Hvac tonnage chart

Step 1: Basic Info. In step one, the calculator will ask you to fill out basic info about your room, including its size, age, and type (bedroom, kitchen, office, etc.). This information will set the general parameters of your application. For example, knowing your building age helps the calculator understand the quality of insulation inside ...

Hvac tonnage chart. If your home or windows are older than 15 years and/or you live in an especially hot climate, you may need to go up as many as 53,500 BTUs/4.5 tons. You can use our AC size calculator above to find out what’s right for you. What Are BTUs for Air Conditioners? BTU stands for British Thermal Unit.

This calculator assists homeowners, HVAC professionals, and anyone in need of efficient temperature control. Formula: The tonnage of a heat pump is calculated based on the area of the space it needs to heat or cool. The formula for determining the required tonnage is as follows: Tonnage = (Area in square feet × Heating or Cooling Load factor ...

Easy To Use A/C Size Selection Tool: Check the color coded map above and confirm the zone your home is in. Then, on the chart included underneath, select the square footage of your home along with the zone you're in. From there you can select one of units that will be most efficient for your home. ZONE 1. ZONE 2. 1,000 - 1,200 sq. ft. small home, 3-4 bdrm apartment. 24,000 BTU. 1,400 - 1,500 sq. ft. medium home, 4-bdrm apartment. 30,000 BTU. 1500 - 1700 sq. ft. medium home, 4-bdrm apartment. Now, let’s discuss how this table will help you choose the right size air conditioner for the room or zone you want it to serve.Edited by M.J. Davis Lin , Brendan Klinkenberg and Lisa Chow. Original music by Diane Wong , Marion Lozano and Dan Powell. Engineered by Alyssa Moxley. Donald …Most homes need ACs that range from 18,000 to 60,000 BTUs. Sometimes you’ll see air conditioner size measured in tons instead of BTUs. Tonnage is just another way of expressing an air conditioner’s cooling performance. Below is an AC sizing chart to help you compare tonnage with BTU output: 1 ton = 12,000 BTUs.AC and Furnace Sizing Calculator for Free. If you are looking for a free AC System Calculator or HVAC Load Calculator, we have a free calculator to recommend to you. This free HVAC Sizing Calculator is full featured and allows you to print a complete heat gain and heat loss report. It is available at Black Belt Contracting.Next. Enter Room Size (in feet) Back. Next. Enter Area of Windows (in square feet) Back. Next. Is your floor Basement or Ground Floor First or Higher Floor.

This number is typically between 18 and 60. Divide this number by 12 (representing 12,000 BTU/hr, or one ton of cooling capacity) to get the overall tonnage of the unit. This chart may also be useful when converting the numbers: 18 = 1.5 tons. 24 = 2 tons. 30 = 2.5 tons. When it comes to optimal AC performance, size does matter. A unit that’s too small for your home will cause the system to run constantly and leave you with an ever-rising energy bill. If the system is too big, the air will be cooled quicker than the system can dehumidify the space. You’ll be left with a humid, sticky environment. Sizing systems. It’s important to install the right Trane matched system size for your home, depending on a number of factors. The wrong system size could cost you. A system that is too large will cool or heat your house quickly, but you still may not feel comfortable. It will satisfy the temperature setting on your thermostat before it can ...Calculation: 4 x 12,000 = 48,000 BTU. The case when you have BTUs and want to convert them to tons: Number of BTUs / 12,000 = Tons. Example: You have a 12,000 BTU portable air conditioner. Calculation: 12,000 / 12,000 = 1 ton. You have to convert BTU to tons in a number of situations regarding cooling and heating.Generally, a good rule of thumb is to allow for 20 BTUs (British Thermal Units) per square foot. Therefore, for a 2000 square foot area, a 40,000 BTU or 3.5-ton ...During the heating season, a BTU denotes how much warmth it can add to the room in that same hour. So, when we talk about an AC unit rated at 1, 2, or 3 tons, it just means the required amount of BTU needed. For example, a 3 ton air conditioning unit has 36,000 BTU/hr, and a 5-ton air conditioning unit has 60,000 BTU/hr.This audit will provide an estimate for the HVAC tonnage required for a given space. One ton of cooling capacity is equivalent to 12,000 BTUs per hour. A 3 ton AC unit can cool a space by 36,000 BTUs per hour, accommodating most moderately sized homes, while a 4 or 5 ton AC unit may be required for larger homes.29 Jun 2018 ... In laymen term, AC Tonnage is simply the cooling capacity or the cooling output of the air-conditioner. The calculation is quite simple. The ...

