Packaged rooftop heating, ventilating, and air-conditioning (HVAC) systems are found on the roofs of commercial and industrial buildings of all types and sizes. Single-packaged units can cover all the heating and cooling needs of a facility or they can be configured to handle cooling only. A packaged system contains all of the components found in larger HVAC configurations in a pre-assembled, self-contained unit. The advantages of these systems are their simplicity and lower installation cost.While packaged units are typically pre-assembled, they offer options which may be well-suited to the needs of your facility.Natural gas and electric heating options are available in packaged rooftop units. The choice between the two is based primarily on the cost of the unit, as well as operating and installation costs. Natural gas heating units typically have higher overall installation costs when gas piping is included, but are generally less expensive to operate. A gas condensing option is now available.

The added cost of piping natural gas to these units may be recovered quickly, depending on fuel costs and efficiency of the equipment.Commercial packaged rooftop cooling systems in the 5- to 30-ton range are often distributed in several locations along a rooftop, depending on the size of the building and the overall cooling load required. The efficiency of air-conditioning systems is measured using Energy Efficiency Rating (EER) and Seasonal Energy Efficiency Rating (SEER) metrics. A higher rating indicates a higher efficiency level. The most widely used energy-efficiency standard, ASHRAE 90.1-2010, recommends a minimum SEER rating of 13.0 for packaged units of 5 tons or less. Air-cooled units sized at 5 to 11 tons should have a minimum EER rating of 11.2, while 11.0 is recommended for systems ranging from 11 to 20 tons. For units over 20 tons, the minimum recommendation is 9.9 EER.Packaged units include a number of optional features for increasing performance and saving energy:For facilities with multiple packaged units, comfort zoning can improve overall efficiency and increase flexibility to tailor temperature setting for specific building areas.

A low-cost method for improving the efficiency of your current packaged rooftop unit is proper maintenance. These units are constantly exposed to the elements and their energy efficiency decreases over time if the coil and fan aren’t cleaned, the insulation degrades, the compressor wears and/or the overall system deteriorates. ac condensing unit placementThe following maintenance activities help to ensure optimum system performance:A year-round maintenance program can pay dividends. 10000 btu window air conditioner heaterFor example, a unit with a badly fouled coil might operate at an efficiency of 1.6 kW per ton, rather than the designed 1.3 kW. units consumed by 1 ton split acFor a 20-ton unit, that dirty coil could increase energy costs as much as $250 per month or more.

To clean, soap and water will work if done regularly. You might also consider installing an ultraviolet light to help keep the coil clean between scheduled maintenance visits. ASHRAE Standard 180 offers checklists for maintenance tasks of rooftop units.When installing a new packaged system, size the unit to fit your current needs rather than matching the old design. Cooling systems are often oversized for a number of reasons:Oversized equipment is more expensive to install and operate. Frequent compressor cycling often leads to premature equipment failure and higher electricity costs. Oversized fans and duct work also use more energy and cause greater variation in occupant comfort. Work with a qualified engineer or your system installer to make sure it is sized correctly.Customers and employees enjoy the comfort a packaged rooftop unit provides. Facility managers and building owners appreciate lower operating costs and increased equipment performance. Careful planning combined with proper maintenance should help to make everyone happy.

Work closely with your contractor during the installation process and schedule a regular maintenance program.Your electric and gas utilities offer incentives for purchasing energy efficient heating and cooling equipment. For more information, see our Save@Work section.This article has been prepared solely for the purpose of providing helpful information to users of this service. The information has been compiled by Questline, a contractor to the NHSaves utilities; however, no representation is made by either Questline or NHSaves as to the completeness or accuracy of the information contained therein. In particular, some information may be incomplete, may contain errors or may be out of date. In addition, neither Questline nor NHSaves endorses any product or service mentioned therein. Home > Archive > PRODUCT SPOTLIGHT: Rooftop Units PRODUCT SPOTLIGHT: Rooftop Units The latest advances in rooftop heating, air conditioning, and ventilation units. Variable-speed-compressor option RN Series packaged rooftop units are available in capacities of 55 to 140 tons.

Variable-speed, direct-drive, backward-curved plenum fans provide quiet, energy-efficient airflow at all static-pressure conditions. The addition of variable-frequency-drive-controlled variable-speed compressors results in unit efficiencies of up to 16 IEER. —AAON Energy-recovery-wheel option An energy-recovery wheel that recovers approximately 75 percent of energy from an exhaust-air stream is available for Rebel rooftop units. Rebel units without energy recovery achieve integrated energy-efficiency ratios as high as 20.6; the energy-recovery option allows for even greater efficiencies, especially for applications requiring large amounts of ventilation air. —Daikin-McQuay                     Expanded capacity range The Atherion commercial packaged ventilation system now has a capacity range of 7.5 to 30 tons with the addition of a B-cabinet model. Atherion units offer optional high-efficiency gas heating and MERV 16 filtration. —Modine                         High-efficiency package units Available in 7.5-, 10-, 15- and 20-ton sizes, the Prestige Series of commercial package units features MicroChannel coil technology, which uses up to 50-percent less refrigerant than conventional coils.

Some models include variable-frequency-drive supply fans, which save energy by reducing airflow by 50 percent during first-stage cooling and fan-only operation. —Rheem                        Forty-ton scroll compressor Designed for rooftop units and chillers that use R-410A refrigerant, the SH485 scroll compressor features an intermediate discharge valve that adapts to varying loads and ambient conditions, optimizing a system throughout the year. As a result, the SH485 offers up to 24-percent higher part-load efficiency in manifold configurations compared with other compressors. —Danfoss                       Light commercial retrofit unit The Raider is a light commercial rooftop unit designed built to fit the most popular curb sizes currently in use, virtually eliminating the need for an adaptor curb on many replacement jobs. The units are available in 3- to 5-ton gas/electric, electric/electric and heat pump models with efficiencies of 13.0 seasonal-energy-efficiency ratio and up to 11.4 energy-efficiency ratio.

—Lennox Packaged gas/electric unit The PPG2GI iQ drive gas pack is rated at 20 seasonal-energy-efficiency ratio and 81 percent annual-fuel-utilization efficiency. The packaged system uses inverter technology, allowing it to modulate in cooling mode from 40 to 118 percent of capacity in five steps. It is available in capacities of 2, 3, 4 and 5 tons. —Maytag Models up to 150 tons The WeatherExpert Series of high-efficiency rooftop units has been expanded to include models up to 150 tons. The WeatherExpert line boasts integrated energy efficiency ratio ratings up to 20.6. All models meet or exceed all current ASHRAE Standard 90.1 energy requirements, with some models exceeding them by more than 70 percent. —Carrier Enthalpic plate heat-exchanger An enthalpic-plate-heat-exchanger option for VPRC rooftop units provides both sensible and latent energy transfer. Its function is similar to that of a heat wheel, but it is designed to operate with the simplicity and minimal cross-contamination of a plate heat exchanger.