Buying an Air Conditioning System

Central air conditioning is available either as packaged units (combined condensor and blower) or as split systems (remote condensing unit with indoor blower coil or furnace). As with heating, sizing is the most critical element of unit selection. Other important considerations are efficiency, noise levels, type of refrigerant, and staging.

Cooling system efficiency is measured by the Seasonal Energy Efficiency Ratio (SEER). Use the SEER number to gauge the relative energy cost of cooling among different combinations of condensers and coils. The minimum allowable SEER rating is 13. We recommend a minimum rating of at least 14, and have systems available as high as 20.5.

Sound levels of condensing units are measured in decibels (dB). Equipment rated at or below 70 dB is considered very quiet. Equipment above 80 dB is very noisy. The scale is logarithmic, so an 80 dB unit is ten times as loud as a 70 dB unit. Selection of quiet equipment, as well as careful placement away from noise sensitive areas, will avoid neighbor’s complaints.

Central air conditioning equipment is now widely available with R410A refrigerant. R22 is being phased out as an ozone depleting chemical. The new refrigerant is ozone friendly and performs very well in equipment designed for its use.

Condensing units are available with either single or two stage compressors. Two stage equipment is very useful in zonally controlled applications to prevent individual zones from overcooling during partial demand.