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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 DIAGNOSIS & REPAIR
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
FAN NOISES, HVAC
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
Air Conditioner & Heat Pump Efficiency Ratings: this article explains air conditioning SEER energy efficiency ratings for air conditioners and heat pumps along with related terms like BTUs, Watts and hourly operating cost, in easy to understand language.
Latent heat, superheat, latent heat of vaporization, latent heat of condensation, sensible heat & specific heat and joules are defined separately at
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Definition of SEER - Seasonal Energy Efficiency Ratio
SEER stands for "Seasonal Energy Efficiency Ratio. This is a measure of the energy efficiency of the air conditioning system. SEER ratings permit consumers to compare operating costs of various cooling systems and products.
SEER = [Total Cooling Output Over the Cooling Season] / [Total Electrical Energy Input Over the Cooling Season]
Higher air conditioning SEER rating means more efficient, or in other words lower energy cost to cool the building. Older air conditioning systems are likely to have a lower SEER (perhaps 5 or 6) than a newer more efficient system (perhaps SEER=10). But beyond comparing SEER ratings, a look at the building insulation, air leakage, and the layout, insulation, and adequacy of the air conditioning duct system are likely to have a very large, usually determining effect, on the operating cost of air conditioning systems in buildings.
Here are the U.S. Government's Energy Star Program definitions of SEER and EER: 
The Energy Star Program's SEER and EER definitions and equipment ratings engered some confusion around just what the SEER rating means for individual air conditioner components versus the SEER or EER for the whole A/C system. We report and answer questions about SEER EER and related topics throughout the rest of this article.
Reader question: components in whole AC system energy efficiency
(June 10, 2014) Scott Defelice said:
Hello, I was quoted a 16 seer 2.5 ton system and when installed the label says 14.5 seer. The hvac guy says its because the 16 seer rating is achieved by adding the 14.5 of the condenser and the coil with a txv is 1.5 seer for a total system rating of 16. Is this on the level?
The SEER rating of the equipment is what the manufacturere has printed on its label. I don't understand together SEER ratings for mulitiple individual pieces of equipment and in my opinion that would be a misleading tactic, perhaps intended as a sales gimmick. Give the manufacturer a call and let us know what they say.
Reader Question: relationship of equipment SEER rating and duct system
(Aug 18, 2014) Sam said:
Is there a relationship between the SEER rating and the size of the ducts that deliver the air from the A/C unit to each room? If so, is there a maximum SEER rating to be considered when buying a new unit? If so, what is the size of the duct vs SEER rating?
What an excellent question, Sam.
No ... and yes.
The "no" answer is that SEER is defined based on the equipment itself - and specified by the manufacturer for each product model. The manufacturer can't include possible snafus or variations in HVAC duct design since those are widely variable and an unknown back at the factory.
The "yes" answer is that TRUE HVAC seasonal operational efficiency and thus operating costs will vary widely for the exact same equipment installed under different conditions.
So leaky HVAC ducts, uninsulated ducts, under-sized supply or return ducts, dirty air filters, and similar variables all will have an effect on how long equipment has to run to reach a thermostat set point and thus will affect operating costs.
To be more clear, we need to keep separate the operating efficiency of a compressor/condenser or fan/coil unit themselves from the many factors that affect true heating or cooling costs. I'd argue that factors outside of the manufacturer's box not only are widely variable but can't be included in SEER ratings.
HSPF Heat Pumps Need a Special Energy Efficiency Rating Factor
The Energy Star program also provides a performance rating factor for heat pumps since those units, unlike straight air conditioning systems, operate through both heating and cooling seasons:
Also see our definition at HSPF at the end of this article.
We note that because electrical energy costs vary widely in different areas of North America, and because in some areas the electric utility may give preferential rates (reduced rates) for people using electric heat, the HSPF number may need adjustment for your area.
At Other Heating & Air Conditioning System Performance Measurements & Standards we define other heating and cooling terms such as AFUE and HSPF.
Also see ENERGY STAR PROGRAM and for tips on how to cut air conditioning or heat pump operating costs,
and see AIR CONDITIONING HEAT PUMP SAVINGS.
