How Do You Know How Many Btus You Need

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The British Thermal Unit of measurement (BTU) is the bones measure of heat energy in the Regal system. Ane BTU is defined as the amount of heat necessary to raise 1 pound (0.45 kg) of h2o 1F. Furnaces are rated based upon how much thermal heat they can produce per hr (BTU/h), while air conditioners are rated based upon how much thermal heat they can remove per hour (BTU/h). Choosing a furnace or air conditioning system with the right number of BTUs per foursquare human foot of infinite can help you oestrus or cool your habitation efficiently and toll-effectively.

1. i

   Measure the square footage of your entire dwelling. If you're installing a furnace, observe the foursquare footage of each room in your home and add them together. This will give you the full square footage of your space and so you can choose a furnace that will fairly heat your habitation.^[ane]

   • For a rectangular room, multiply the length and width, measured in anxiety.
   • For a triangular room, multiply the length and width, then divide by two.
   • For a round room, measure out the radius ("r" which is the distance from the center to the edge). Plug the radius into the following equation, using three.xiv for π: πr²
   • For rooms with odd shapes, divide them into regular shapes and measure each shape separately.

2. 2

   Find out which climate zone you live in to determine the heating factor. Await for a climate zone map online and figure out which zone you live in to help you lot determine the heating gene, or the number of BTUs you lot need per square foot to adequately oestrus your home. In general, the further from the equator you alive, the greater the number of BTUs you'll need.^[2]

   The heating factor in BTUs per square pes for each zone is equally follows:
   Zone 1: 30-35
   Zone 2: 35-xl
   Zone 3: 40-45
   Zone 4: 45-50
   Zone 5: fifty-55

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3. 3

   Multiply your square footage by the heating factor for your zone. All you have to do to find out what capacity furnace is best for your home based on its location is to multiply the foursquare footage of the space by the heating factor.^[3]

   • For instance, if you alive in Zone 2 and have a i,200-square-foot domicile, multiply ane,200 by 35-twoscore to get a BTU range of 42,000-48,000.

4. 4

   Employ the lower end of the range if your abode is well insulated or the higher end if information technology's non. Improve insulated homes need fewer BTUs per hour per square human foot than older homes. If your home is new or well insulated, yous can use the lower of the ii numbers for your climate zone; if it is older or poorly insulated, use the college number of the range.^[4]

   • Say that you live in a brand new home in Zone one. Multiply your square footage by 30 BTUs to notice out what capacity furnace you need. Alternatively, if you live in an older home in Zone 6, multiply your square footage by sixty BTUs to ensure you purchase a furnace with enough capacity to rut the space.
   • Note that newer homes tend to exist improve insulated than older homes because of revisions to building codes over the years.

5. 5

   Take the efficiency rating of the furnace into account. Furnaces are rated not past the actual BTU output you receive only by the amount of heat they generate. How much of the oestrus a furnace generates (input estrus) that actually reaches y'all (output heat) is a measure of how efficient the furnace is. The efficiency is expressed in percentage as a ratio of the output to input heat. Most modern furnaces are rated equally either 80 or 90% efficient.^[five]

   • For instance, a 100,000 BTU/h input furnace would not be plenty to heat a home needing an output of 100,000 BTUs per 60 minutes. An 80% efficient furnace would evangelize an output of merely 80,000 BTU/h (100,000 x 0.8). To discover an 80% efficient furnace that does provide enough ability, divide the BTU/h rating y'all need by 0.eight. And then, 100,000 BTU/h ÷ 0.8 = 125,000 BTU/h, pregnant yous'd demand a furnace rated to 125,000 BTU/h input.

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1. 1

   Measure the foursquare footage of the space yous plan to cool. If you want to install a central air-conditioning unit of measurement, measure the square footage of each room and add all of the numbers together to notice the total square footage of your abode. Alternatively, if you're just going to install an A/C unit to cool a single room, find the square footage of that room.^[6]

   • Multiply the length by the width, in feet, to find the foursquare footage of a rectangular room.
   • Multiply the length and width of a triangular room, then carve up that number by 2 for a triangular room.
   • Mensurate the radius of a circular room ("r" which is the altitude from the heart to the edge), foursquare the number, then multiply that by π (3.fourteen) (the formula is: πrⁱⁱ).
   • Divide rooms with odd shapes or alcoves into regular shapes and measure each shape separately.

2. 2

   Multiply your square footage by xx BTUs to get a full general judge. Typically, programme to purchase a heating or cooling unit of measurement with 20 BTUs for every foursquare foot of space yous have. However, keep in mind that factors such as your climate zone, sun exposure, and the number of people living in your home may require y'all to adjust this effigy.^[7]

   • For instance, if you live in a home that'southward 800 square feet, you'll need a unit with sixteen,000 BTUs. On the other mitt, if y'all live in a 5,000-square-foot dwelling, get a unit with 100,000 BTUs.

3. 3

   Select an A/C unit of measurement with a lower chapters if you lot don't have a lot of sun exposure. The position of your home likewise affects how many BTUs y'all need to properly heat or cool information technology. Reduce the capacity by 10% if your home or room gets a lot of shade, or increment the capacity past 10% if your abode or room is commonly in the sunshine.^[8]

   • Take a look at your sun exposure during the middle of the day in the summertime season to help you gauge this accurately.

4. 4

   Increase the chapters if more than 2 people live in your home. If you lot take a lot of family members, you'll need an air conditioner that has a college chapters. Add 600 BTUs per person for a family unit of more than 2.^[9]

   • For instance, if there are 6 people living in your dwelling house, multiply 600 by four to get 2,400. Add together ii,400 BTUs to the number you calculated by multiplying your square footage by 20 to ensure your unit volition cool your space well.

