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InspectAPedia ® Home AIR CONDITIONING & HEAT PUMP SYSTEMS A/C - HEAT PUMP CONTROLS & SWITCHES AIR CONDITIONER COMPONENT PARTS AIR CONDITIONER TYPES, ENERGY SOURCES AIR FILTER EFFICIENCY AIR FILTERS, FIBERGLASS PARTICLES AIR FLOW MEASUREMENT CFM APPLIANCE EFFICIENCY RATINGS BLOWER DOORS & AIR INFILTRATION BLOWER FAN CONTINUOUS OPERATION BLOWER FAN OPERATION & TESTING BOOKSTORE - Air Conditioning "How To" Books CAPACITORS for HARD STARTING MOTORS CAPILLARY TUBES CLEANING & Legionella BACTERIA CHINESE DRYWALL HAZARDS CONDENSATION or SWEATING PIPES, TANKS DEFINITION of Heating & Cooling Terms DEW POINT CALCULATION for WALLS DEW POINT TABLE - CONDENSATION POINT GUIDE DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP DIAGNOSE & FIX HEATING PROBLEMS-BOILER DIAGNOSE & FIX HEATING PROBLEMS-FURNACE DUCTS - Asbestos DUCT INSULATION, Asbestos Paper DUCT INSULATION for SOUNDPROOFING DUCT SYSTEM NOISES DUCTS, Asbestos Transite Pipe DUST, HVAC CONTAMINATION STUDY ELECTRIC MOTOR OVERLOAD RESET SWITCH EVAPORATIVE COOLING SYSTEMS FAN LIMIT SWITCH FAN NOISES GAS EXPOSURE EFFECTS, TOXIC GAS DETECTION INSTRUMENTS HEAT LOSS (or GAIN) in buildings HEAT LOSS (or GAIN) INDICATORS HEAT LOSS R U & K VALUE CALCULATION HEAT PUMPS HEATING SMALL LOADS INSPECTION CHECKLIST - OUTDOOR UNIT INSPECTION LIMITATIONS, A/C SYSTEMS LEED GREEN BUILDING CERTIFICATION LOST COOLING CAPACITY LOW VOLTAGE TRANSFORMER TEST MOTOR OVERLOAD RESET SWITCH MOLD in AIR HANDLERS & DUCT WORK OPERATING COST, AIR CONDITIONER OPERATING DEFECTS, AIR CONDITIONING REPAIR GUIDE, AIR CONDITIONERS / HEAT PUMPS REPAIR & DIAGNOSTIC FAQs for A/C SWAMP COOLERS THERMOSTATS, HEATING / COOLING THERMOSTATIC EXPANSION VALVES WATER COOLED AIR CONDITIONERS WINDOW / WALL AIR CONDITIONERS WINDOW / WALL A/C SUPPORTS More Information |
Retrofit or add-on air conditioning specifications: this air conditioning repair article discusses the Sizing of Retrofit Conditioning Air Handlers: How to Add Air Conditioning to Hot Air Heating Systems. We describe the central air conditioner operating problems that occur if an add-on air conditioning component (to an existing hot air heating system) is not properly sized for the building or if it is not properly matched to the pre-existing blower or air handler system that was used for central heating. There may also be a need for an air handler blower fan capable of operating at different speeds for heating versus cooling. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman. ADDING A/C: RETROFIT SIZING - Air Conditioning Retrofit Errors When Adding Air Conditioning to an Existing Hot Air Heating System: Improper Air Conditioning Cooling Coil Size
The typical indoor half of an air conditioning system is comprised of a blower fan which moves building air (through return ducts) across an evaporator coil (which cools and dehumidifies the building air) and then through supply ducts to various building rooms. Liquid refrigerant is metered into the evaporator coil where it evaporates or changes state from a liquid to a gas. This state change from liquid to gas absorbs heat and thus cools the evaporator coil. As air is cooled by moving across the evaporator coil, moisture is removed from the air (cool air holds less moisture than warm air). The condensate is moved to an acceptable disposal point, perhaps by a condensate pump to a building drain. But a larger evaporator coil does not necessarily mean we'll see an equivalent improvement in the cooling capacity of the air conditioning system. In fact if the cooling coil is too large for the air handler or "blower unit" the air conditioning system will not work properly. The photo shows that an evaporator coil has been added atop an existing heating furnace. Using the existing blower and duct work and simply adding an evaporator coil atop the unit is a common way to add air conditioning to an existing furnace and duct system, and such air conditioning retrofits can work quite well by taking advantage of an existing duct system and air handler. But to work properly the evaporator coil (or cooling coil) should not be too large for the air movement capacity of the existing air handling system. Otherwise the air handler won't be able to move enough air across the evaporator coil to prevent freeze-ups and the net result may be less cooling capacity rather than more. In other words, when the new evaporator coil for an add-on air conditioning system is too large, the blower will not move enough air across the coil, probably leading to the evaporator coil becoming blocked by ice. Similarly, the air movement capability of the blower assembly, including the speed of the fan of an existing furnace needs to be matched to the evaporator coil's needs. The speed of air flow through ductwork and its delivery into a building are different for heating than for cooling a building. Some contemporary combination units which provide both heating and cooling air to a building make use of a dual speed or variable speed fan. If when inspecting a "retrofit" air conditioning system (like the one in this photograph) you see that the evaporator coil is much larger than the furnace blower atop which it sits, the system is probably not properly designed and it may not work correctly. An expert air conditioning service technician or design specialist should evaluate the system when you see this condition. Frequently Asked Questions (FAQs)No FAQs have beenn posted for this topic. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia. Ask a Question or Search InspectApediaQuestions & answers or comments about how to properly size & install retrofit or add-on air conditioning to an existing warm air furnace. Ask a Question or Enter Search Terms in the InspectApedia search box just below. Technical Reviewers & ReferencesRelated Topics, found near the top of this page suggest articles closely related to this one. Click to Show or Hide Citations & References
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