5 Facts you may not know about Air Conditioning

5 facts that you may not know about your Air Con:

The vast majority of homes, offices and hotels in hot humid climates have air conditioning. Air conditioning may be a luxury for some, but for all estate managers, hotel and office owners and many consumers, it is a necessity.

Bearing in mind the expense of the equipment and the power required to maintain effectively for longevity, health and comfort, it would be beneficial for consumers and users to be better informed about their air conditioning systems.

The following guidance will make an energy consumer more aware of an air conditioning system and more knowledgeable about how to care for and use it well. If it becomes necessary to replace a system, however, do not hesitate to seek out a qualified HVAC professional for expert advice and assistance.

What we will be asking:

1. What is Air Conditioning?
2. What is a ton of cooling?
3. What goes wrong?
4. What filters do
5. Maintaining the system

What is Air Conditioning?

The first known Air Conditioner (AC) was patented in 1907 – credit goes to a Willis Carrier, who is reputed to have been a brilliant engineer. His company grew quickly servicing office buildings in the 1920s with cool air.

Despite the development of the centrifugal refrigeration machine and the commercial growth of air conditioning, the company ran into financial difficulties during the Wall Street Crash in October 1929. In 1930, Carrier Engineering Corporation merged with Brunswick-Kroeschell Company and York Heating & Ventilating Corporation to form the Carrier Corporation, with Willis Carrier named Chairman of the Board.

Their definition of Air Conditioning still stands today:

To; Maintain suitable humidity in all parts of a building
Free the air from excessive humidity during certain seasons
Supply a constant and adequate supply of ventilation
Efficiently remove from the air micro-organisms, dust, soot, and other foreign bodies
Efficiently cool room air during certain seasons
Heat or help heat the rooms in winter
An apparatus that is not cost-prohibitive to purchase or maintain

Here comes the technical question:

How and Air Conditioner works

The purpose of your home air conditioner is to move heat from inside of any building to the outside, thereby cooling you and the ‘inside environment’.
Air conditioners blow cool air into your home by pulling the heat out of that air. The air is cooled by blowing it over a set of cold pipes called an “evaporator coil”. This works much like what happens when water evaporates from your skin.

The evaporator coil is filled with a special liquid called a refrigerant, which changes from a liquid to a gas as it absorbs heat from the air. The refrigerant is pumped outside to another coil where it gives up its heat and changes back into a liquid.

This outside coil is called the condenser. The gas is condensing back to a fluid just like moisture on a cold window. A pump, called a compressor, is used to move the refrigerant between the two coils and to change the pressure of the refrigerant so that the entire refrigerant evaporates or condenses in the appropriate coils.

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The energy to do all of this is used by the motor that runs the compressor. The entire system will normally give about three times the cooling energy that the compressor uses. This odd fact happens because the changing of refrigerant from a liquid to a gas and back again lets the system move much more energy than the compressor uses.

What is a ton of Cooling?

Before refrigeration air conditioning was in use, cooling was achieved by using big blocks of ice. Therefore when cooling machines started to be used, they rated their capacity by the equivalent amount of ice melted in a day, which is where the term “ton” came from when sizing air conditioning systems and their effect.

BTU stands for British Thermal Units and has become a standard for measuring air conditioner capacity.

A BTU is a number derived from multiplying the area of the room to be air conditioned in square feet by 30. So for example if your room measures 15 feet by 12 feet, you would need an air conditioner with about 5400 BTUs (15 x 12 x 30) to cool the room.

However, 5400 may not be enough when you factor in other variable factors such as: how well your rooms will cool, presence of direct sunlight, high ceilings, and leaks under doors or in cracks.

These thermal units are used by engineers to assess the size of the unit needed to cool the size of room – a window air conditioner is usually less than one (1) ton. A small home central air conditioner would be about two (2) tons and a large one about five (5) tons.

What goes wrong?

Air conditioners are complex mechanical systems that rely on a wide variety of conditions in order to work correctly. They come in different sizes to meet a certain “load” of the area they are meant to cool.

They are designed to have certain amount of refrigerant, which is known as the “charge”. The are designed to have a certain amount of air flow across the coils. When any of the conditions that apply when fitted do change, the system can start to have problems.

If you are creating more heat than usual inside, such as from having guests or extra appliances or because of other changes in the house, the air conditioning may not be able to keep up.

If the refrigerant charge on the system leaks out, it lowers the capacity of the system. You will simply get less cooling and the system will not be able to keep up when the load gets high.

If airflow across the outdoor (condenser) coil is reduced, the ability to push out heat to the exterior is reduced and the again the capacity of the system may go down, especially at higher outdoor temperatures.

In dry climates, the same issues happen with regard to the indoor (evaporator) coil – higher airflow helps, lower airflow impairs the system. In humid climates, the situation is more complex.

At higher airflows, there will be less dehumidification, leading to high indoor humidity. If the airflow gets too low, however, the evaporator coil may freeze.

This worsens performance and can damage the compressor until it fails – causing an expensive repair bill and getting hot under the collar literally!

What Filters do

Almost every air conditioning system has a filter upstream of the evaporator coil. This can be in the return grille or in special slots in the duct system and is the gauze-looking device almost anyone can take out and clean now and again. Its main job is to stop big particles from entering the system.

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As the filter does its job, it gets loaded with more and more particles. This actually has the effect of making the air cooler, but it also increases resistance and reduces airflow. When this happens, it’s time to change the filter. How long it takes to happen depends on how dirty the air is and how big the filter is.

If you are slow to change the filter, the air flow will reduce and the system will not perform well. Not only that, but if the filter is very dirty, it starts to send nasty air back into your environment contributing to colds and fevers.
You may find for a while that the AC unit works better without ?????.

Whilst this may be true, the dust and particles building up on the coils will mean ultimately shorten the useful life of your AC unit.

Dirty filters

When you do buy a new filter, we recommend getting one with a Minimum Efficiency Rating Value of MERV 6 or higher.

Maintaining the system.

Routine maintenance such as changing filters can be handled by most in-house staff and consumers in domestic homes, but other maintenance tasks typically require professional service.

If the system is not producing as much cold air as under normal operation, it may also be an indication of refrigerant charge or airflow problems. These problems may also require servicing.

Many AC units in environments being used by many people all sharing the same air need to have a professional team to monitor its operational condition, relative to Indoor Air Quality standards in warmer climates like in South East Asia, where people spend 90% of their time under air conditioning – a primary concern for estate managers, and office and hotel owners.

AESS has over 50 years of cumulative experience of AC Maintenance Services in the UK and the Head office is now in Bangkok and local regions – helping building owners ensure they provide a healthy environment for their residents and saving building owners considerable money and out-of pocket expenses implementing advanced energy savings solutions

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