HVAC design tools include such popular items as the Trane Ductulator™, psychrometric charts, and load estimating forms. Learn more about the order process here . Ductulator - Hand held rotating calculator used for sizing supply and return duct systems using the equal friction design method.First, find the square footage of your room and then check its corresponding BTU requirements. This chart is only a starting point, though, and you should not base your purchase decision on this information alone. For a more precise estimate, you can use our HVAC sizing calculator. The most accurate method of sizing is with a professional …So, if you can figure out the BTUs of your HVAC system you can easily calculate the tonnage of your AC. Simply divide the BTUs by 12,000 to get tons. Sr. BTU. Ac. Tonnage. 1. 9,000. 3/4 Ton.One ton of cooling capacity is equal to 12,000 BTUh. Residential air conditioners usually range from 1.5 to 5 tons (or, 18,000 – 60,000 BTUh). Anything with ...AC Tonnage: It takes one ton of heat to remove 288,000 Btus from the air in a day. That’s the amount of Btus that must be removed to melt one ton of ice over 24 hours. Thus, a one-ton AC unit would be rated 12,000 Btus per hour. The total square feet in a home is the primary factor involved in calculating which AC is best.This AC BTU calculator is the first step in getting the right size central air conditioning system to make your home comfortable – the right temperature and perfect …

Little caesars oak hill wv.

Both offer a measurement of an air conditioner’s cooling ability over an hour’s time. One ton of cooling capacity is equal to 12,000 BTUh. Residential air conditioners usually range from 1.5 to 5 tons (or, 18,000 – 60,000 BTUh). Anything with larger cooling capacity would be considered light commercial. Tonnage ratings are typically ...The following tonnage chart gives you a rough idea of the correct AC tonnage or heat pump cooling ability needed to cool a home based on square footage. BTU to Tons …Air Conditioner Size Calculation · 0.5 If the highest temperature in summer exceeds 45 °c · 0.4 If the highest temperature in summer between 41- 45 °c · 0.3 If...BTU stands for British thermal unit, and there are 12,000 BTUs per one ton of AC capacity. Air conditioning units remove BTUs from the atmosphere. For example, if you see an air conditioning unit rated for two tons, it can remove 24,000 BTUs from the air. More tonnage equals a higher rating, which indicates a larger cooling capacity.48,000 BTUs. 2,500 square feet. 5 tons. 60,000 BTUs. 3,000 square feet. 6 tons. 72,000 BTUs. Once you know the appropriate number of BTUs required for your home's heat pump, you can start shopping ...

4 May 2023 ... Air Conditioning Sizing Chart ... As noted above, the size of your home is a major factor in making sure you get the right size AC unit. The most ...Dec 13, 2023 · The Chiller Tonnage Calculator is a vital tool used in the HVAC (Heating, Ventilation, and Air Conditioning) industry to determine the cooling capacity required for a particular system. It calculates the necessary tonnage of refrigeration needed to effectively cool a space or system based on specific inputs. This air conditioner size calculator, also known as an AC tonnage calculator, helps you choose the right size air conditioner for your room. It takes into account factors such as room size, city of use, number of people, and number of appliances in the room to recommend the appropriate AC size in tons. Use a tape measure to determine the length ...Tonnage: In reference to air conditioning, a ton measures how much heat removed by the system would be needed to melt 2,000 pounds, or one ton, of ice in a 24-hour period. The result is then expressed in BTUs per hour. According to the standard calculation, it takes 288,000 BTUs to melt a ton of ice in 24 hours, or 12,000 BTUs per hour.AN HVAC LOAD CALCULATOR THAT’S ACTUALLY FUN TO USE. For ages 8 to 80. How to perform an HVAC load calculation. Watch video. ... For example, a load calculation may call for a three-ton unit at 95-degree outdoor temperature, however, 97% of the time it is less than 95 degrees outdoors. A practical solution is to slightly undersize the unit but ...To really size the HVAC properly you have to do a heat load calc. Using xyx ton/sq ft would only get you into the realm of what size you have, ...AC Tonnage Calculator provided by: To schedule a professional tonnage calculation, call Gulf Coast Air Systems at 813-689-2082, or email us here >. Use our ac tonnage calculator to help you determine what size air conditioner …Apr 1, 2024 · The table on the right (or below if you’re viewing on a phone) shows the return duct size for HVAC unit from 1.5 tons to 5 tons. Based on 400 CFM per ton, the corresponding airflow is also provided. The next column is the diameter (in inch) for ROUND RIGID duct. The last column is the number of round rigid duct you need.