Standard Required Air Conditioner or Heat Pump SEER Ratings
Currently (2012) in the U.S. new HVAC products are required to have a SEER rating of 13 or better. Equipment is readily available with a SEER of "up to" SEER 16, possibly higher from some manufacturers.
How Much Energy Does an Air Conditioning System Use?
How to Calculate Energy Usage using an Air Conditioner's SEER rating
A concise way to translate SEER number directly into energy cost is SEER 10 = 10 BTUs/Watt Hour. In other words, an air conditioner that has a SEER rating of 10 will provide 10 BTUs of cooling per WattHour (Wh) of operation.
So if our air conditioner has a SEER of 9, it is less efficient than an A/C unit with a SEER of 10 because our SEER 9 air conditioner produces 9 BTUs of cooling for the same Wh of operation. That is, we've kept the energy consumption (one Wh) the same, but we got less cooling output.
Let's define Watts and BTUs so we can better understand these air conditioner figures of SEER efficiency, BTUs, Watts, and air conditioning operating cost calculations.
What is the SEER for Older Air Conditioners?
Older air conditioning systems are likely to have a lower SEER (perhaps 5 or 6) than a newer more efficient system (perhaps SEER=10). But beyond comparing SEER ratings, a look at the building insulation, air leakage, and the layout, insulation, and adequacy of the air conditioning duct system are likely to have a very large, usually determining effect, on the operating cost of air conditioning systems in buildings.
Testing Requirements for SEER Ratings for Air Conditioners & Heat Pumps
According to the ENERGY STAR program requirements,
How do we calculate watts, volts, and amperage for an electrical device like an air conditioner?
Watt hours (Wh), sometimes written W.h, can measure either electrical energy produced, say by a power station, or Watts can measure the amount of electrical energy consumed (say at a light bulb or an air conditioner in our home). For air conditioners, the A/C units' total Wh is the energy used in running the air conditioning system for an hour.
Details are at Definition of WATTS and
Also see DEFINITIONS of ELECTRICAL TERMS for details about volts, watts, amps, and power factor.
Watts (W) as used in a simplified manner here and by electricians, is a measure of electrical power and is expressed by any of the formulas shown below. [All forms of power are measured in units of Watts, W, but this unit is generally reserved for real power (see definitions further below.]
DC circuits: W = V x I (this is a simplified formula and is technically exactly correct for DC circuits. For AC circuits,
AC circuits: Watts W=V*I*PF where PF = power factor
See DEFINITIONS of ELECTRICAL TERMS for details about volts, watts, amps, and power factor.
Also see AMPS & VOLTS DETERMINATION "How to estimate the electrical service ampacity and voltage entering a building".
Reader Daniel Mann adds that "Watts is correctly shown as Watts-Voltage times Current times power factor. Since power factor varies all over the place,..." [W = V x I] "perpetuates misinformation".
We include additional more technical explanation of power factor, real power, apparent power, complex power, and reactive power as we elaborate
Lots of electrical appliances include a label providing the appliance's wattage, and in the case of heating and air conditioning equipment, lots of other details are provided too.
A BTU is a measure of heat energy, or the amount of heat given off when a unit of fuel is consumed. One BTU is the amount of heat energy we need to raise the temperature of one pound of water by one degree Fahrenheit. One BTU also is defined as 252 heat calories (this is not the same as food calories).
When talking about air conditioners or heaters, we talk about the A/C unit's BTUh capacity - the number of BTUs of cooling (lowering rather than raising temperature) it can produce in an hour of running.
When we are heating a building BTUs describe heat given off by consuming fuel or energy from some source (electricity, natural gas, LP gas, oil, etc.) of which some portion is delivered to the building occupied space (see AFUE and HSPF).
When we are cooling a building, or when we are describing an air conditioner or heat pump's rated capacity (in BTUs), we are describing the removal of a quantity of heat from the building - or really from the building's air.
Also see DEFINITION of HEATING & COOLING TERMS where we further discuss and define BTUs, Calories, and other energy measures.
