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November 12, 2014
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.
November 12, 2014
The most important factor in selecting a furnace is the contractor you buy it from. A conscientious contractor will specify a furnace that is properly sized for the application, and meets the comfort, efficiency, and budget needs of the customer. A quality installation is then needed to provide quiet operation and balanced heat distribution. Equipment oversizing is the most common cause of noisy, imbalanced, drafty, and inefficient performance.
Efficiency of gas furnaces is measured by the Department of Energy’s Annualized Fuel Utilization Efficiency (AFUE) standard. Older style standing pilot atmospherically vented furnaces achieve an AFUE rating of 50% to 65%. Electronic ignitions improve the rating by about 5%. Modern draft induced furnaces achieve an efficiency rating of 80% AFUE, and condensing gas furnaces achieve an “Energy Star” efficiency of 90% to 97% AFUE. High efficiency furnaces can be vertically or side wall vented with PVC pipe, and require a condensate drain.
Most manufacturer’s offer two stage furnaces at a very small premium. Low stage operates the furnace at two-thirds capacity for the first 10 to 15 minutes of operation. If heat demand is not satisfied in that time, the furnace will step to its full capacity until the space is heated. Staging provides quieter operation, more comfortable heating, higher efficiency, and less cycling of the furnace.
Modulating furnaces provide a range of heating from 40% to 100% of capacity. They provide the ultimate in comfort by equalizing the heat loss of the home with the output of the furnace. They are also ideal for zone controlled installations.
Typical modern furnaces are equipped with direct drive AC blower motors. Premium furnaces now offer digitally controlled direct current (DC) ECM blower motors that operate at a fraction of the energy costs of standard AC blower motors. In addition to efficiency, these blowers offer quieter operation and more precise air volume control. These blowers can also be set for very low constant air circulation volume. This provides extremely quiet operation for air cleaning and stratification reduction.
We will gladly help you select the combination of features that fit the needs of you and your residence or business.