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# 59446885 hvac

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### 59446885 hvac

2. 2. b Values are based on standard rating conditions specified in ARI Standard 550/590-98. Only packaged chillers (i.e., none with remote condensers) are covered. • So the easy method is; •••• calculate the room volume, length times width times ceiling height, •••• divide room volume by 10 by shifting the decimal point one place to the left, •••• get the size machine your room really needs (for 6 changes hourly), in cubic feet per minute. ____________________________________________________________________________________ STEP 1 - Calculate the volume of the area to be cleaned in cubic feet. Length x Width x Height of area = Cubic Volume STEP 2 - Divide the volume by 60 which represents minutes/hour. Volume of Area ÷ 60 minutes in an hour = Cubic Feet Per Required for ONE AIR CHANGE/HOUR STEP 3 - Multiply the number of cfm's required in step #2 by the number of air changes desired from the chart above. Cubic Feet per Minute (#2) x #of Air Changes/hour (from chart above) = Cubic Feet per Minute (CFM) required for this application STEP 4 - Compare the Cubic Feet per Minute (CFM) required with the cfm rating of the units you are considering. If the cfm required is more than any of the cfm ratings on an individual unit, you will need more than one unit for that application. CFM required for One Air Change/Hour x Air Changes/Hour Needed = CFM's Needed for Your Application For a faxed or mailed quotation, please send us the measurements of the area you wish to clean and the number of air changes/hour you wish to accomplish. We'll do the work for you...just send us an e-mail. EXAMPLE SPACE CALCULATION Room dimensions: 50' x 100' x 10' ceiling Type of area: Restaurant or Lounge Air Changes Desired: 16 Air Changes/Hour (heavy pollution level) Step 1 - Volume 50' x 100' x 10' = 50,000 cubic feet Step 2 - Find Out CFM Required for One Air Change/Hour
3. 3. 50,000 Cu. Ft.÷ 60 Minutes in an Hour = 833 cubic feet/Minute = ONE Air Change in an Hour Step 3 - Total Volume Per Minute To Be Cleaned 833cfm x 16 air changes = 13,328 cfm Step 4 - Number of Units Needed 13,328 cfm ÷ cfm of chosen unit = Number of Units Needed (Model LA-2000): 13,328 cfm ÷ 2,100 cfm = 6.34 or 6-7 units (Model LA-1400): 13,333 cfm ÷ 1,100 cfm = 12.09 or 12-13 units The recommended ventilation rate for homes is 0.35 air changes per hour (ACH) or 15 cubic feet per minute per person. For example, a 1,200 square foot home with 8-foot walls has an air volume of 9,600 cubic feet. Obtaining an air changeof 0.35 per hour requires exchanging 0.35 x 9,600 = 3,360 cubic feet of air per hour. This is an airflow rate of 3,360 ÷ 60 minutes per hour = 56cubic feet per minute. Millions of people spend 90% of their day inside, so it's important that the buildings they occupy have a substantial amount of fresh, outside air. ASHRAE 62 ventilation standards recommend that 15 to 60 cubic feet per minute (CFM) of outside air should be supplied for every person within a building. Although this is just a recommendation, Total Volume of Air in the Room ÷ 5 = Minimum Recommended CFM The "magic number 5" in this formula is based on 12 changes per hour, divided by 60 minutes/hour to give us the number of changes per minute. To apply this to your bathroom, multiply the width by the length by the height to determine the total cubic feet... Width x Length x Height = 6ft. x 8ft. x8ft. = 384 cubic feet Divide the volume of your bathroom by 5 to find out the recommended CFM... 384 cubic feet ÷ 5 = 76.8 CFM or Cubic Feet per Minute The first step when sizing for a ventilating fan is to determine the application. Decide whether you are sizing for intermittent or continuous ventilation (see pages 6 and 7). If intermittent, determine which application, (i.e. bathroom, kitchen or other). Use the following industry recommendations to determine Air Changes per Hour (ACH) for your specific application. Intermittent (spot) ventilation: The Home Ventilating Institute (HVI) recommends the following Air Changes per Hour (ACH). I. Bathrooms - 8 ACH or 1 CFM/sq ft II. Kitchens - 15 ACH or 2 CFM/sq ft Other Rooms - 6 ACH or .75 CFM/sq ft Continuous (Whole House) Ventilation: Most building codes have adopted the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) Standard 62. The most current version, ASHRAE 62.2-2004, calls for continuous mechanical ventilation as shown below.