Next. Enter Room Size (in feet) Back. Next. Enter Area of Windows (in square feet) Back. Next. Is your floor Basement or Ground Floor First or Higher Floor.

Locate the second set of numbers within the larger M/N number (the numbers after the first dash, characters 6-8). This number indicates the BTUs/ hour of the unit. For example, 024 equals 24,000 BTUs. Divide the BTUs by 12,000 (one ton). This number will equal the tonnage of the AC unit. In this example, the unit is a two-ton unit (24,000 ... The HVAC size is 2.5 to 3 tons for the AC and 70,000 BTU for the furnace. That’s in Zone 4 – a zone with average temperatures. However, to get exact HVAC sizing for your home, fill out all the details in the calculator. Easy To Use A/C Size Selection Tool: Check the color coded map above and confirm the zone your home is in. Then, on the chart included underneath, select the square footage of your home along with the zone you're in. From there you can select one of units that will be most efficient for your home. ZONE 1. ZONE 2. AC Tonnage Chart. If you know the height of your room ceiling, you can get an even more accurate idea of the AC tonnage that you need with online AC tonnage calculators. It doesn’t even matter whether you’re looking for a window or split AC ton calculator. You can use any but this AC capacity calculator from Carrier is particularly useful:BTU stands for British thermal unit, and there are 12,000 BTUs per one ton of AC capacity. Air conditioning units remove BTUs from the atmosphere. For example, if you see an air conditioning unit rated for two tons, it can remove 24,000 BTUs from the air. More tonnage equals a higher rating, which indicates a larger cooling capacity.Divide 286,000 (amount of energy to melt a ton of ice), by 24 (hours in a day), the result is 11,917 BTU’s of energy per hour to melt the ton of ice. The industry rounded up to 12,000 Btu/h to reference 1-ton of air conditioner capacity. Therefore, a 2-ton A/C unit will remove 24,000 BTU’s of heat per hour; a 3-ton A/C unit will remove ...(Tonnage Per Square Foot) Simple answer: You need 0.0016 tons of AC per square foot. In short, if you’re looking to cool down a 600 sq ft area, you would need: AC …Visiting HVAC events and trade shows are one of the best way to equip yourself with the latest happenings in the air conditioning and refrigeration field. See the listing of events...To determine the tonnage of your Carrier AC unit, check the model number. The first two or three digits represent the nominal capacity in BTUs per hour. Divide this number by 12,000 to find the tonnage. For example, a model number with 24 as the first digits indicates a 2-ton unit.1. Calculate the CFM for Each Room. Most HVAC units are designed to have a 400 CFM of airflow for every 12000 BTU or 1 ton of cooling capacity and 12000 BTU divided by 400 CFM is 30. So, identify the BTU needed for each room and divide it by 30 to get the required CFM for the respective room.

Season unending.

Mike raahauge.