5. 5

   Get a organization with more BTUs if it will be in the kitchen. Kitchens have lots of appliances that requite off rut, including stoves and dishwashers. If you're installing an A/C unit in your kitchen, select ane with 4,000 more BTUs than you demand based on the square footage alone.^[10]

6. six

   Gene in the unit's efficiency rating. While furnaces are rated past their effectiveness in delivering the heat they generate, air conditioners are rated past how efficiently they utilize electricity over the class of a typical operating twelvemonth. I such rating is the Seasonal Energy Efficiency Ratio (SEER) rating, created past the Air Conditioning, Heating, and Refrigeration Establish, which is the ratio of the unit's cooling output in BTUs divided past the free energy in watt-hours needed to run information technology for the unabridged operating twelvemonth. (Note that 1 kilowatt-hr equals ane,000 watt hours.)^[11]

   • For instance, have a iv,000 BTU/hour air conditioner run for one,000 hours during an operating twelvemonth using 400,000 watt-hours of electrical ability. This air conditioner would take a SEER rating of 10, since iv,000 ten i,000 / 400,000 = 10.
   • To find the average ability consumption, carve up the unit's power in BTUs per hour by the SEER rating. Since the SEER rating is in units of BTU per Watt-hour, your reply will be in terms of watts. In the example above, (4,000 BTU/h) / (10 BTU/Wh) = 400 W.
   • Central air conditioners manufactured in the United states of america since January 2006 are required to have a SEER rating of at least 13, or xiv to be Energy Star qualified. Room air conditioners are currently exempt from this requirement; many have SEER ratings closer to x.

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BTU Cooling Capacity Chart

Add New Question

• Question

  32,000 BTU equals what in tons?

  

  The math indicates 2.6; all the same, a 2.6 is not manufactured, so you're dealing with a 2.5 T unit. Take the rated BTUs, 32 K/12,000. 12,000 represents BTUs per ton.

• Question

  What size air conditioner should I buy for a 1,446 square pes home that has a vaulted ceiling in the living room?

  

  30,000-36,000 BTU, depending on how many foursquare anxiety the living room takes upwardly, how much higher than a normal 8' ceiling the vault is, how much glass yous have, and how well insulated the home is.

• Question

  How many BTUs do I need for a 906 square pes house?

  

  Anywhere from 17,500 - xviii,500 BTUs. Information technology depends on how well insulated the domicile is and how much glass you have.

• Question

  If I'chiliad buying a house that is 2145 sq. ft., will a 2 ton heat pump heat and absurd it adequately?

  

  Definitely not. Depending on how well the house is insulated, I'd say you lot need anywhere between 3.5 and 4 tons.

• Question

  Do I include the basement expanse in the full heating area in calculations to size the furnace?

  

  Yes, if you intend to heat the basement.

• Question

  63,000 btu with seer of 14 -- what tonnage a/c would you advise in an older home?

  

  Information technology depends on your prevailing climate. For an boilerplate US climate, a two-ton A/C unit would be sufficient.

• Question

  How do I summate how much baseboard heater capacity I tin connect to a xv AMP billow?

  

  Per the National Electrical Code (NEC), in general, the calculated load cannot exceed lxxx% of the circuit rating. Therefore, 80% of 15 AMP = 12 AMP max load. Assuming U.S. nominal voltage of 120V, the maximum heater rating is 120 Volts x 12 Amps max which ways 1440 Volt-amps max bold it is a standard resistance heater. If the circuit billow (CB) is a 15 Amp 2-pole CB and the nominal voltage between the two poles is 240V; the maximum heater rating would be eighty% x 15A x 240V = 2880 Volt-Amps max or 2880 Watts max for a standard resistance heater.

• Question

  Will the height of the room affect the calculation?

  

  It will not usually, just every bit a basement does not bear on the furnace requirements. Nevertheless, if the ceilings are over 12 feet, you might want to double upwards the square footage for that infinite.

• Question

  Volition an air conditioner with a cooling capacity of 27,600 cool a 22,500 square foot home during hot summers?

  

  You will need several Air-conditioning units. 22,500 square feet. is about the size of well-nigh ten large houses.

• Question

  The gas guy ordered my new Intertherm furnace for my mobile home. I told him the square footage is 1150, but didn't tell him that 200 of that is an add together-on with no vents from the furnace. Is this dangerous?

  

  No, information technology should be fine.

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• There are many online BTU calculators you tin can utilize.

• If y'all're mounting a room air conditioner in a corner window, wait for i that can ship airflow throughout the room, non into the wall.

• Central air workout units frequently have the capacity coded into the model number; for example, model RDR36 would be a 36,000 BTU unit of measurement. They may also report their size every bit tonnage, with 12,000 BTUs equal to 1 ton (the amount of power needed to melt i ton of ice in 24 hours); thus the model RDR36 would be a 3-ton unit.

• A poorly insulated habitation volition lose a lot of estrus to drafts. Insulating may let you to apply a furnace with a smaller BTU rating.

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• Don't purchase a room or central air conditioner with a greater chapters than you need. If you lot do, the unit volition cool the room too rapidly to also have the humidity out of the air. An oversized key air conditioner will besides turn on and off more than frequently, which costs more and wears out the unit of measurement more quickly.

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Article Summary X

To calculate BTU per square pes, showtime by measuring the square footage of each room you want to rut or absurd. Then, add the square footage for each room together. Once you have the total square footage, just multiply that number by 20 to find how many BTUs per 60 minutes yous'd need to heat or cool the space. For example, if you're trying to heat or cool 1,000 square feet, you lot would multiply 1,000 by 20 and become 20,000 BTUs per hour. To acquire how to adjust BTU per foursquare human foot for special weather, scroll down!

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