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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
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
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
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
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
Guide to heating & cooling duct work supply air flow adequacy, flow rate, temperature, and related problems. This chapter of "How to Inspect the Central Air Conditioning or Cooling System" describes the inspection of heating and air conditioning (HVAC) duct registers & zones for defects such as missing air conditioning cool air supply or return air registers, undersized air conditioning duct openings, improper cooling duct routing, cooling (or heating) air duct corrosion, leaky air duct connections, defective heating or cooling ductwork materials such as Goodman gray flex-duct, some Owens Corning Flex-duct, and asbestos-containing air conditioning or heating duct work.
The photograph above shows a 1930's heating and cooling air supply register still in active use, but with leakage around the register which transmitted odors and mold from the building basement. Also see SUPPLY DUCTS & REGISTERS and see LEAKY DUCT CONNECTIONS.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Leaks in HVAC cooling or heating air supply ducts mean that cooling or heating costs are increased, since the HVAC system needs to run longer to reach the desired indoor temperature and humidity. Where more severe supply air duct leaks are occurring, some areas of the building or even the entire building may receive no heated or cooled air at all, even though the equipment is running.
Technical note: The D'Arcy-Weisbach equation for pressure and head loss can be used to calculate the actual pressure loss due to friction in a building piping or air duct system. The Engineering Toolbox provides the D'Arcy-Weisbach formula: Δp = λ (l / dh) (ρ v2 / 2) where Δp = pressure loss (Pa, N/m2), and l = length of duct or pipe (m) and dh = hydraulic diameter (m) and finally, ρ = density (kg/m3).
Watch out: But keep in mind that even this apparently accurate calculation of the effect of piping on air pressure and airflow loss will not include the effects of leaks or obstructions in the building return air or supply air duct system such as the following:
Use the links at left or page top to continue reading about duct defects with the next section: registers and zones.
The master document, of which this is a chapter, describes the inspection of residential air conditioning systems (A/C systems) to inform home buyers, owners, and home inspectors of common cooling system defects. Asbestos or mold in or on HVAC ducts are a possible hazards for which we provide links separate documents - see "Asbestos HVAC Ducts" at below left.
Frequently Asked Questions (FAQs) about leaks in HVAC supply ducts
Questions & answers or comments about inadequate supply air in HVAC duct systems and its effect on heating or cooling air flow adequacy.
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Technical Reviewers & References
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