At Definition of BTUs you can see a table of BTUs translated into other measurements:
Based on the definition of BTUs above, BTUH describes the number of BTUs of energy produced (as heat) or removed (by air conditioning) in one hour.
One ton of air conditioning capacity produces the same cooling ability as melting one ton of ice in 24 hours. Sketch courtesy of Carson Dunlop Associates.
288,000 BTUs / 24 hours = 1 Ton of cooling
12,000 BTUs / hour = a 1-ton air conditioning system
A one-ton air conditioner claims to remove 12,000 BTUs of heat from the building air per hour of operation.
Or if we know the total number of BTUs at which an air conditioning system is rated, since this number is usually given in BTUH or BTUs / hour, we just divide that number by 12,000 to get the number of tons of cooling capacity.
A 36,000 BTUh air conditioner is providing 36,000 / 12,000 or 3 Tons of cooling capability per hour.
If we know the number of tons of cooling capacity that an air conditioning system is rated for, we just multiply the number of air conditioning capacity in Tons by 12,000 to get the number of BTUs of cooling capacity of the system.
To assist in choosing the right sized air conditioner, we provide a typical air conditioner chart
Watch out: more is not always better. Don't buy an air conditioner that is too big: if you install a system that is too powerful (too many tons of cooling capacity) the building will be less comfortable than if you install a properly-sized air conditioner. Too many tons of air conditioning mean the system will shut off on short cycles and won't run long enough to reduce the indoor humidity to a comfortable level.
Details are at DEHUMIDIFICATION PROBLEMS
How much electricity our air conditioner uses per hour is easy to calculate. Let's assume that the data tag on our air conditioner says that the unit is a 5000 BTUh device with a SEER rating of 10. This means our A/C unit will produce 5000 BTUs of cooling in an hour of running.
Since SEER=10 means that 10 BTUs used per Wh, then
How Much Electricity Does An Air Conditioner Use in one Cooling Season?
A common example we use (because the math is easy) is to assume we have 125 days of cooling season during which we run the air conditioner for eight hours per day.
So we are using 500,000 Watt Hours of energy (electricity) per cooling season. We divide this by 1000 to convert to Kilowatts since that's how our electrical bill will express our electricity usage.
That's how much electricity we're using over the cooling season.
Reader question: translate difference in SEER ratings into difference in energy costs to operate an air conditioner
(May 28, 2014) Esther Tauber said:
How does the difference of a seer of 16 and 18 translate into cost of electricity
A difference of 2 between two SEER ratings translates into about $13. per year of savings based on an electricity cost of 0.08 U.S. per KWH. The actual electricity cost difference will of course vary depedning on electrical rates in your area.
At OPERATING COST we determine the actual dollar cost of running an air conditioner either by the hour of by the season of use. It's easy to get from that data to actual air conditioning operating costs in dollars.
Also see AIR CONDITIONING HEAT PUMP SAVINGS for suggestions on cutting A/C or heat pump operating cost.
How to Find Out the SEER Rating for Your Air Conditioner or Heat Pump
Reader Question: I'm trying to find the SEER rating on my Carrier condenser.
1/30/2014 Kevin said: I'm trying to find the SEER rating on my Carrier condenser. Is it supposed to be on the data tag somewhere? thanks
Reply: Where the SEER Rating for your HVAC equipment
Good question, Kevin, thanks.
No we do not generally see the SEER rating encoded nor explicit on an HVAC equipment data tag. Rather it is in the product literature.
And by agreement, the HSPF and SEER ratings shall be identical to the levels reported on the Federal Trade Commission (FTC) Energy guide Label. Energy guide labels are usually a large, easy to spot yellow label found on new air conditioners, heat pumps, water heaters, and appliances.
In our discussion of DATA TAGS on AIR CONDITIONERS we noted about EERs and SEERs that
I THINK that a reason for this is that the net SEER rating for a given air conditioner or heat pump depends on how a combination of components operates together while certain individual components might be used in more than one set-up.
SEER Example for Carrier's Infinity Split System Air Conditioners & High Efficiency Gas Furnaces
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