Different Types of Air Conditioning Systems.

This fact sheet focuses on air conditioning equipment and related system considerations for small to mid-sized commercial facilities. Several of the most common systems are discussed below.

Unitary Heat Pumps and Air Conditioners

Breakdown of Cooling Loads in a
Commercial Office Building in the Phoenix Area

The most common types of air conditioning equipment are unitary air conditioners and heat pumps. “Unitary” refers to the fact that all of the components necessary to heat, cool, dehumidify, filter and move air are included in one or more factory-made assemblies. Unitary equipment is available as single package or as split systems. Single package units include all of the necessary functions and components in one package that is installed outside the building. Split systems are made up of an indoor unit (fan and cooling/heating coils) and an outdoor unit (condenser and compressor). Unitary equipment includes heat pumps and air conditioners with integral or separate gas or electric heating systems. Heat pumps provide both heating and cooling from the same unit and are the most efficient devices for low desert areas of Arizona. Air conditioners provide cooling only and must be supplemented with either an internal electric or gas-heating coil or with a totally stand-alone heating system.

Evaporative Cooling Systems

Evaporative coolers provide cooling by blowing hot, dry air over a wetted pad and cooling the hot air by the process of evaporation. In doing so, the humidity of the air entering the conditioned space is increased. The most common form of this technology is direct evaporative cooling otherwise known as a “swamp cooler.” Another form is indirect evaporative cooling that eliminates the problem of increasing the humidity level of the air by using a heat exchanger. Indirect/direct systems that combine these two approaches to improve effectiveness while limiting humidity are also available. Due to Arizona’s arid climate, evaporative cooling can be a viable low-cost technology in many commercial applications. Direct systems use 60 to 80 percent less energy than a heat pump or air conditioner.²

Understanding Heating and
Cooling Equipment Performance Ratings

SEER – The Seasonal Energy Efficiency Ratio is a representation of the cooling season efficiency of a heat pump or air conditioner in cooler climates. It applies to units of less than 65,000 Btuh capacity
EER – The Energy Efficiency Ratio is a measure of a unit’s efficiency at full load conditions and 95 degrees outdoor temperatures. It typically applies to larger units over 65,000 Btuh capacity.
HSPF – The Heating Season Performance Factor is a representation of the heating efficiency of a heat pump in cooler climates.
COP – Coefficient of Performance is the measure of heating efficiency of a heat pump at a constant temperature of 47 degrees.
Btuh – Btuh or Btu/h is a rate of heating or cooling expressed in terms of British Thermal Units per Hour.
Ton – One ton of cooling is the energy required to melt one ton of ice in one hour. One ton = 12,000 Btuh

Air Conditioning System

An air conditioning system includes more than just the air conditioning unit itself. A complete system also includes the air distribution system (ductwork, dampers, grilles and registers), and the temperature and schedule control system. Each of these components makes an important contribution to the performance and efficiency of the system as a whole. In order to operate efficiently, a system needs to be properly sized and installed. Oversized units cost more to operate and do a poor job of comfort control, and poor installation can dramatically reduce the as-installed efficiency of the system (see the chart below for a presentation of as-installed efficiencies). A quality installation will have properly sized ductwork that is sealed with mastic to reduce air leakage to a minimum, balanced airflow throughout the building, and proper refrigerant charge and airflow. The controls are also an integral part of the system and should include programmable thermostats and timers for scheduling of air conditioning equipment or a computerized energy management systems (EMS).

² Commercial Space Cooling and Air Handling, E Source, 1997.

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