To become familiar with and understand how energy consumption values are expressed in HVAC equipment.
1. Understand the meaning of abbreviations used in heating, ventilation and air conditioning equipment (HVAC) manuals.
2. Understand how the figures used in HVAC manuals are correlated into energy usage.
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Everyday we are given new abbreviations for terminology and comparative numbers. Very few people understand what these "buzzwords" mean or what the number next to it means.
The following acronyms will be defined and explained.
10). Sensible Heat
11). Latent Heat
12). Relative Humidity
13). Dew Point
GLOSSARY OF - */-*
* SEER (Seasonal Energy Efficiency Ratio) -
The total cooling of a central unitary air conditioner or unitary heat pump in Btu's during its normal annual usage period for cooling divided by the total electric energy input watt-hours during the same period.
This calculation was developed by the U.S. Department of Energy (DOE) in an effort to simulate actual operation of systems in the field. The test is more complicated than Energy Efficiency Ratio (EER) and uses a number of operating conditions, including cycling. The test may have a calculation substituted for cycling and that causes more credibility loss. Tables 3, 4 and 5 (see below), illustrate test conditions. Also included in calculation is the electricity used by the indoor blower motor, outdoor fan motor, and compressor when matched with a specific indoor coil. Seasonal Energy Efficiency Ratio (SEER) is used for all ducted systems producing up to 65,000 Btu's of cooling.
* *-* (Energy Efficiency Ratio) */-*
A ratio calculated by dividing the cooling capacity in Btu's per hour (Btuh) by the power input in watts at any given set of rating conditions, expressed in Btuh per watt (Btuh/watt).
The calculation is based on a test of the system at constant operation with an outdoor temperature of 95°F. and 50% relative humidity. The indoor temperature used is 80°F and 50% relative humidity. The total of the electricity used for the entire system with a specific indoor coil is the divisor for the formula.
- 36000 BTU A/C using 4500 watts of electricity
36000/4500 * 8.00 EER.
* *-* (Heating Seasonal Performance Factor) - */-*
The total heating output of a heat pump during its normal annual usage period for heating divided by the total electric power input in watt-hours during the same period.
This calculation was developed by the Department of Energy in an effort to simulate actual operation of systems in the field. The test is more complicated than COP and uses a number of operating conditions including defrost and cycling. Also included in the calculation is the electricity used by the indoor blower motor, outdoor fan motor and compressor when matched with a specific indoor coil. HSPF is used for all ducted systems producing less than 65,000 Btus of cooling in cooling mode. Tables 3, 4 and 5 illustrate test conditions.
* *-* (Coefficient of Performance) - */-*
A ratio calculated by dividing the total heating capacity provided by the refrigeration system, including circulatory fan heat but excluding supplementary resistance (BTU's per hour), by the total electric input (watts) X 3.412.
COP is used for a steady operation at a specific outdoor temperature with the indoor temperature at 70°F and 57% relative humidity. The 3.412 constant is the amount of Btus one watt of electricity will generate with resistance heat.
- 42500 BTU output using 6600 watts
42500/(6600x3.412) * 1.9 COP
**-* BTU (British Thermal Unit) */-*
The amount of heat required to raise the temperature of one pound of water (about one pint) by one degree Fahrenheit.
A practical example would be the energy contained in one wooden kitchen match completely burned.
**-* SR (Sound Rating) */-*
Is a tone corrected A-weighted sound power level expressed in bels. The Sound Rating is based on tests performed at Standard Rating Condition (cooling).
• The bold terms used above, a portion of the Glossary on page 8 of the ARI Unitary Directory, August 1, 1992 - January 31, 1993, are reprinted by courtesy of the Air-Conditioning and Refrigeration Institute, ARI.
** *-* (Annual Fuel Efficiency Ratio) - */-*
The ratio of annual output energy to annual input energy which includes any non-heating season pilot input loss, and for gas or oil fired furnaces or boilers does not include electric energy. The ratio is based on 5200 annual average heating degree days and 4600 average non-heating season hours per year for pilot use. The degree days are a result of a long and complicated calculation.
** Definition reprinted by permission of American Society of Heating, Refrigerating and Air-Conditioning Engineers from ANSI/ASHRAE 103-1988 Methods of Testing for Annual Fuel Utilization Efficiency of Residential Central Furnaces and Boilers.
*-* (In cooling or refrigeration) - */-* to 12,000 Btuh (BTU per hour).
*-* Heat - */-* given off or absorbed in a process other than a change in temperature. It cannot be measured with a thermometer, but affects the feel of the air.
*-* Heat */-* Heat given off or absorbed in a process of temperature change. Easily stated, heat that can be measured with a thermometer.
