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      Length (m) Width (m) Height (m)



BTU      to British thermal unit
Watts      to .


Please note!

The BTU calculator is only a guide

the calculation will vary depending on location, no of occupants no of electrical devices & the amount of glazing
     as well as floor finishes & a heat load calculation should be done by a qualified person





                               Hot and Cold :: Air conditioning ::  Under floor heating !!

What is air conditioning?

Air conditioning is the ability to simultaneously and effectively control the temperature, humidity, air movement and the quality of the air in a given space.

How does an air conditioner work?

Heat naturally flows from a warm to a cold substance, so air can therefore be moved from over a warm is a cold surface desired effect. This warm or cold surface can be obtained only through a process called ‘The Refrigeration Cycle’. This refrigeration process provides cooling below ambient temperature by transferring heat from one area (where it is not wanted) to another area (where it is not objectionable).

What types of air conditioners are available?
  • Window / Wall Type: This system is designed to fit through a hole in the wall or in a window frame. It is also known as a ‘self-contained’ air conditioner as the ‘indoor’ (evaporator) and ‘outdoor’ (condenser) parts are encased in a single housing. It is necessary to install this all-in-one air conditioner on an external wall/ window in order for the heat to be disposed of via the back of the unit (condenser section.)
  • Split type: This type comprises an indoor unit (Fan Coil Unit / Evaporator) and an outdoor unit (Condenser Unit). There are a number of indoor split type air conditioners i.e.
    • Wall Mounted (mid wall split)
    • Ceiling Mounted (cassette split)
    • Ducted Type
What does an air-conditioner consist of?

A typical air conditioning unit has four main components for the cooling cycle:

  • Evaporator
  • Compressor
  • Condenser
  • Capillary Tube
What are heat loads?

Remember, all the air in a given space needs to pass through the refrigeration cycle (air conditioner) for there to be ‘effective control’ of that area. Therefore, air conditioning can only be effective if the area to be cooled or heated is a sealed environment. For additional heat loads to BTU, the following calculation/s could be used:

  • People - Add 400-600 BTU / person (average) depending on activity
  • Electrical Equipment – Wattage x 3.4 = BTU (e.g. a 100W light = 100 x 3.4 = 340 BTU)
How do you calculate the heat load?

Here follows a guide only. For a precise heat load calculation, a Heat Load Calculation Sheet should be completed. For offices, homes and your average area requiring air conditioning always keeps the following factors in mind:

  • Size of the area (m²): If the height of the ceiling is over 3m, then add on the increased percentage of the area, or use the Heat Load Calculation Sheet
  • Exposure to direct sunlight: Is there excessive heat gain from large or many windows or a non-insulated roof etc?
  • Curtains and blinds: If the area is an office with blinds or glazed windows, the heat gain is reduced.
  • Type of building construction: A brick construction will generally be cooler than a timber or metal one.
  • Number if people in the area and level of activity: An office with two people can be considered a ‘standard’ heat load. However, an office of the same size with eight people is not. A person seated at an office desk gives off less heat than someone who is more active e.g. in a reception area or a restaurant eating and drinking.
  • Extraction and intake of air: If the air is added to an area (e.g. via an open window), this air will be warmer than the air in the given area and will need to pass through the refrigeration cycle to lower its temperature, causing the air conditioner to work ‘harder’. Thus the capacity is affected.
  • Electrical equipment in use: An empty office in a building with no people in it might not generate much of a heat but in a computer room, the heat generated by the equipment will increase the heat load, affecting the capacity. An excessive number of lights will have a similar effect. Should the area being calculated be considered a ‘standard’ heat load, then the following average heat load calculation could be used: 500 BTU / m²

Window / Wall unit – Self-Contained
A basic entry level air conditioner. This all-in-one unit is ideal for ‘smaller’ spaces such as offices or homes with an area not exceeding 48m². Simple and cost effective to install.

Split Type Unit – Mid wall
This air-conditioner is purpose designed for most offices or homes with an area not exceeding 60m² and has more features than the Window / Wall unit. (Quieter but more costly)

Split Type Unit – Ducted
This air-conditioner has one indoor unit mounted in the ceiling, cooling one or more areas via ducts to a grille exposed on the ceiling or wall. A cost effective method for many areas.

Split Type Unit – Cassette
This air-conditioner has one indoor unit mounted in the ceiling with an exposed grille on the ceiling. An ideal solution for shops or large open plan areas.

How should I maintain my conditioner?

Air conditioners are technically complex products that require regular maintenance. Failure to heed these requirements could result in reduction of product life span as well as breakdowns of expensive parts.

Recommendations on maintenance include:

  • When choosing a position for an air-conditioner, bear in mind the need for easy access in order to carry out maintenance work.
  • If an unusual decrease in cooling/heating capacity occurs, turn off the air conditioner and contact your nearest authorised dealer: this will avoid expensive repairs.
  • Air-conditioners are designed to function when outside temperatures are above zero. Serious damage can occur to the unit if operated at outside temperatures that are below zero.
  • Ensure cleanliness of indoor and outdoor units.
  • Contact an authorised dealer at least every six months to carry out as required maintenance.
  • The installation and/or maintenance work should be performed by an authorised dealer and/or installer. If the installation and/or maintenance work is performed by unauthorised dealers or installers, the manufacturer will not be held liable for any damage or incorrect installation.

The owner is liable for any cost incurred for the installation and maintenance of the air conditioner, as the product warranty does not cover any of these costs.

What size aircon do you need?

For a precise assessment of the correct size of airconditioner required, a qualified aircon installer will need to do an on-site check as there are a number of different factors to consider. The following information will however give you an approximate guide to the aircon capacity required for a particular area.
Please use the table below to help calculate the size of your room by multiplying the length of your room by the width.

For a room of approximately: Aircon Size Required:
15 to 18 m²: 9 000 BTU
20 to 25 m²: 12 000 BTU
30 to 35 m²: 18 000 BTU
40 to 45 m²: 24 000 BTU
55 to 60 m²: 30 000 BTU

The difference between an inverter and non inverter:

The difference between an inverter and non inverter is the inverter units can alter their speed in response to cooling demand. Some units have an initial over-speed period where they will run at a slightly higher capacity for a set time to pull down the temperature of a hot room. When they reach the set point temperature they can reduce capacity to maintain that level without cycling as much as a normal unit would. This saves power although it’s arbitrary as it would still take a while to recoup the increased purchase costs.

The inverter unit increases the power usage slightly as it converts the incoming power into a suitable style for the air conditioner although the ability to run at a reduced power level helps to drop the overall usage to below that of a typical non-inverter unit. Most of the advertising claiming 30% lower bills using inverters are based on very carefully set up laboratory scenarios. In reality, while they may cost less to run than a conventional unit, buying an efficient conventional unit will still be cost effective.


This information is brought to you with the compliments of Samsung.

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