4. 4. I. House or apartment - 7.5 CFM per person plus 1 CFM per 100 square feet To calculate how many CFM of airflow is required to properly ventilate any room in your home, use the following calculation. • For an 8 foot ceiling take the square footage of the room and multiply it by 1.1. (Example – 10' x 10' room with 8' ceilings: 10' x 10' = 100 square feet x 1.1 = 110 CFM’s) • For any ceiling over 8 feet, take the height of the ceiling and multiply by .1375. Take this figure and multiply by the square footage of the room. This will equal the recommended CFMs. (Example – 10' x 12' room with 9' ceilings: 9' x .1375 =1.24 x 120 square feet = 149 CFMs.) What does air change mean? One air change occurs in a room when a quantity of air equal to the volume of the room is supplied and/or exhausted. Air change rates are units of ventilation that compare the amount of air moving through a space to the volume of the space. Air change rates are calculated to determine how well a space is ventilated compared to published standards, codes, or recommendations. Air changes per hour (ACH) is the most common unit used. This is the volume of air (usually expressed in cubic feet) exhausted or supplied every hour divided by the room volume (also usually expressed in cubic feet). Airflow is usually measured in cubic feet per minute (CFM). This is multiplied by 60 minutes to determine the volume of air delivered per hour (in cubic feet). To calculate room volume (in cubic feet), multiply room height (in feet) by the room area (in square feet). Room area is the room width (in feet) times the room length (in feet). ACH = airflow per hour = CFM X 60 minutes room volume cubic feet A room may have two airflow values, one for supply and another for exhaust. (The airflow difference between these two values is called the offset.) To calculate the air change rate, use the greater of the two airflow values. Example of air change per hour calculation An isolation room is 200 square feet in area and has a ceiling height of 9 feet. Airflow measurements indicate a supply airflow of 360 CFM and an exhaust airflow of 480 CFM. Does this room comply with the CDC recommendation that isolation rooms have a minimum airflow rate:of 12 ACH for new construction? Air change rate: 480 CFM X 60 = 16 ACH 200 ft2 X 9 ft Exhaust air offset: 480 CFM – 360 CFM = 120 CFM In conclusion, this room exceeds the CDC minimum requirement. The offset of 120 CFM is made up by air from outside the room. This information Useful Formulas: • Total Heat (BTU/hr) = 4.5 x cfm x ∆h (std. air) • Sensible Heat (BTU/hr) = 1.1 x cfm x ∆t • Latent Heat (BTU/hr) = 0.69 x cfm x ∆gr. (std. air)
5. 5. • Total Heat (BTU/hr) = 500 x gpm x ∆t (water) • BTU/hr = 3.413 x watts = HP x 2546 = Kg Cal x 3.97 • TONS = 24 x gpm x ∆t (water) • GPM cooler = (24 x TONS) / ∆t (water) • Fluid Mixture Tm = (Xt1 + Yt2) / X + Y (this works for air or water) • Lb. = 453.6 grams = 7000 grains • psi = ft. water/2.31 = in. hg/2.03 = in. water/27.7 = 0.145 x kPa • Ton = 12,000 BTU/hr = 0.2843 x KW • HP (air) = cfm x ∆p (in.H2O)/6350 x Eff. • HP (water) = gpm x ∆p (ft.)/3960 x Eff. • Gal. = FT 3 /7.48 = 3.785 Liters = 8.33 lb. (water) = 231 in. 3 • gpm= 15.85xL/S • cfm = 2.119 x L/S • Liter = 3.785 x gal = 0.946 x quart = 28.32 x ft 3 • Therm = 100,000 BTU = MJ/105.5 • Watt/sq. ft. = 0.0926 x W/M 2 • yd. = 1.094 x M • ft. = 3.281 x M • ft 2 = 10.76 x M 2 • ft 3 = 35.31 x M 3 • ft/min = 196.9 x M/S • PPM (by mass) = mg/kg Definitions A BTU is defined as the amount of heat required to raise the temperature of one pound of liquid water by one degree Fahrenheit. As is the case with the calorie, several different definitions