The equation for ‘ sq ft to BTU ‘ is quite simple – multiply the sq ft with 20. That means that a 500 sq ft room needs a 10,000 BTU air conditioner. Of course, do make sure to buy an AC unit that is a bit stronger if you have high ceilings, live in a hot climate, and have an above-average sun in those rooms.Koppel stresses the importance of choosing the right air conditioning size for your area not only to maximize the cooling efficiency of your unit but also to get the most value ... We have provided a simplified aircon size calculator to guide you in selecting the right size capacity for your area. Please fill in the fields below. 1. Enter Room ...Tonnage: In reference to air conditioning, a ton measures how much heat removed by the system would be needed to melt 2,000 pounds, or one ton, of ice in a 24-hour period. The result is then expressed in BTUs per hour. According to the standard calculation, it takes 288,000 BTUs to melt a ton of ice in 24 hours, or 12,000 BTUs per hour.This audit will provide an estimate for the HVAC tonnage required for a given space. One ton of cooling capacity is equivalent to 12,000 BTUs per hour. A 3 ton AC unit can cool a space by 36,000 BTUs per hour, accommodating most moderately sized homes, while a 4 or 5 ton AC unit may be required for larger homes. ... This BTU per square foot ...Divide the area by 600 to get the basic capacity. For example, if your room is 100 square feet: Basic capacity = 100 / 600 = 0.167 tons. Adjust for Number of ...1. Calculate the CFM for Each Room. Most HVAC units are designed to have a 400 CFM of airflow for every 12000 BTU or 1 ton of cooling capacity and 12000 BTU divided by 400 CFM is 30. So, identify the BTU needed for each room and divide it by 30 to get the required CFM for the respective room.Another term you will see used often for HVAC systems’ cooling capacities is “ton.” A ton equals 12,000 BTU, which would adequately cool about 500 square feet. We list BTU/tonnage where applicable for each system described below. The following chart is an estimation for tonnage coverage based on the square footage of your property.The HVAC size is 2.5 to 3 tons for the AC and 70,000 BTU for the furnace. That’s in Zone 4 – a zone with average temperatures. However, to get exact HVAC sizing for your home, fill out all the details in the calculator.Choosing the right sized air conditioner can be as easy as using a tape measure and a little mathematics. Simply measure the length and width of a room and figure the square footage. Let's say it is a 10 foot by 15-foot room. Multiply the two together to get 150 square foot room. Using the sizing chart to calculate the appropriate BTU … A water-chiller refrigeration ton is defined as: 1 Refrigeration Ton (RT) = 1 TONS cond = 12000 Btu /h = 200 Btu /min = 3025.9 k Calories /h = 12661 kJ/h = 3.517 kW . 1 kW = 0.2843 Refrigeration Ton (RT) A ton is the amount of heat removed by an air conditioning system that would melt 1 ton (2000 lbs.) of ice in 24 hours. Step 1: Basic Info. In step one, the calculator will ask you to fill out basic info about your room, including its size, age, and type (bedroom, kitchen, office, etc.). This information will set the general parameters of your application. For example, knowing your building age helps the calculator understand the quality of insulation inside ... ….

