HVAC School - For Techs, By Techs
HVAC Systems for Architects: Making Sense of the Alphabet Soup - Short #273
· Summarized
Key takeaways
- HVAC systems can be categorized into three main types: air-to-air, water-source, and air-water hybrid.
- Understanding distinctions between system types, such as DX vs. water source, is essential for effective architectural design.
- Heat pumps are becoming increasingly common and can vary significantly in type and application, largely depending on climate.
- Engaging with mechanical systems hands-on can significantly enhance understanding and retention of HVAC principles.
- Building relationships with HVAC professionals can provide valuable insights and opportunities for learning and collaboration.
Summary
Introduction to HVAC Systems
The episode begins with an overview of HVAC systems, focusing on how they can be categorized into three main types: air-to-air systems, water-source systems, and air-water hybrid systems. This introduction is prompted by a question from Jessica, an aspiring architect, who is looking to understand more about HVAC systems and their applications.
Understanding HVAC Types and Functions
Bryan dives into the details of various HVAC systems, explaining the primary types—air, water, and air-water systems—and distinguishing between direct expansion (DX) and water-source systems. It includes discussions about split versus package systems, and differentiates between forced air systems like Constant Air Volume (CAV) and Variable Air Volume (VAV).
Detailed Breakdown of HVAC Components
Key components of HVAC systems are discussed including fan coil units (FCUs), chillers, and air handling units (AHUs). The distinctions in forced-air systems, air-to-water systems, and their respective advantages and disadvantages are laid out in detail. With a focus on practical application, Bryan explains the relevance of these systems in modern architectural practice.
Heat Pumps and Passive Systems
This section covers the different types of heat pumps—air-source, water-source, and ground-source—highlighting their efficiency, installation challenges, and appropriate use cases. Bryan also explores the concept of passive systems, which reduce the HVAC load through design techniques without replacing mechanical systems.
Practical Advice for Architects
The podcast concludes with practical advice for future architects like Jessica. Bryan encourages hands-on learning experiences, such as visiting mechanical rooms and observing systems in operation to enhance understanding of HVAC design and implementation. He emphasizes the importance of building relationships with HVAC professionals and taking an interest in the functioning of these systems.
Sponsors
- Carrier · Carrier has been a long-term sponsor of the podcast and their products range from single-stage equipment to the high-efficiency green speed extreme.
- Refrigeration Technologies · Their Viper aerosol coil cleaner is a powerful cleaning solution that is safe to use with or without rinsing and works on both evaporators and condensers.
- Navac · Navac offers the NX1 and NX4 digital manifold gauges which support a wide range of refrigerants and has various operational modes for HVAC needs.
- Filtrete · Filtrete filters have high effectiveness ratings in capturing microscopic particles and maintain airflow across a range of MERV ratings, making them suitable for various HVAC systems.
- AHR Expo · The AHR Expo is the largest HVACR trade event, offering numerous networking opportunities, educational sessions, and product showcases from leading manufacturers.
Show notes
In this short podcast, Bryan answers a question submitted to HVAC School by an aspiring licensed architect who wanted to learn more about the many different types of HVAC systems.
The three main buckets of HVAC systems are air-to-air, water-source, and air-to-water. Air-to-air systems move air around to remove heat from one space, and that heat is rejected to the air somewhere else. Water-source systems move water around the building and use water as the heat rejection medium. Air-water hybrid systems condition the load with water and may use air for ventilation; water or air may be used as the rejection medium. Systems may be direct-exchange (DX) and may transfer heat directly to refrigerant, or they may flow the air or water over a coil with water or glycol, utilizing a secondary fluid. Systems may also have separate indoor and outdoor architecture (split systems), or all components may be rolled into a single box (package unit). Package units include window units, PTACs, and RTUs.
When it comes to forced-air systems, constant air volume (CAV) systems maintain the same volume of airflow (though the temperatures will change). Variable air volume (VAV) systems use one stream of cold air in a main duct, and each zone has a VAV box that functions as a damper to control zones individually. Dual duct systems have one cold duct and one warm duct that run parallel to each other and mix at each zone. Packaged rooftop units (RTUs) are self-contained with ducts that run down into the space and are common in retail spaces.
Air-to-water systems use fan coil units (FCUs) fed with chilled or hot water. Air moves locally inside the space, so there is less ductwork and good zone control, but there are many units to manage.
Chillers make chilled water, and that water is pumped around the building and sent to individual air handler units (AHUs). These are highly efficient and have large amounts of piping. They need mechanical rooms and dedicated personnel to maintain them.
Variable refrigerant flow (VRF) systems are DX systems that are becoming more popular and consist of multiple indoor units with one or more outdoor units. Some of these can be used for heat recovery, meaning one space can be cooled while another is heated.
Heat pump types include air-source, water-source, and ground-source. Air-source heat pumps absorb heat from the air via one unit and reject it via the other; the outdoor and indoor units can swap functions. Water-source heat pumps are common in commercial applications and have multiple heat pumps tied into a water loop that tries to stay within a given temperature range via boilers and cooling towers. Ground-source or geothermal heat pumps pick up heat from the earth's stable temperature and are highly efficient, but they have high installation costs.
Passive systems come in all sorts of varieties and reduce the HVAC system's loads but don't replace HVAC systems in North America. Mechanical systems consist of straight-cool (air conditioner with electric heat), furnaces (gas, propane, or oil combustion), or heat pump (reversible air conditioners) systems.
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