Manual J” method and can be found here.

However, as previously mentioned, getting a professional to perform the necessary measurements is the best way forward, and will guarantee you an adequate and efficient system. Future growth and changes can be factored in too.

Building Materials Can Help or Hinder

An interesting piece worth reading at Whole Building Design Guide says, in part, “Energy-efficient, climate responsive construction requires a whole building perspective that integrates architectural and engineering concerns early in the design process. For example, the evaluation of a building envelope design must consider its effect on cooling loads and daylighting. An energy-efficient building envelope, coupled with a state-of-the-art lighting system and efficient, properly-sized HVAC equipment will cost less to purchase and operate than a building whose systems are selected in isolation from each other.”

It goes on to detail various design features which can assist in the heating and cooling of a building in the most efficient way.

“The building should incorporate as many features as possible that reduce heating and cooling loads, for example:

• In skin-load dominated structures, employ passive heatingor cooling strategies (e.g., sun control and shading devices, thermal mass).
• In internal-load dominated structures, include glazing that has a high cooling index.
• Specify exterior wall constructions that avoid thermal bridging.
• Detail the exterior wall constructions with air retarder systems.
• Incorporate the highest R-value wall and roof construction that is cost-effective.
• Design efficient lighting systems.
• Use daylight dimming controls whenever possible.
• Specify efficient office equipment (e.g., EPA Energy Star® Office Equipment).
• Accept life-cycle horizons of 20 to 25 years for equipment and 50 to 75 years for walls and glazings.”

Smart Companies Create Smart Buildings

If you have the good fortune to design and build a new building from scratch, then there’s a good chance you’re considering a smart building. Smart buildings share data and tech between systems to optimise HVAC performance, reduce energy usage, ensure the smallest carbon footprint, and make the building as secure and comfortable as possible.

Modern chiller systems link seamlessly into smart buildings with an easy interface to maintain, report and manage.

What are your building chiller system requirements? AHI has been advising commercial entities for decades with regard to their HVAC systems, and have been trusted with some of the most demanding installations in the world. You can trust us with yours.

Contact us today.