By dividing your square footage by 12,000, you can choose a 4 or 4.5-ton AC unit for a home over 2,500 square feet in size. Window air conditioning units typically have cooling capacities that ...An air conditioner generally needs about 20 BTU per square foot of living space. Once you've calculated the square footage of the room or home, multiply the result by 20 to find the air conditioner size for the home. For example, if the square footage of the home is 2,000 square feet, you can find the right air conditioner size by multiplying ... 2301 - 2700 sf. 5 Tons. 2401 - 3000 sf. 2501 - 3100 sf. 2601 - 3200 sf. 2751 - 3300 sf. 2701 - 3300 sf. Did you know that you can get big discounts on Goodman and Ruud air conditioning systems? Shop online or by phone and get FREE shipping. This air conditioner size calculator, also known as an AC tonnage calculator, helps you choose the right size air conditioner for your room. It takes into account factors such as room size, city of use, number of people, and number of appliances in the room to recommend the appropriate AC size in tons. Use a tape measure to determine the …Learn how to calculate the amount of AC tonnage required for a room with our Tonnage Calculator. Try it now and make a smart decision.If you are buying an HVAC system such as a window air conditioning unit or a mini split, the heating or cooling capacity is usually in BTUs. While smaller units use BTUs, big Home air conditioning units will often be rated in Tons, which can be confusing. ... HVAC BTU to TON Conversion Table Chart . BTU TON; 9,000: 3/4 TON: 12,000: 1 TON ...Elements in the AC Tonnage Chart. An understanding of the components that make up the tonnage chart will help you efficiently install the correct central air system. You will also gain an insight into what size central AC unit you need for your home or business, generating cost efficiencies in the long run.As a general rule, an air conditioner needs 20 Btu for each square foot of living space. But other considerations, such as the ceiling height and the size of your windows and doorways, might call ...The basic formula for determining the required tonnage of a central air conditioning system is as follows: ( ( House square footage times 30 then divided by 12,000 ) – 1.0 ) = Required Tonnage ... (such as 110 degrees in the desert) then don’t subtract 1 in the formula above. To determine a more accurate size for your region, use …Choosing the right sized air conditioner can be as easy as using a tape measure and a little mathematics. Simply measure the length and width of a room and figure the square footage. Let's say it is a 10 foot by 15-foot room. Multiply the two together to get 150 square foot room. Using the sizing chart to calculate the appropriate BTU … Hvac tonnage chart, Air Conditioner BTU Chart. The chart below is a great starting point for sizing your AC. These BTU calculations are based on a standard room with 8-foot ceilings, two windows and one door. If the room has more windows, doors or higher ceilings, adjust the BTUs upward. Other factors in determining the BTU size would be the room’s purpose., One ton of cooling capacity is equal to 12,000 BTUh. Residential air conditioners usually range from 1.5 to 5 tons (or, 18,000 – 60,000 BTUh). Anything with ..., There are 12,000 Btu's per ton. The number 24 in the model number indicates the unit is 24,000 Btu's, divided by 12,000 Btu's per ton, equals 2 tons. 24,000 Btu's/ 12,000 Btu's per ton = 2 tons. Use the following conversion information to determine your existing system size (use the system model number NOT the serial number) AC Direct Pricing., The line sizing charts on each case specification sheet can be used to size the subfeed branch lines. When the line serves one case. select the size specified for 50 equivalent feet for the 8’ or 12’ case. This may be as small as 5/8” (example service meat cases), or as large as 1-3/8” (example multi-shelf ice cream cases)., This AC BTU calculator is the first step in getting the right size central air conditioning system to make your home comfortable – the right temperature and perfect humidity. Central AC Sizes. AC capacity is measured in BTUs – actually BTU/hour, or the number of BTUs the unit moves in one hour of running., 2,200 CFM. 6 Ton Unit. 2,400 CFM. This chart is quite simple to read. Example: A 5-ton unit requires 2,000 CFM airflow. A 3-ton unit requires 1,200 CFM airflow. Now, it is important to understand when the 400 CFM per ton rule of thumb should not be applied. We will look at when the CFMs per BTU of cooling should be higher and lower:, Mr. Maloney said he was already paying $9,000 to $12,000 for a ton of premium cocoa, which he obtains from farmers around the world, particularly in Latin …, The HVAC systems analyzed in this calculator include (1) split systems/packaged A/C, (2) air cooled chilled water systems and (3) water cooled chilled water systems. This will help you to select equipment, space plan for any mechanical rooms and …, Apr 20, 2023 · An air conditioner generally needs about 20 BTU per square foot of living space. Once you've calculated the square footage of the room or home, multiply the result by 20 to find the air conditioner size for the home. For example, if the square footage of the home is 2,000 square feet, you can find the right air conditioner size by multiplying ... , This audit will provide an estimate for the HVAC tonnage required for a given space. One ton of cooling capacity is equivalent to 12,000 BTUs per hour. A 3 ton AC unit can cool a space by 36,000 BTUs per hour, accommodating most moderately sized homes, while a 4 or 5 ton AC unit may be required for larger homes. ... This BTU per square foot ..., At AL Naveed AC System Installation LLC, we use a complex formula and factor in many details to determine the exact amount of Btu your new air conditioner should have, we provide you with this free online Btu and Tonnage calculator (also known as load calculation) to give you a estimate. Just fill in your home or office square footage, the ..., The refrigeration calculator includes an advanced refrigeration system calculation method, based on component simulation rules proposed by