of the BTU exist, which are based on different water temperatures and therefore vary by up to 0.5%: Conversions One BTU is approximately: 1 054 – 1 060 J (joules) 252 – 253 cal (calories) 25 031 – 25 160 ft·pdl (foot-poundal) 778 – 782 ft·lbf (foot-pounds-force) Other conversions: In natural gas, by convention 1 MMBtu (1 million BTU, sometimes written "mmBTU") = 1.054615 GJ. Conversely, 1 gigajoule is equivalent to 26.8 m3 of natural gas at defined temperature and pressure. So, 1 MMBtu = 28.263682 m3 of natural gas at defined temperature and pressure. 1 standard cubic foot of natural gas yields ≈ 1030 BTU (between 1010 BTU and 1070 BTU, depending on quality when burned)  Associated units
7. 7. an architect or qualified environmental engineer to design an HVAC system for your specific requirements. Heating Heater sizing formula – 7 watts of heat per square foot of floor space Example: 10’ x 20’ room = 200 square feet 200 sq. ft. x 7 = 1400 watts of heat required (Note: 1 watt = approximately 3.4 BTU’s) Ventilation The ventilation required within a room depends on a couple of factors: 1) Occupancy -- the number of people normally in the room; and 2) Usage – lunchrooms or conference rooms may require more ventilation. General rule of thumb – changing the air in the room every 10 minutes is sufficient Example: 10’ x 20’ room with 8’ ceiling height = 10’x20’x8’ = (1600 cubic feet) 1600 cu. ft. / 10 minutes = 160 cu. ft. per minute (CFM); therefore, A 160 CFM fan should be adequate for this room. Note: If smoking is allow in the room, the air should be changed every three minutes. Air Conditioning Air conditioner sizing formula – 30 BTU’s of cooling per square foot of floor space Example: 10’ x 20’ room = 200 square feet 200 sq. ft. x 30 BTU’s = 6,000 BTU’s of cooling required If the room is going to be heavily occupied (i.e. lunchroom, conference room) or located near a heat producing piece of equipment, the amount of air conditioning should be increased. A good rule of thumb is to add 500 BTU’s for each person in the room. Material extracted in whole or in part with permission and courtesy of Starrco. Updated June 2007 CALCULATING COOLING CAPACITY A good rule of thumb to estimate the amount of cooling capacity you need is to multiply the area of floor space (ft2) by a factor of 10 and add 3,000. For example, the amount of cooling capacity for a 20-foot by 20-foot room would be: [400 ft2 x 10] + 3,000 = 7,000 Btu/hour
8. 8. ENGINEERING DATA 1 ton a/c = 12,000 BTU per hour 1 Boiler HP = 42,000 BTU input (@ approx. 80% efficiency) 100 Boiler HP = 42 therm Input (@ approx. 80% efficiency) 100 lb Steam = 1 therm (approx.) 1 Engine HP = 10,000 BTU input (approx.) 1 British Thermal Unit = Energy required to raise the temperature of 1 lb. Mass of water by 1° F 1 SCF natural gas = 1,000 BTU (approx.) 100 SCF natural gas = 1 therm (approx.) 1 MSCF natural gas = 1,000 scf 1 MSCF = 10 therm 1 Therm = 29.3 kilowatt hr Standard Cubic Foot = Volume of gas at standard conditions Standard conditions = 60° F @ 14.73 psia SCFH = Volume flow rate per hour @ standard conditions Degrees Celsius = 5/9 ( °F - 32) ABBREVIATIONS ACSH - actual cubic feet per hour ACFM - actual cubic feet per minute BTU - British thermal unit MSCF - (thousand) standard cubic feet N.O. - Normally open N.C. - Normally closed PSI - pounds per square inch PSIA - pounds per square inch absolute PSIG - pounds per square inch gauge SCFH - Standard cubic feet per hour w.c. - inches of water column G - Gravity H - Pressure drop Q - Flow T - Temperature W - Flow rate RULES OF THUMB - UNIT SIZING Sizing Boiler Feed or Condensate Return ump Discharge Pressure: 1) If boiler < 50 psig, size pump to discharge 5 psig above working pressure. 