When rooftop units were first introduced some forty years ago, they were considered by system designers and building owners to be a bare bones, low cost, simple solution to low-rise building HVAC needs. Low cost was the primary motivator for both manufacturers and users. But while they were popular with designers and owners, many maintenance managers considered them nightmares: not easy to service, prone to breakdowns, inadequately protected from components.
Today, everything has improved. Gone is the concept of one size fits all. Buyers have more options, including practically every one of the same features found some other types of building HVAC systems, from economizers for energy conservation and prewired interfaces for building automation systems to heat wheels and other heat recovery devices. No longer can the systems be called bare bones.
What has contributed for this change has been a shift in focus from first costs to life-cycle costs by both manufacturers and users. The result has been the impending new rooftop systems incorporate features to make them more efficient and in order to maintain.
The typical rooftop unit today comes in one of two configurations: single-zone or VAV. Single-zone systems remain the extensively used. They are low-pressure systems give a constant quantity of airflow to an individual zone controlled through single thermostat. As they definitely do not include controls for multiple zones, this connected with rooftop unit is most effective for use on the inside areas with fairly uniform heating and cooling loads.
The VAV configuration is gaining popularity, primarily as effect of its ability to provide multiple areas, each with different hvac loads. The typical VAV rooftop unit supplies air through a constant temperature a new distribution system that includes VAV boxes to modify airflow into each different area. The VAV configuration helps units more flexible while improving their operating efficiency.
Rooftop units are available today in a wide range of capacities and configurations. The most common cooling configuration uses a DX system, with air or water cooling. Operating efficiencies for air-cooled units range between a definite.0 and 1.5 kW per ton, and between 0.80 and firstly.0 kW per ton for water-cooled units, including all fan and pump energy begin using. Units can also be configured to use externally generated chilled water. Today's typical rooftop unit is 30 percent more advantageous than those of earlier generations.
Rooftop units may use hot water, steam, natural gas or propane for heating, with capacities starting from 40,000 to much more 2 million Btu for natural gas and propane units, and up to 4 million Btu for steam brands.
Some of the most frequent complaints about rooftop units have comes from maintenance personnel. Early generation systems simply were not to be able to maintain. Access panels were held in place with sheet metal screws. Panels often were not replaced properly and screws were lost, exposing the interior for this unit to components. With time, the protective finishes on the exposed panels broke down, resulting in rusting and further exposure of unit components to the elements. Removable panels were often dropped during removal or reinstallation, resulting in harm to the building's house top. But perhaps the most serious drawback was that the units were not designed to make maintenance easy. For a result, proper maintenance was rarely competed.
New rooftop unit designs facilitate maintenance. Exterior panels are protected by an epoxy finish that resists the elements, practically eliminating rusting issues. Machine screws have been replaced with hinged panels and latches, allowing easier access and more secure fastening of expertise. Electronic diagnostic panels have been included in some system designs to help ease system setup and troubleshooting. The net result is that rooftop systems provde the same advantages as earlier generation systems - including low first costs, factory assembly and easy installation - without sacrificing performance or ability.
Rooftop units are suited for inside of practically any low-rise application, such as in retail and institutional facilities. They are particularly well intended for applications where flexibility is required, such as frequent reconfiguration of interior spaces and operations.