(19 to 73 kW)
Unitary air-conditioning units are self-contained and are commonly sold "off the shelf," either as a single packaged unit or as a split system (see insert).
High-efficiency unitary air-conditioning units provide the same reliable space cooling as standard efficiency models, but they use up to 25 percent less electricity. That's good for your company, and it's good for the environment. Reducing electricity use saves money, and improving energy efficiency reduces greenhouse gas emissions that contribute to climate change.
- A unitary air-conditioner is a factory-made assembly that normally includes an evaporator or cooling coil and a compressor and condenser combination. Unitary systems with one factory-made assembly are called single package systems; those with more than one assembly are called split systems.
- Energy Efficiency Ratio (EER) is a measure of full-load efficiency; the higher the EER, the more efficient the unit. EER represents the ratio of total cooling capacity (Btu/h) to electrical energy input (watts).
- Integrated Part-Load Value (IPLV) is a seasonal efficiency rating that applies to units with stated partial capacities, such as units with staged compressors.
- 1 ton = 12 000 Btu/h = 3.516 kW
This technical note, prepared by EnerGuide for Industry, addresses unitary air-conditioning units sized from 19 to 73 kW (5.4 to 20 tons), the most widely used type of air-conditioning system in industrial and commercial facilities.
High-efficiency air-conditioning units incorporate a number of features to reduce electricity consumption. These include¹
- Condenser. The condenser may be made larger to reduce the condensing temperature and compression ratio.
- Condenser fans. Propeller fans are sized and shaped for efficient operation at full and part load.
- Filters and cooling coil. Coils and filters are larger to reduce the airflow velocity and improve heat transfer. They are also designed to have easy access for cleaning.
- Economizer. Reliable damper controls ensure that maximum use is made of free outside cool air, whenever available. As well, low-leak dampers keep out unwanted air when the dampers are closed.
- Supply-air fan. High-efficiency airfoil blades are used with an efficient motor and adjustable speed drive (ASD).
- Compressors. Multiple compressors may be used and sized to provide efficient operation at part-load.
Currently, unitary air conditioning units (19 to 73 kW) sold in Canada are regulated by Canada's Energy Efficiency Regulations and are required to meet minimum efficiency levels as specified in the Canadian Standards Association's CSA C746-98, Performance Standard for Rating Large Air Conditioners and Heat Pumps. (These regulations are currently under review.) In accordance with commitments made under the Montreal Protocol, the use of HCFC-22 as the refrigerant in unitary air-conditioning units will be phased out in new equipment by 2010.
A number of manufacturers provide high-efficiency air-conditioning models that have significantly higher EERs than the minimum levels required under Canada's Energy Efficiency Regulations. ENERGY STAR® is a voluntary labelling program that has worked with manufacturers to develop a set of specifications that enables buyers to identify these high-efficiency models. Table 1 belowillustrates the improved energy efficiency of an ENERGY STAR unit and the best available unit compared with a typical standard air-conditioning unit in two size ranges.
|Capacity (kW)||Energy Efficiency Regulations Minimum Efficiency²||ENERGY STAR Efficiency Specifications||Best Available Unit|
|19 to 40|| 8.9 EER;
| 11.0 EER;
| 13.4 EER;
|41 to 73|| 8.5 EER;
| 10.8 EER;
| 13.1 EER;
¹ E-Source Cooling Technology Atlas
² ibid Note that the minimum efficiency regulations of Natural Resources Canada's Office of Energy Efficiency are scheduled to be updated to match ASHRAE 90.1-1999. The new minimum efficiencies will regulate units in the range of 19 to 40 kW to have ratings of 10.3 EER and 10.6 IPLV, and units from 41 to 73 kW will have ratings of 9.7 EER and 9.9 IPLV as their minimum efficiencies.
EnerGuide for Industry is an initiative of Natural Resources Canada's Office of Energy Efficiency. Its objective is to provide the industrial-equipment procurement community with information and decision-making tools that will help them to improve their company's profitability while contributing to Canada's energy efficiency and environmental objectives. This technical profile is part of a series; other products profiled include electric motors, electronic high-intensity discharge (HID) ballasts and dry-type transformers.
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