2) If boiler > psig, size pump to discharge 10 psig above working pressure. Sizing Boiler Feed or Condensate Return Pump Capacity: 1) Condensate pump = 2 x condensate return rate 2) Boiler Feed pump = 2 x boiler evaporation rate, or: a) .14 GPM/BHP (on/off pumps) b) .104 GPM/BHP (continuous running pumps) Receiver Storage: 1) Size condensate receivers for 2 minute net storage capacity per return rate. 2) Size boiler feed receivers for system capacity (normally estimated at 10 minutes) RULES OF THUMB - GENERAL 1 Ft3 Natural Gas = 1000 BTU 1 Therm Natural Gas = 100,000 BTU
9. 9. 1 Unit Natural Gas = 10 Therms = 1,000,000 BTU 1 Ft3 Propane = 2,500 BTU 1 Gallon #2 Oil - 140,000 BTU 1 lb. Steam = 1000 BTU 1 BHP = 42,000 BTU / hr Input 1 BHP = 33,600 BTU / hr Output 1 KWH Electric = 3412 BTU Normal Stack Temp on a 15 psig Steam Boiler = 375°F Normal Stack Temp on a 150 psig Steam Boiler = 475°F Normal Stack Temp on a 30 psig Hot Water Boiler = 340°F 1 psig = 2.31' Head 1 psig = 27.68" H20 Air Supply Required (in CFM) = 10.8 X BHP Louver Size = 1 In2 per 4000 BTU (Input) HVAC Heating, ventilating, and air conditioning is based on the basic principles of thermodynamics, fluid mechanics, and heat transfer, and to inventions and discoveries made by Michael Faraday, Willis Carrier, Reuben Trane, James Joule, William Rankine, Sadi Carnot, and many others. The invention of the components of HVAC systems goes hand-in-hand with the industrial revolution, and new methods of modernization, higher efficiency, and system control are constantly introduced by companies and inventors all over the world. The three functions of heating, ventilating, and air-conditioning are closely interrelated. All seek to provide thermal comfort, acceptable indoor air quality, and reasonable installation, operation, and maintenance costs. HVAC systems can provide ventilation, reduce air infiltration, and maintain pressure relationships between spaces. How air is delivered to, and removed from spaces is known as room air distribution.[1] 10.8 Air-Conditioning 10.8.1 Air-conditioning is the application of methods for controlling the temperature of internal environments for the purpose of: (a) promoting human health and comfort, (b) improving working efficiency, (c) maintaining materials in the most suitable conditions for storage and manufacturing operations, and (d) supplying conditioned air (hot or cold) for industrial process. Multistoreyed office, hotel and other buildings are air- conditioned to increase working efficiency and to provide optimum thermal comfort of the occupants. Thermal comfort depends on proper combination of dry bulb temperature, relative humidity and air velocity. Air Change per Hour (ACH) :- The number of times per hour that the volume of a specific room or building is supplied or removed from that space by mechanical and natural ventilation. Air handler, or air handling unit (AHU) :- Central unit consisting of a blower, heating and cooling elements, filter racks or chamber, dampers, humidifier, and other central equipment in direct contact with the airflow. This does not include the ductwork through the building. British thermal unit (BTU) :- Any of several units of energy (heat) in the HVAC industry, each slightly more than 1 kJ. One BTU is the energy required to raise one pound of water one degree Fahrenheit, but the many different types of BTU are based on different interpretations of this “definition”. In the United States the power of HVAC systems (the rate of cooling and dehumidifying or heating) is sometimes expressed in BTU/hour instead of watts.