ASHRAE, refrigerant properties calculated using NIST’s REFPROP, and updated thermodynamic correlations from different authors for the calculation of heat exchange., Sizing systems. It’s important to install the right Trane matched system size for your home, depending on a number of factors. The wrong system size could cost you. A system that is too large will cool or heat your house quickly, but you still may not feel comfortable. It will satisfy the temperature setting on your thermostat before it can ..., 13 Dec 2023 ... Under normal circumstances, the ideal room size for a 2 ton AC should be around 175 square feet to 250 square feet. But, again, a lot depends on ..., AC Tonnage Calculator accurately estimates the proper Central AC size in TONs & BTUs, as well as the cost to install your Central Air system in different climate zones, based on your house size & AC SEER rating, conditioned space size, heat load / loss, & other parameters. The size of your AC will determine the replacement costs & energy usage., Jan 5, 2024 · Air Conditioning Sizing Chart: 100 to 150 sq ft: 5,000 BTUs: 150 to 250 sq ft: 6,000 BTUs: ... For a 2,000-square-foot house, about 3 tons of air conditioning is best. Expect to need 40,000 BTU. , service technicians to demonstrate how to size refrigerant piping. Using This Guide This Guide covers R-22, R-407C, R-410A, and R-134a used in commercial air conditioning systems. It does not apply to industrial refrigeration and/or Variable RefrigerantVolume (VRV) systems. Illustrations and figures are not to scale., Tonnage = 60 ÷ 12. = 5. Answer: The Lennox air conditioning unit with model number HS26-60-1P has a tonnage of 5. Now that we found out that the tonnage is 5, we can also compute the area a 5-ton unit can cover. A 1-ton unit can cover an area of 600 square feet, or 20 BTU per square foot., A 1.5 ton AC covers how many square feet? Again, using the chart above, locate 1.5 Ton in the left column to find the answer. A 1.5 ton central AC, mini split or even a large window unit will effectively cool and dehumidify up to 825 square feet. AC Sizing Tip: It is crucial that you get the right size/capacity air conditioning system for your ..., To estimate the air conditioner size you'd need to cool a specific room: Measure the square footage or area in square meters of the room. For that, multiply its length by its width. If using meters, multiply the result by 0.092903. Multiply this by 25 BTU to get your air conditioner size., Step 1: Basic Info. In step one, the calculator will ask you to fill out basic info about your room, including its size, age, and type (bedroom, kitchen, office, etc.). This information will set the general parameters of your application. For example, knowing your building age helps the calculator understand the quality of insulation inside ..., This allows ample cooling, whether it is a rainy, moist day or a hot, sunny, humid day. Let’s say the room is 12 feet wide by 15 feet long. That means 12x15=180 square feet. Take the 180 sq. ft. times 25 BTU per square foot and you get the minimum BTU air conditioner you should buy. That means 180x25=4500 BTU cooling capacity is needed., A 1.5-ton AC is an ideal choice for a 900-square feet room. If you have the Carrier Comfort AC unit, it requires engine power of 7.07 horsepower to function at full speed. Meanwhile, its energy efficiency ranges from 14.0 to 16.5 SEER rating. With this rating, your AC consumes around $504 to $441 in electricity annually., If your home or windows are older than 15 years and/or you live in an especially hot climate, you may need to go up as many as 53,500 BTUs/4.5 tons. You …, This number is typically between 18 and 60. Divide this number by 12 (representing 12,000 BTU/hr, or one ton of cooling capacity) to get the overall tonnage of the unit. This chart may also be useful when converting the numbers: 18 = 1.5 tons. 24 = 2 tons. 30 = 2.5 tons. , Our free, easy-to-use HVAC load calculator will help you determine the necessary thermal output capacity (in BTUs) of any residential building., Calculate tonnage of heating and cooling equipment needed based on square footage of homes, such as 1 ton for every 1,000 square feet. Know the general rule of thumb for newer home..., HVAC Design and Engineering . This AC size calculator. This calculator is provided for use to calculate basic size in BTU to adequately cool a room of know size. The sizing chart below the calculator is useful to help you determine your approximate air conditioner size requirement in Tons. ALL calculators require a Premium Membership. Preview ..., This number is typically between 18 and 60. Divide this number by 12 (representing 12,000 BTU/hr, or one ton of cooling capacity) to get the overall tonnage of the unit. This chart may also be useful when converting the numbers: 18 = 1.5 tons. 24 = 2 tons. 30 = 2.5 tons., In case you know the power in watts but want to know how many BTUs it is equivalent to, you would only have to multiply the power in BTUs by 3.412. 1 Watt = 3.412 BTU/hour. You will often find that thermal power is expressed in kilowatts (kW). 1 kilowatt equals 1000 watts. Thus, an air conditioning system requiring 2322 W will be equivalent to ..., Simple; use the calculator or/and chart below, look up ‘5 kW’ and you will see that a 5 kW AC unit is basically a 1.42 Tons unit. Here is the conversion formula for kW to tons: 1 kW = 0.28434514 Tons. In short, 1 kW is equal to 0.28334514 tons. Basically, 3.5 kW is equal to 1 ton. You can use a hand calculator to calculate that., This AC BTU calculator is the first step in getting the right size central air conditioning system to make your home comfortable – the right temperature and perfect humidity. Central AC Sizes. AC capacity is measured in BTUs – actually BTU/hour, or the number of BTUs the unit moves in one hour of running., How To Calculate Return Duct Size. Here is the step-by-step guide you can use (the all-encompassing chart is below the guide): Multiply the tonnage of your HVAC unit by 400 to get the CFMs.Example: 3-ton unit will require 3 × 400 CFM = 1,200 CFM airflow. Specify the shape of the ducts you are using: Return ducts can be either round or rectangular.; …