*-* Humidity */-* The ratio (percentage) of the amount of moisture in the air to the amount it can hold at saturation.
*-* Point */-* The temperature at which the moisture in the air will begin to condense.
The preceding paragraphs define the acronyms used in the HVAC industry. The formulas allow technicians to make equipment decisions based on efficiency and savings. SEER and EER are used to calculate the amount of electricity a system will use while providing a specific amount of cooling. The map in figure 1 shown later in this lesson is broken down into cooling load hours. The map provides a realistic average of the hours per year an air conditioner will run in a specific region. A technician will use the SEER or EER of a system along with cooling load hours and cost of electricity to figure the average cost of operation.
A 36,000 Btu system with a SEER of 10.00 located in Baton Rouge, Louisiana, with an electrical rate of 7.5 cents per kwh (kilowatt hour).
Capacity (Btuh)/SEER X Cooling Load Hrs/1000 X Elec. Rate * Annual Cost of Operation
36000/10 X 2000/1000 X .075 * 3600 X 2 X .075 * $540.00
The capacity and SEER will be listed in the Air Conditioning and Refrigeration Institute (ARI) manual as shown on the SEER, HSPF table. The cooling load hours for the location of system can be found on figure 1 shown later in this lesson. The electric rate can be acquired from the local electric utility. The actual cost should include fuel adjustment charges and local taxes. The fuel adjustment may vary, but use the average for summer months. The annual cost of operation is the information every consumer needs to determine the amount of years a new system will take to pay for itself. This calculation can be used on several equipment choices to decide which combination is most cost effective.
**-*SEER Chart PDF.pdf*/-*
Use the previous example of a 3 ton, 10 SEER system compared to a 3 ton, 12.5 SEER system.
36000/12.5 X 2000/1000 X 0.75 * 3080 X 2 X .075 * $437.00
The 12.5 SEER system will cost $108.00 per year less to operate than the 10 SEER system. If the higher efficiency system cost $700.00 more, it is a better value. A system should pay for itself in ten or less years and has an average life of fifteen years. The better system would break even in 6-1/2 years and generate savings for another 8-1/2 years.
HSPF, COP and AFUE can be used in similar ways to determine cost effectiveness.
The amount of savings or lack of savings can be altered by the system being replaced, the quality of structure construction and the temperature maintained in the house. These figures are used for comparative shopping just as EPA mileage is used for car shopping.
As shown in the example , HSPF and SEER are used together to express energy efficiency in respective heating and cooling modes for ducted systems producing up to 65,000 Btus of cooling.
As shown in the example, EAR and COP are used together to express energy efficiency in respective heating and cooling loads.
Today it is comforting to know the environment can be preserved while saving money in operating cost. The following is a pictorial of an actual energy guide attached to air conditioning equipment. Note the range of EER.
**-*Energy guide hv-a6.gif*/-*
This energy guide used by permission of the Federal Trade Commission from Appendix K, page 212, of their Appliance Labeling Rule, 16 CFR Part 305, 1-1-92 Edition.
SEER and HSPF are based on heating and cooling seasons in Region IV (shown on Figure 1 and 2 maps below.)
Figures 1 and 2, Maps of Summer Cooling and Winter Heating Load Hours, are reprinted from pages 16 and 17 of the ARI Unitary Directory, August 1, 1992 - January 31, 1993, by courtesy of the Air-Conditioning and Refrigeration Institute, ARI.
Below is an explanation of the energy guide and ranges given for equipment.
**-*Energy guide hv-a8.gif*/-*
Energy Guide Top
This guide is designed to assist consumers in estimating their annual operating costs of central air conditioners and heat pumps covered by the U.S. Federal Trade Commission (FTC) appliance labeling rules. Along with the energy efficiency information contained in this directory, this guide is designed to assist consumers in making purchasing decisions. Contained in this guide are step-by-step instructions on how to perform the operating cost estimates. The operating cost estimates can be performed using data included in this directory. A sample worksheet is also provided.
Note. In the following text Energy Efficiency is expressed in 3 ways.
SEER, Seasonal Energy Effifiency Ratio (for cooling).
HSPF, Heating Seasonal Performance Factor (for heating).
EER, Energy Efficiency Rating (a term used by the Federal Trade Commission to mean either SEER or HSPF, whichever is applicable
To assist consumers in making informed decisions regarding equipment selection, the FTC has determined that the minimum and maximum product energy efficiency ratings available are those listed -
**-*EFR ranges table.pdf*/-*
Performance data for central air conditioners are shown in Section AC of the Directory. The cooling capacity and the SEER are listed for each single-package air conditioner and for each split-system combination of condensing (outdoor) unit and indoor coil.
