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AIR CONDITIONING & HEAT PUMP SYSTEMS

AGE of AIR CONDITIONERS & HEAT PUMPS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR FILTER EFFICIENCY
AIR FILTERS, FIBERGLASS PARTICLES
AIR FLOW MEASUREMENT CFM

BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books

CAPACITORS for HARD STARTING MOTORS
CAPILLARY TUBES
CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
CLEANING & Legionella BACTERIA
CONDENSING COIL
COOLING LOAD REDUCTION by ROOF VENTS
CRITICAL DEFECTS on A/C SYSTEMS

DEFINITION of Heating & Cooling Terms
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM NOISES
DUST, HVAC CONTAMINATION STUDY

ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATOR COIL or COOLING COIL
EVAPORATIVE COOLING SYSTEMS

FAN NOISES

GAUGE, REFRIGERATION PRESSURE TEST

HEAT LOSS (or GAIN) in buildings

INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS

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 & DIAGNOSTIC FAQs for A/C
RETROFIT SIZING for A/C or HEAT PUMPS

SYSTEM OPERATION

WATER COOLED AIR CONDITIONERS

More Information

How to Choose a Room Air Conditioner - BTU Chart       BTU CHART for AIR CONDITIONERS / HEAT PUMPS - How to choose an air conditioner that fits the building and your cooling needs? Typical BTU Cooling Capacity Range for Types of Room Air Conditioners Room Air Conditioner or Window Air Conditioner Sizing and Choosing Chart How Much Cooling Capacity do we need Per Square Foot of Building Area? How Much Space can a Ton of Cooling Capacity Serve? How To Calculate the BTUs needed to cool a given space: follow this procedure: How big an air conditioner do I need? How much air conditioning do I need? How many BTUs or Tons of Air conditioning? Can an air conditioner be too powerful for the building? Watch out: Don't Buy an Oversized or "Too Big" Air Conditioner Questions & Answers about how to determine the necessary cooling capacity in BTUs for a room or building area cooled by a window air conditioner or a portable air conditioning unit References

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Air conditioner BTU requirements: this article provides an air conditioner BTU chart shows how to choose a room air conditioner for window or through-wall mounting. We also show how to calculate how much BTU capacity you need based on building area or square feet, and we warn about dehumidification problems if you buy an air conditioner that is too big for the space you are cooling. Also see WINDOW / WALL AIR CONDITIONERS.

Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.

Typical BTU Cooling Capacity Range for Types of Room Air Conditioners

Also see   COOLING RULES OF THUMB to guesstimate how many tons or BTUs of cooling a building needs and see RATED COOLING CAPACITY to determine the cooling capacity of existing air conditioning equipment. We discuss the air conditioning system sizing problem at AIR CONDITIONER BTU CHART and while details are found at DEHUMIDIFICATION PROBLEMS, we also introduce the oversized air conditioner problem at LOST COOLING CAPACITY. At ADDING A/C: RETROFIT SIZING we discuss home cooling system sizing mis-match on retrofit jobs. Portable, window, or through-wall air conditioners are typically described by their manufacturer as suited for: Single Room Air Conditioner Capacity - typically for rooms up to 20' x 20' or 400 sq.ft. in area. BTUs in this product range are typically from 6,000 BTUh to 10,000 BTUh. Portable room air conditioners - 7,500 to 14,000 BTUH, portable, using one or in some cases two flexible ducts to move heat from the room, through cooling coil and the compressor, to outdoors Multiple Room Air Conditioner Capacity - typically for a total area of up to 800 sq.ft. BTUs in this product range are typically from 10,000 BTUh to 16,000 BTUh. Large Capacity Air Conditioner Capacity - typically for multiple rooms or very large rooms up to a total area from 900 sq. ft. to 2,000 sq.ft. BTUs in this product range are typically from 16,000 to 28,000 BTUh. Central Air Conditioning - typically to cool an entire floor or multiple floors in a home. Also see A/C TYPES, ENERGY SOURCES

Room Air Conditioner Sizing and Choosing Chart

The table below gives recommended air conditioning BTU's necessary to cool a single room. The data in the table assumes that the ceiling over the room is insulated and that the room is not over or is not itself a special heat-producing area such as a kitchen or boiler room.

Table 1: Base BTUs - Recommended Air Conditioner BTUs
Number of Rooms Cooled	Room Area MINimum sq.ft.	Room Area MAXimum sq.ft.	BTUs Needed
One	.	100	4,000 - 6,000
One	100	180	6,000 - 7,500
One	180	270	7,500 - 9,000
One	270	400	9,000 - 10,500
Several	.	400	10,500 - 12,000
Several	400	500	12,000 - 13,500
Several	500	700	13,500 - 15,000
Several	700	800	15,000 - 16,500
Large Areas	.	900	16,500 - 18,000
Large Areas	900	1000	18,000 - 19,500
Large Areas	1,000	1,100	19,500 - 21,000
Large Areas	1,000	1,100	19,500 - 21,000
Large Areas	1,100	1,200	12,000 - 22,500
Large Areas	1,200	1,500	22,500 - 24,000
Large Areas	1,500	1,700	24,000 - 25,500
Large Areas	1,700	1,900	25,500 - 27,000
Large Areas	1,900	2,200	27,000 - 28,500

