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Air Conditioning Units
- Air Conditioning Equipment (How their strength is displayed)
- Air Conditioning Unit Types (by strength)
- Air Conditioning Unit Types (by types)
Establishing the Cooling Capacity of Air Conditioning Equipment
Cooling capacity of an Air Conditioning System is stated in MBTUH’s (BTU’s) or tons
1 TON = 12 MBTUH (12,000 BTU’s) per Hour of cooling capacity
How much cooling power per hour (Historically, the amount of cooling needed to melt 1 Ton of Ice!)
Whilst Serial Number formats vary by ‘Maker/Country/Age of unit’,
sometimes it’s cooling capacity is included. Newer units show this information.
RLA : Rated Load Amps may suggest cooling ability.
5 to 6, (7 in some cases) RLA = 1 ton of cooling capacity
21.2 for example, divided by 7=3 Tons.
In reasnably cool summer climates such as the UK/Northeastern United States:
1 ton per 400 sq .ft. (Commercial) or one
ton per 700 to 1000 sq .ft. (Residential)
In ‘Hot Climates’, that can be halved.
3000 sq .ft. house may require a 5-ton unit. Or count the supply outlets: 10 outlets @ 100 cfm (estimated) = 1,000 cfm = 2.5 tons needed.
Cooling an areas is not the only route to comfort. If too powerful, over cooling reduces the effectiveness of removing moisture from air. Making the enviroment too humid. (An Air Conditioning System not being on for long, indicates this and reduces the Air Conditioning Units lifespan.
Typical square feet (Sq Ft) of properties (houses & Flats) in the UK
10 by 12 Room is 120 sqft
Edwardian Lounge with dining area 300 sq ft
Studio 300 to 600 sq ft
1 bed Flat 500 to 1000 sq ft
2 bed Flat 800 to 1,500 sq ft
2 bed House 1,200 to 2,000 sq ft
3 Bed House 2000-3000 sq ft
4 – 5 Bed House 3000-5000 sq ft
(divide by a little less than 10, remove a zero, for approximate m² )
Which AirCon will do the job?
Calculating the BTUh needed:
- Calculate the total square feet to be cooled (sqfeet)
(Multiply length by width for each room and add totals together)
- See where it fits on the Table below
Table 1: Base BTUs – Recommended Air Conditioner BTUs No. of
Rooms to be Cooled
sq.ft. of room sq.ft. of room Recommended
FROM TO One Zero to 100 4,000 – 6,000 One 100 to 180 6,000 – 7,500 One 180 to 270 7,500 – 9,000 One 270 to 400 9,000 – 10,500 Several Zero to 400 10,500 – 12,000 Several 400 to 500 12,000 – 13,500 Several 500 to 700 13,500 – 15,000 Several 700 to 800 15,000 – 16,500 Large Areas Zero to 900 16,500 – 18,000 Large Areas 900 to 1000 18,000 – 19,500 Large Areas 1,000 to 1,100 19,500 – 21,000 Large Areas 1,000 to 1,100 19,500 – 21,000 Large Areas 1,100 to 1,200 12,000 – 22,500 Large Areas 1,200 to 1,500 22,500 – 24,000 Large Areas 1,500 to 1,700 24,000 – 25,500 Large Areas 1,700 to 1,900 25,500 – 27,000 Large Areas 1,900 to 2,200 27,000 – 28,500
- Adjust for any warming or cooling factors
Warming Effects + 4,000 for each room below a unisulated ceiling/roof + 4,000 for each kitchen that is to bwe cooled + 1,500 for each sunny window + 1,500 for a room over a kitchen or boiler room if being used + 600 per person within the area, if over two Cooling Effects - 1,000 BTUs if the room is on the shaded side of the building
Air Conditioning Unit Types
Choosing the right Air Conditioning Unit for the space: Portable or Mounted (in Window or Within Wall)
- Recomended ‘Single Room’ Air Conditioning Unit
For rooms of 20′ x 20′ max (400 sq.ft.)
BTU : from 6,000 BTUh to 10,000 BTUh.
- Portable room air conditioners
For a room (around 20′ x 20′)
7,500 to 14,000 BTUH (ducts remove heat from the room to outside)
- Multiple Room Air Conditioner Capacity
Building of 800 sq.ft.
10,000 to 16,000 BTUh.
- Large Capacity Air Conditioner Capacity - typically for multiple rooms or Building or large rooms of 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
floor or multiple floors in a home
20,000 BTUh +
Air Conditioning Unit Types
Getting the right Air Conditioning System for the property
- Combined Units : Heating & Cooling -
Often wall or window mounted, these are handy for compact properties, where there is little space
- Slider or Casement Window units -
Tall, narrow, cooling units which are good where floor and wall space is limited, as they fit
the narrow area provided by casement window.
- Wall mounted air conditioners -
Good for properties with an outside wall, especially with period, attractive, windows.
A metal enclosure is installed in the opening, cut into the building. Output (BTU) is typically higher than smaller window air conditioning units.
- Portable air conditioners -
Movable, wheeled, units that offer modest cooling strength and are plugged into a standard power point (outlet). 10,000 BTUh to 14,000 BTUh, as a typical maximum. Equating to 400sq feet in one room or possible several that are connected. Good for windowless rooms, as they do not require an outlet for their exhaust. They can also prevent
Single Hose Portable Room A/C Unit
Air from the room/property is:
Sent out as cold air AND for the exhaust from the unit (used to cool compressor).
Positives: Better energy efficiency and keeps air usage within confinds of room
Negatives: It creates a negative air pressure, pulling in air from other rooms/areas and cooles area slower.
- Dual Hose Portable Room A/C UnitAir from the room/property is:
Sent out as cold air BUT draws in outside air for the exhaust from the unit (used to cool compressor).
Positives: No negative pressure created within the room, meaning rooms cools quicker. 90°F or higher, outside, or when humidity is high 80%, second hose should not be used (to avoid overheating)
Negatives: Consumes more energy (has two internal fans)