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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
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM & DUCT DEFECTS
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 GUIDES A/C / HEAT PUMP
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
Heat pump system inspection, basics of operation, troubleshooting & repair guide. This article series answers most questions about heat pump system troubleshooting, inspection, diagnosis and repair. We explain how heat pumps work to provide cooling in hot weather and heating in cool or cold weather. We explain the concept of coefficient of performance or COP, and how the COP balance point determines how much use can be made of a heat pump in different climates.
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How the Heat Pump Works When in Cooling Mode = Summer Mode
Below we illustrate the heat pump operation when the equipment is in heating mode.
How a Heat Pump Operates to Extract Heat from Outdoor Air When in Heating Mode = Winter Mode
Illustrations below provided by Carson Dunlop Associates.
Different or Additional Controls Required for a Heat Pump vs an Air Conditioner: Refrigerant Expansion Devices
Reversing Valve and Defrost Cycle Operation Procedure for Heat Pumps
What is an "All Electric" Heat Pump System? - Compared with Gas or Oil Backup Heat
How does a Water Source Heat Pump System Work?
How does a Ground Source Heat Pump System Work?
Sketch of a Triple Split System Heat Pump System
How does a Bi-Valent Heat Pump System Work? Three Operating Modes all using the outdoor coil
What is the COP or Coefficient of Performance of Heat Pumps?
The COP or coefficient of performance describes the ability of a heat pump to extract heat from outdoor air down to some low temperature, typically 25 degF. for modern equipment. The COP determines how effective a heat pump can be at providing heat during cool or cold weather.
Details including a definition of COP, an explanation of the heat pump balance point, and how to calculate heat pump operating cost more accurately by considering degree days are at HEAT PUMP COP - Definition, sources of variation in heat pump operating efficiency & cost
Heat Pump operating cost variables & COP Calculations
Where a heat pump is used to provide part of the building's heat requirements, the efficiency of the air-to-air heat pump will be less at lower temperatures. Spies (1971, 1977)  notes that heat pump efficiency when outdoorr air is warm is quite different from at cold temperatures, making its use of electricity more complex.
The coefficient of utilization may be as high as 3.0, falling to 1.0 as outdoor temperature approaches 10 degF. In 1971 when Spies wrote that note for the Small Homes Council, few heat pumps worked at temperatures that low, Also that this was in 1971, newer equipment is capable of efficient heat extraction from colder air. Spies provided a calculation to transfer heat pump efficiency or COP into electrical costs when comparing heating fuel type cost alternatives:
Example: If you live in a climate in which the average number of degree days in the heating season is 4000, then to compare heat pump operating costs (using electricity) to other fuels and heating methods,
List of Heat Pump Inspection, Diagnosis, & Repair Articles
Also see AIR CONDITIONING & HEAT PUMP SYSTEMS where we introduce and illustrate the basic components of air conditioners and heat pumps.
Heat Pump Stopped Heating or Cooling - Diagnostic Guide
If your heat pump system has lost its cooling capacity or won't start select one or more of the diagnostic articles listed below.
Frequently Asked Questions (FAQs) about heat pumps
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Questions & answers or comments about how to diagnose & repair residential heat pump systems
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.