How To Calculate the BTUs needed to cool a given space: follow this procedure:

1. Calculate the total square feet to be cooled: Measure the size of the room (or rooms) to be cooled, to obtain total square feet. Multiply room length by width for each room and if there are multiple rooms, add the room areas together to get a single number.
2. Read the Base BTUs needed from Table 1 below
3. Add additional BTUs for these factors:
• + 4,000 BTUs for each room below a ceiling or roof which is not insulated
• + 4,000 BTUs for a home or residential kitchen included in the cooled area
• + 1,500 BTUs for each window which receives significant daily sunshine
• + 1,500 BTUs for a room over a kitchen or boiler room IF the kitchen or boiler room is actively producing heat during the cooling period
• + 600 BTUs per person over two, if more than two occupants will be occupying the room during the cooling period
4. Subtract BTUs from the total required if these factors are present:
• - 1,000 BTUs if the room is on the shaded side of the building
5. Calculate the final total BTUh needed from the above steps. This should place you in the right range of cooling capacity needed. Review the warning below about buying an oversized air conditioner.

How Much Cooling Capacity do we need Per Square Foot of Building Area? How Much Space can a Ton of Cooling Capacity Serve?

Maybe 450 sq.ft. to 1000 sq.ft. of a typical home can be cooled per ton of cooling capacity: that is, one ton (or 12,000 btuh) of air conditioning can cool about 500 sq.ft. of space. Sketch courtesy of Carson Dunlop Associates.

But the real answer is, it depends. Some of the factors that affect the ability of an air conditioner to cool a space need to be considered besides just the number of square feet. These include at least the following questions about air conditioning load and cooling requirements:

• What are the sun and heat characteristics of the geographic area where the building is located (southern U.S. vs. northern U.S. or Canada, for example)?
• How much direct sunlight is falling on the building?
• Is it bright hot sun or only partly sunny?
• What are the exterior colors of surfaces on which sunlight is falling?
• How well the building is insulated?
• How drafty is the building?
• How many occupants are in the building?
• What other heat sources (or cooling sources) are in the building?
• How high are the interior ceilings?
• How does air circulate within the occupied spaces?
• What defects in the air conditioning system need to be overcome, such as duct system errors or damage, dirty filters, blocked cooling coils, etc. ?

Watch out: Don't Buy an Oversized or "Too Big" Air Conditioner

Watch out: Do not buy an air conditioner which is oversized (too many BTUh) for the area you need to cool. You may think that bigger is better, but not in the case of air conditioning. To make a room comfortable the air conditioner needs to both cool the room air AND dehumidify the room air. If the air conditioner is too large for the space to be cooled, the temperature will drop quickly and the A/C unit will shut off before the air has become adequately dry. The room will be either too cold or too humid for comfort. Sketch courtesy of Carson Dunlop Associates. More detail about how to diagnose and cure an air conditioner that is not dehumidifying can be found at DEHUMIDIFICATION PROBLEMS

Other types of portable or individual-area air conditioners

• Heating & Cooling units - capable of both cooling or heating a room using electricity. Basically these units are small heat pumps that are mounted in a building window or wall. Heating/Cooling units will give two different BTUh figures, one for cooling and one for heating.
  
  These figures will differ, for example, producing 18,000 BTUh in cooling mode but only 12,000 BTUh in heating mode. The difference between heating and cooling, and the amount of heat actually available will depend also on the outdoor temperatures when in heating mode (as with any heat pump system, the unit cannot provide heat below certain temperatures.)"
  
  
• Slider or Casement Window units - narrow tall cooling systems which are designed to fit into the narrow space provided by casement or slider windows.
  
  
• Through-wall air conditioners - air conditioning units which are designed to be installed into a metal sleeve which is then itself installed in an opening cut into the building wall, leaving windows unobstructed, or perhaps for use in a room without a suitable window in which an air conditioner could be placed. BTU output is typically a bit more than the smallest window air conditioners but otherwise is similar in range.
  
  
• Portable air conditioners - units on wheels which are plugged into an outlet but can be moved room-to-room and do not require a window for their exhaust. These cooling units are of modest cooling ability, typically around 10,000 BTUh though some producers such as Sunpentown offer units up to 14,000 BTUh. See PORTABLE ROOM AIR CONDITIONERS for details about portable room air conditioners.

How to Determine BTUs or Tons of Cooling Capacity of an Air Conditioner from its Data Tags

See RATED COOLING CAPACITY for an explanation of how to determine the cooling capacity of an air conditioner that is already installed at a building or go directly to these links within that article:

  FROM MODEL # - how to determine the BTU capacity or Tons of cooling capacity of an air conditioner from model number
  FROM EQUIPMENT RLA # - how to determine the BTU capacity or Tons of cooling capacity of an air conditioner from the RLA number
  COOLING RULES OF THUMB - how to guesstimate how many tons or BTUs of cooling a building needs

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