What’s Involved in (Commercial) HVAC?
Nov. 19, 2020
Commercial HVAC refers to anything involved with heating and cooling large properties, such as business buildings, restaurants, rental properties, hospitals, schools, and more. Because of the scale, commercial HVAC heavily differs from its residential counterpart in terms of size, capacity, and operational complexity. In this article, we’ll dive into some of the core components of commercial HVAC and what these technicians are typically working with.
Simple vs. Complex Systems
One of the most important concepts in commercial HVAC is around understanding simple systems, compared to complex systems. Simple systems use direct expansion cooling or heating. They directly heat or cool a refrigerant to heat or cool air. Most of these systems have a main furnace that heats electricity, oil, or gas. Simple systems serve an area or zone and have a direct control unit within this zone.
Complex systems transfer the heating and cooling function to a secondary unit. They cool spaces by putting the refrigerant in a chiller and circulating water through the cooling coils. They warm spaces by generating hot water or steam in a boiler. This steam or hot water is circulated by means of heating coils. Complex systems have a centralized operating unit and serve multiple zones.
3 Types of Simple HVAC Systems
Single Split Systems
These are the most common HVAC systems on commercial properties. They’re most often used in small buildings, and require manual operation to heat and cool different spaces. They consist of several air conditioners that distribute air to different furnaces and refrigeration lines across the system. Air is circulated to different spaces through air ducts. Each unit of a single split system is controlled separately, and each system has their own outdoor unit.
Often, single split systems have a decentralized heating and cooling structure. The heating and cooling are done through units that are operated individually. While easy to manage, they’re not suited to large properties. The main advantage of single splits is that if one unit breaks down, the other will still work. However, they eat up a lot of space if you install several of them on a property.
Multi-split systems are similar to single splits, but are more energy efficient. They allow property owners to connect a single outdoor unit to several heating and cooling systems. In addition, they have sensors to detect changes in temperature, so they can automatically counter changes. Their heat pumps are designed in a way that the air in the system follows the natural flow, and because of that, they consume less energy per unit than single split systems.
Most multi-split systems have centralized heating, which controls heat supply to entire buildings. The centralized system allows for high load management and is easy to control. However, such systems are very complex and require specialized skills to operate, maintain, and install. Because HVAC systems waste a lot of heat while they’re being turned on and off, multi-split systems have sensors that regulate the temperature, eliminating the need to turn the system on and off. This saves a lot of energy, which can save significant amounts of money, especially in larger buildings.
Multi-splits have heat pumps that are more energy efficient than conventional air conditioners and furnaces. They also require more pipework during installation than single splits. However, they require less outdoor space than single splits because one outdoor unit can serve nine HVAC systems.
Variable Refrigerant Flow (AKA Volume Systems)
VRF systems heat and cool different parts of the property at the same time. They collect waste heat from the warmer spaces and direct it towards the cooler areas. They are most suited to properties with several rooms and large open areas. Most VRFs are used in large properties with mixed uses.
Components of Simple HVAC Systems
Commercial HVAC involves two main types of heaters:
- Radiant heaters: Warm spaces through infrared radiation.
- Furnace system: Burn fuel to generate heat that warms the property.
There are two types of ventilation used in commercial HVAC.
- Mechanical ventilation: In this setup, fans suck in outside air and distribute it into the space that needs circulation. The system uses both outside air and recirculated air to refresh these spaces. US energy codes have regulations for the minimum outside air that should be used in a property. The minimum is based on the number of occupants and square footage
- Natural ventilation: Systems that rely on natural ventilation have no fans, they simply rely on the natural flow of air from higher pressure to lower pressure spaces.
There are generally two types of air conditioning found in commercial HVAC.
- Refrigerant-based systems: These have a refrigerant mechanism that moves heat from inside to out, thus cooling off the space. The refrigerant goes through several cycles of evaporation and condensation to cool a space.
- Non-refrigerant: They heat and cool spaces through the evaporative cooling of water.
Components of Complex HVAC Systems
Complex HVAC systems typically have the following within the central plant:
- Boilers: These generate warm air through heated water, which is stored in a tank.
- Cooling towers: These are heat exchangers, that use water and air to remove heat from heavy HVAC equipment. They disperse the heat outside.
- Chillers: These remove heat from a liquid via a vapor-compression. This liquid can then be circulated through a heat exchanger to cool equipment, or another process stream (such as air or process water).
- Natural Gas
Complex systems have a hydronic distribution system, where heated water or steam is transported to secondary heating units located in different parts of the building. The ductwork then distributes hot or cold air around the property. Complex systems are more expensive than simpler systems, but they are more efficient than their simpler counterparts.
Commercial HVAC Location
Most commercial HVAC systems are placed on the roof of the property. This helps save space and reduce noise pollution because these systems can be pretty loud. Having them on the roof also makes it easier to perform maintenance and repair without disturbing people working inside the building. Further, most commercial HVAC systems are modular, meaning that new units can be added to the system as the number of users increases. If the systems are on the roof, there’s less impediment to the workday occurring below, as new units are installed.
Commercial HVAC often requires a lot of project management, as projects can take weeks, or even months to complete. Managing labor is no easy feat, and it’s really important to ensure you have the right people on the right tasks, day-by-day.
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