10. 10. Chiller :- A device that removes heat from a liquid via a vapor-compression or absorption refrigeration cycle. This cooled liquid flows through pipes in a building and passes through coils in air handlers, fan-coil units, or other systems, cooling and usually dehumidifying the air in the building. Chillers are of two types; air-cooled or water-cooled. Air-cooled chillers are usually outside and consist of condenser coils cooled by fan-driven air. Water-cooled chillers are usually inside a building, and heat from these chillers is carried by recirculating water to outdoor cooling towers. Coil :- Equipment that performs heat transfer when mounted inside an Air Handling unit or ductwork. It is heated or cooled by electrical means or by circulating liquid or steam within it. Air flowing across it is heated or cooled. Controller :- A device that controls the operation of part or all of a system. It may simply turn a device on and off, or it may more subtly modulate burners, compressors, pumps, valves, fans, dampers, and the like. Most controllers are automatic but have user input such as temperature set points, e.g. a thermostat. Controls may be analog, or digital, or pneumatic, or a combination of these. delta T :- delta T is a reference to a temperature difference. It is used to describe the difference in temperature of a heating or cooling fluid as it enters and as it leaves a heat transfer device. This term is used in the calculation of coil efficiency. Fan-coil unit (FCU) :-A small terminal unit that is often composed of only a blower and a heating and/or cooling coil (heat exchanger), as is often used in hotels, condominiums, or apartments. Condenser :- A component in the basic refrigeration cycle that ejects or removes heat from the system. The condenser is the hot side of an air conditioner or heat pump. Condensers are heat exchangers, and can transfer heat to air or to an intermediate fluid (such as water or an aqueous solution of ethylene glycol) to carry heat to a distant sink, such as ground (earth sink), a body of water, or air (as with cooling towers). Constant air volume (CAV) :- A system designed to provide a constant air volume per unit time. This term is applied to HVAC systems that have variable supply-air temperature but constant air flow rates. Most residential forced-air systems are small CAV systems with on/off control. Damper : - A plate or gate placed in a duct to control air flow by introducing a constriction in the duct. Evaporator : - A component in the basic refrigeration cycle that absorbs or adds heat to the system. Evaporators can be used to absorb heat from air (by reducing temperature and by removing water) or from a liquid. The evaporator is the cold side of an air conditioner or heat pump. Furnace : - A component of an HVAC system that adds heat to air or an intermediate fluid by burning fuel (natural gas, oil, propane, butane, or other flammable substances) in a heat exchanger. Fresh air intake (FAI) :- An opening through which outside air is drawn into the building. This may be to replace air in the building that has been exhausted by the ventilation system, or to provide fresh air for combustion of fuel. Grille : -A facing across a duct opening, usually rectangular is shape, containing multiple parallel slots through which air may be delivered or withdrawn from a ventilated space.
11. 11. Heat load, heat loss, or heat gain :- Terms for the amount of heating (heat loss) or cooling (heat gain) needed to maintain desired temperatures and humidities in controlled air. Regardless of how well-insulated and sealed a building is, buildings gain heat from warm air or sunlight or lose heat to cold air and by radiation. Engineers use a heat load calculation to determine the HVAC needs of the space being cooled or heated. Louvers : - Blades, sometimes adjustable, placed in ducts or duct entries to control the volume of air flow. The term may also refer to blades in a rectangular frame placed in doors or walls to permit the movement of air. Makeup air unit (MAU) :- An air handler that conditions 100% outside air. MAUs are typically used in industrial or commercial settings, or in once- through (blower sections that only blow air one-way into the building), low flow (air handling systems that blow air at a low flow rate), or primary-secondary (air handling systems that have an air handler or rooftop unit connected to an add-on makeup unit or hood) commercial HVAC systems. Packaged terminal air conditioner (PTAC) : - An air conditioner and heater combined into a single, electrically-powered unit, typically installed through a wall and often found in hotels. Roof-top unit (RTU) : -An air-handling unit, defined as either "recirculating" or "once-through" design, made specifically for outdoor installation. They most often include, internally, their own heating and cooling devices. RTUs are very common in some regions, particularly in single-story commercial buildings. Variable air volume (VAV) system : - An HVAC system that has a stable supply-air temperature, and varies the air flow rate to meet the temperature requirements. Compared to CAV systems, these systems waste less energy through unnecessarily-high fan speeds. Most new commercial buildings have VAV systems. The most common