Houston Heating, Cooling, and Electrical

What HVAC Systems Are Available For Commercial Buildings?

Commercial HVAC systems are larger and more powerful than residential systems, but they are also designed for efficient, reliable operation. There are several commercial HVAC options available, including variable-air-volume systems, heat pump systems and systems that rely on cooling towers, chillers and boilers. Some commercial HVAC systems are designed for rooftop installation, while others are intended for group installation.

There isn’t a single best choice for every commercial building, so here are the most common systems, and the advantages they offer:

1. Variable-air-volume (VAV) systems – Most HVAC systems use constant air volume (CAV) technology, which means the system draws in a steady volume of air, no matter its temperature.

VAV systems take the opposite approach. Instead of varying the temperature, VAV systems vary the intake air volume while keeping a constant air temperature. To do this, the system takes in outside air, passes it through a filter and then through a supply air fan. The fan is designed for variable speeds, so it can increase or decrease air volume as needed. This treated air is sent through ductwork to different zones in the building, each managed by a “VAV box.” VAV boxes are built with fans and dampers that allow for precise airflow control into each zone. So, for example, if cooling demands are low, the VAV box can use the damper to reduce air flow into the room, or engage the fan to keep air circulating without extensive cooling.

VAV systems possess several advantages of CAV systems, including precise temperature control, reduced energy consumption and reduced compressor wear.

2. Chiller boiler systems, with air handlers – Chiller boiler systems are ideal for smaller commercial buildings, and use both air and water to provide climate control. In this system, the chiller, which is usually located in the basement or on the lowest level, uses refrigerant to exchange heat between water returning from the cooling tower and water returning from the air handler units. The refrigerant facilitates this heat exchange, but it’s run in a separate loop that doesn’t contact the water at any point.

The water, now chilled to low temperature, is sent back to the air handler units. Air handlers are installed on every floor, and they contain a set of coils that the chilled water is sent through. A blower fan directs ambient air over these coils and then into the building to provide comfort. If heating is required, this process can be run in reverse to send warm water to the air handlers.

Warmed water, now carrying heat exchanged in the chiller, is circulated using pumps to a cooling tower. Cooling towers are normally installed on top of the building, and inside the tower, the water is misted and mixed with air so that heat can be exchanged between the water and the air. The warmed air is vented through the top of the tower, the cooled water is sent to the chiller again and the cycle begins again.

Boiler chiller systems are energy efficient and flexible, so they can be designed and installed in a variety of building layouts. If only cooling is needed, the system can be built with a single circulating loop, but if heating is also required, an additional loop will be needed. This increases the cost and complexity of the system, but it remains energy efficient regardless.

3. Heat pump systems with boilers – Though the name suggests otherwise, heat pump systems do not just provide heating. Depending on the direction of operation, a heat pump system can either remove heat from inside the building and move to the outside, or pick up heat from cold air outside and move it inside.

Heat pump systems use the traditional refrigeration cycle to do this, so the same technology found in residential systems. The warm liquid refrigerant is directed to an expansion valve, which reduces refrigerant pressure, and therefore the refrigerant’s temperature. The refrigerant, now in a gaseous state, is sent to the evaporator coils and intake air is pushed over those coils to cool it. The cooled air is then sent to the proper zone for climate control. The warmed, gaseous refrigerant then goes to a compressor, where the pressure is increased and the refrigerant is changed back to a hot liquid. The hot, liquid refrigerant then goes to condenser coils, air is pushed over these coils and then direct out of the building to exhaust the heat. The cycle then begins again.

In a heat pump system, this cycle can be used for heating or cooling, depending on how refrigerant flow is directed. Heat pumps can be installed as packaged rooftop units or as a split system, like those found on residential properties. Since heat pumps transfer heat from low concentrations to high concentrations, they work best in mild climates. The colder the weather, the harder the pump has to work, but in climates like those near the Gulf Coast, this is rarely an issue.

Heat pumps are extremely energy efficient, are inexpensive to operate and maintain and use electricity, so they don’t need to burn fuel to produce heat.

Commercial HVAC systems are impressive pieces of climate control technology, with hundreds of components working together to provide clean and comfortable air. To determine which system will work best for your building, consider working with an experienced HVAC technician, as these climate control experts can develop a system for any building.

FAQ

What are the advantages of a rooftop HVAC system?

Rooftop systems confine all of the system components to the building’s roof. This allows for design flexibility, as the roof is usually an unutilized space. Further, rooftop systems create less noise pollution, improve security, allow for easier maintenance and keep dirt and other debris out of the system.

Rooftop HVAC systems, though, are exposed to the sun, rain, wind and hail, so weather damage becomes a concern. Frequent inspections can resolve this concern.

Why are heat pump systems ideal for warmer climates?

Heat pump systems move heat against the thermal gradient, which means heat pumps must work harder when temperatures are colder outside, as there’s less heat to capture.

That’s not a problem in warmer climates that have mild winters. In these areas, the mild winter means there’s more heat to move from the outside to inside the building.

How can building owners maximize their HVAC investment?

HVAC technology is rated for more than a decade of performance when maintained properly. Frequent inspections and maintenance, provided by a certified technician, ensure the system’s mechanical and electrical components are optimally and safely functioning. This will ensure property owners get maximum value from their HVAC technology.

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