Performance data for heat pumps are shown in section HP of the Directory. Capacities and efficiencies for cooling and heating are listed for each single-package heat pump and for each split-system combination of outdoor and indoor coil. Cooling and heating efficiencies are expressed in SEER and HSPF, respectively.
The Directory lists the average national annual operating cost for each air-conditioner in Section AC. It also lists the average national annual operating cost for cooling and for heating in Region IV (see map, fig.2) for each heat pump in Section HP.
Estimates of operating cost may be higher or lower than your average operating costs. They are affected by many factors that can vary widely. For example, since no two heating or cooling seasons are identical, operating costs will vary from year to year. Operating costs are also affected by the temperature that is to be maintained - the thermostat setting - with higher settings costing more in winter and lower settings costing more in summer. Other factors that affect system operation include the number of occupants, location within a region, activities that generate or release heat with the structure, and living habits such as the opening of windows, etc. Nevertheless, the estimates will be helpful in determining approximately how much a system will cost to operate and to compare to performance of different systems.
This explanation of the energy guide is reprinted from page 9 of the ARI Unitary Directory, August 1, 1992 - January 31, 1993, by courtesy of the Air-Conditioning and Refrigeration Institute, ARI.
The ARI (Air Conditioning and Refrigeration Institute) publishes a manual twice yearly that lists all central equipment available for sale in the USA. Listed are the SEER or HSPF values for each piece of equipment along with the SR and average annual operating cost. Note the range of SEER, HSPF and capacity when one condenser is matched with several indoor coils.
As shown, the lower the SEER or HSPF, the more the equipment costs to operate. The lower the SR number, the quieter the unit operates.
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Please indicate whether the following statements are true or false.
1._______ SEER is a ratio of Btuh to watts.
2._______ COP is a seasonally adjusted ratio of Btuh/watts X 3.412.
3._______ Louisiana is located in Region IV.
4._______ Because we have a longer cooling season than Philadelphia, PA, a 10.00 SEER unit would cost more to operate annually in our region. - Assume cost per kwh is the same.
5._______ A 12.00 SEER unit will cost more to operate than a 10.00 SEER unit.
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Given a heat pump with a capacity of 47,500 Btuh cooling and a SEER of 10.10 located in Lafayette, Louisiana, where the electric rate is 7.5 cents per kilowatt hour, calculate the annual operating cost in the cooling mode.
$____________ per year.
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Given a 12.50 SEER Heat Pump and 7.2 HSPF and SR 7.2 Bels, 10.98 EER, 6.80 COP at 47°F, calculate the following for region -
COP @ 47°- __________
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1. Locate Vermont (VT) on the maps in Figure 1 and Figure 2.
2. What is the heating region for VT ?
3. What are the cooling load hours for VT ?
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1. Locate Lafayette, LA on the maps in Figure 1 and Figure 2.
2. What is the heating region for Lafayette?
3. What the cooling load hours for Lafayette?
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Look at the ARI chart on (SEER, HSPF) and find the following information for model TWR048C outdoor unit and TXC060F5 indoor -
A. Capacity in (Mbtuh) _________________
B. SEER _______________
C. High temp capacity in (Mbtuh) _______________
D. HSPF _______________
E. Sound Rating _______________
F. Average annual cooling cost _______________
G. Average annual heating cost _______________
*-*'S - */-*
*-* TO ACTIVITY - */-*
*-* TO WORD - */-*
$705.45 per year
ANSWERS TO ACTIVITY -
SEER - 12.50
HSPF - 7.2
SR - 7.2
EER - 10.98
COP - 6.80
*-* TO ACTIVITY - */-*
1. Located in Northeast next to New York
3. Between 400 and 600 or an average of 500
*-* TO ACTIVITY -*/-*
1. Located in Southwest quadrant of Louisiana
2. Region II
3. 200 Cooling load hours.
*-* TO ACTIVITY - */-*
* Note to - notice the difference in average of activity 4 (part F) and the word problem.
Directory of Certified Unitary Air-Conditioners (Section AC), Unitary Air-Source Heat Pumps (Section HP) and Sound-Rated Outdoor Unitary Equipment. Air-Conditioning & Refrigeration Institute, Arlington, VA. 1992.
ANSI / ASHRAE 103-1988 ASHRAE STANDARD An American National Standard, Methods of Testing FOR ANNUAL FUEL UTILIZATION EFFICIENCY OF RESIDENTIAL CENTRAL FURNACES AND BOILERS. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Atlanta, GA. 1988.
By Todd Legere