units for heat are • BTU - British Thermal Unit • Calorie • Joule BTU - British Thermal Unit: - The unit of heat in the imperial system - the BTU - is • the amount of heat required to raise the temperature of one pound of water through 1o F (58.5o F - 59.5o F) at sea level (30 inches of mercury). • 1 Btu (British thermal unit) = 1055.06 J = 107.6 kpm = 2.931 10-4 kWh = 0.252 kcal = 778.16 ft.lbf = 1.0551010 ergs = 252 cal = 0.293 watt-hours An item using one kilowatt-hour of electricity will generate 3412 BTU. Calorie: - A calorie is • the amount of heat required to raise the temperature of one gram of water 1o C. • 1 kcal = 4186.8 J = 426.9 kp.m = 1.163 10-3 kWh = 3.088 ft.lbf = 3.9683 Btu = 1000 cal The calorie is outdated and commonly replaced by the SI-unit Joule. Joule: - The unit of heat in the SI-system the Joule is
12. 12. • the mechanical energy which must be expended to raise the temperature of a unit weight (2 kg) of water from 0o C to 1o C, or from 32o F to 33.8o F. • 1 J (Joule) = 0.1020 kpm = 2.778 10-7 kWh = 2.389 10-4 kcal = 0.7376 ft.lbf = 1 kg.m2 /s2 = 1 watt second = 1 Nm = 1 ft.lb = 9.478 10-4 Btu Chiller Refrigeration Tons A chiller refrigeration ton is defined as: 1 refrigeration ton = 12,000 Btu/h = 3,025.9 k Calories/h A ton is the amount of heat removed by an air conditioning system that would melt 1 ton of ice in 24 hours. Cooling Tower Tons A cooling tower ton is defined as: 1 cooling tower ton = 15,000 Btu/h = 3,782 k Calories/h Heat Load and Water Flow A water systems heat load in Btu/h can be simplified to: h = cp ρ q dt = 1 (Btu/lbm o F) 8.33 (lbm/gal) q (gal/min) 60 (min/h) dt (o F) = 500 q dt (1) where h = heat load (Btu/h) cp = 1 (Btu/lbm o F) for water ρ = 8.33 (lbm/gal) for water q = water volume flow rate (gal/min) dt = temperature difference (o F) Example - Water Chiller Cooling Water flows with 1 gal/min and 10o F temperature difference. The ton of cooling load can be calculated as: Cooling load = 500 (1 gal/min) (10o F) / 12,000 = 0.42 ton The efficiency of chillers depends on the energy consumed. Absorption chillers are rated in fuel consumption per ton cooling. Electric motor driven chillers are rated in kilowatts per ton cooling. KW/ton = 12 / EER KW/ton = 12 / (COP x 3.412)
13. 13. COP = EER / 3.412 COP = 12 / (KW/ton) / 3.412 EER = 12 / KW/ton EER = COP x 3.412 If a chillers efficiency is rated at 1 KW/ton, the COP=3.5 and the EER=12 Cooling Load in - kW/ton The term kW/ton is common used for large commercial and industrial air-conditioning, heat pump and refrigeration systems. The term is defined as the ratio of the rate of energy consumption in kW to the rate of heat removal in tons at the rated condition. The lower the kW/ton the more efficient the system. kW/ton = Pc / Er (1) where Pc = energy consumption (kW) Er = heat removed (ton) Coefficient of Performance - COP The Coefficient of Performance - COP - is the basic unit less parameter used to report the efficiency of refrigerant based systems. The Coefficient of Performance - COP - is the ratio between useful energy acquired and energy applied and can be expressed as: COP = Eu / Ea (2) where COP = coefficient of performance Eu = useful energy acquired (btu in imperial units) Ea = energy applied (btu in imperial units) COP can be used to define both cooling efficiency or heating efficiency as for a heat pump.
14. 14. • For cooling, COP is defined as the ratio of the rate of heat removal to the rate of energy input to the compressor. • For heating, COP is defined as the ratio of rate of heat delivered to the rate of energy input to the compressor. COP can be used to define the efficiency at a single standard or non-standard rated condition or a weighted average seasonal condition. The term may or may not include the energy consumption of auxiliary systems such as indoor or outdoor fans, chilled water pumps, or cooling tower systems. For purposes of comparison, the higher the COP the more efficient the system. COP can be treated as an efficiency where COP of 2.00 = 200% efficient For unitary heat pumps, ratings at two standard outdoor temperatures of 47o F and 17o F (8.3o C and -8.3o C) are typically used. Energy Efficiency Ratio - EER The Energy Efficiency Ratio - EER - is a term generally used to define the cooling efficiency of unitary air-conditioning and heat pump systems. The efficiency is determined at a single rated condition specified by the appropriate equipment standard and is defined as the ratio of net cooling capacity - or heat removed in Btu/h - to the total input rate of electric energy applied - in watt hour. The units of EER are Btu/w.h. EER = Ec / Pa (3) where EER = energy efficient ratio (Btu/W.h) Ec = net cooling capacity (Btu/h) Pa = applied energy (Watts) This efficiency term typically includes the energy requirement of auxiliary systems such as the indoor and outdoor fans and the higher the EER the more efficient is the system. Definitions A BTU is defined as the amount of heat required to raise the temperature of one pound of liquid water by one degree Fahrenheit. As is the case with the calorie, several different definitions of the BTU exist, which are based on different water temperatures and therefore vary by up to 0.5%: Conversions One BTU is approximately: 1 054 – 1 060 J (joules)