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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 COP, definitions, efficiency, true electricity cost calculations. This article defines heat pump COP (coefficient of performance) and explains why the operating efficiency of heat pumps varies as a function of outdoor temperature. We include a table of factors used to convert electricity costs to true electricity costs as a function of outdoor degree days in the heating season - a calculation that makes comparison of heat pump operating costs with those of other heating methods much more accurate. Illustration at page top provided by Carson Dunlop Associates.
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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.
The COP or co-efficient of performance for a heat pump can be expressed as a curve showing energy consumed to operate the equipment versus the amount of heat energy provided to the building.
Because COP curves show that we cannot continue to make effective use of a heat pump at very low or very cold outdoor temperatures, a backup heating system is required where heat pumps are installed in cold climates.
Illustration provided by Carson Dunlop Associates.
[Click any image to see an enlarged version and to read details.]
Watch out: As we explain in details at HEAT PUMPS, GROUNDWATER, you can't tell which COP and EER measurement for groundwater based heat pump systems is "right" without additional data describing the testing conditions.
The balance point in a COP curve for a heat pump describes the point beyond which it is not efficient to continue to run the equipment to try to heat a building - because we are obtaining less heat energy to put into the building than the energy we are using to operate the equipment.
Illustration provided by Carson Dunlop Associates.>
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 outdoor 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.
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