Frequently asked questions

This may occur during the defrosting procedure, when the air-conditioner is in heating mode. This perfectly normal phase is part of the protection system. During the defrosting process, the appliance will thaw the accumulated frost on the outdoor unit, and when the ice melts, some of the water droplets may turn into steam. This process should last no more than 10-12 minutes.

It can recur from time to time.

The appliance is probably in air-conditioning mode when the outside temperature is low.

This may occur from time to time as the unit cools the air and may therefore sometimes mist up. Check that the filters on the indoor unit are clean; this may reduce the phenomenon.

Pollen and allergens are impurities in the air that can trigger allergic reactions in some people.

In an urban environment, when these allergens mix with other impurities present in the air and known as adjudicants, such as Diesel Particle Matter (DPM) produced by engines and Volatile Organic Compounds (VOCs) present in building materials and cosmetics and elsewhere, can transform the allergens into heavy allergens, which may then exacerbate the adverse health effects of these allergens and cause aggravated symptoms and trigger latent allergies.

With a well-maintained air-conditioning system and regularly changed filters, the air-conditioning will even be your best ally against hay fever, rhinitis or various other allergies.

There may be two reasons:

1. The first is related to the minimum compressor “off” time; in other words, the appliance was switched on and off and then switched on again. The minimum ignition time is three minutes, to avoid damage to the compressor.
2. The second is that if the unit is in heating mode, the indoor fan will not turn on until the indoor coil is warm enough to prevent cold draughts.

The appliance is probably in air-conditioning mode when the outside temperature is low.

This may occur from time to time as the unit cools the air and may therefore sometimes mist up. Check that the filters on the indoor unit are clean; this may reduce the phenomenon.

1. In the first stage, the compressor diffuses the coolant in gaseous state into the condensing coil, and the coolant, being on the high pressure outlet side of the compressor, will be heated and drawn into the condensing coil.
2. As the coolant passes through the condensing coil, the high-pressure gas will release heat because the air is forced through the condensing coil by the outside fan, and the coolant will be sub-cooled and converted to a high-pressure refrigerant fluid.
3. At this point, the sub-cooled refrigerant fluid passes through a diffusion device via a small hole, which will immediately reduce the pressure. As a result, the refrigerant fluid will also drop in temperature.
4. The low-pressure refrigerant fluid will circulate through the evaporator coil and absorb heat from the room, because of the indoor fan blowing air into the evaporator coil. As the coolant absorbs heat, air passing through the inner coil will cool and the refrigerant fluid will boil and change from a low pressure liquid to a low pressure gas until it returns to the compressor.

For the heat-pump function, the cycle is reversed, meaning that the compressor will discharge into the indoor coil rather than the outdoor coil, as is the case in cooling mode.

This component is known as a four-way valve (heat pump) that operates the change of direction.

Only poorly maintained air conditioning risks making you ill. A well-maintained air-conditioning system, on the other hand, contributes to a healthy atmosphere.

Moisture

By controlling humidity levels, air conditioning reduces the growth of mould and dust mites. Air conditioning keeps the humidity level between 40% and 60%, which is quite beneficial for allergy sufferers.

Ventilation

Some air conditioners have built-in ventilation systems. The presence of mechanical ventilation systems is now becoming essential because of current construction methods. The provision of fresh air prevents the onset of sick building syndrome.

Filtration

It is essential to replace filters at a specific time. If the filters are replaced too late, they may become saturated and spread bacteria instead of capturing them. All air conditioners are equipped with a filter. The filtration method varies according to the type of installation and the client’s needs. The effectiveness of a filter can extend from filtration of dust and particles to filtration of fine dust, pollen, bacteria, viruses, odours, microbes and smoke particles.

Air currents

If the equipment is chosen correctly, there will be no risk of draughts. However, this is a specialist job and as such must carried out by the installer. An air conditioning system with insufficient capacity will not reach the desired temperature. Installing a system with excessive capacity will cause draughts and temperature fluctuations,

Over time, we have sought to improve the level of comfort offered by our environment. We have tried to warm our homes in colder regions and cool them in warmer regions, because too low or high a temperature prevents us from working properly or relaxing. However, the thermal comfort essential to our well-being is subject to three factors:

• The human factor
  the way we are dressed, our level of activity, and the time we spend in one position
• Our space
  the radiation temperature and the surrounding temperature
• The air
  its temperature, speed of movement and level of humidity

Of all these factors, the human factor remains the most unpredictable. However, the others can be controlled to provide that much-needed sense of well-being. Changes in building patterns, working patterns and occupancy rates have created new parameters that designers must take into account.

For example, modern buildings generate much more heat than buildings dating from 50 years ago, say, for several reasons:

• Solar infiltration
  Advances in building technology have led to increased use of glass, and even with solar control glazing, the impact of the sun’s rays remains considerable.
• Occupants
  An increasing number of occupants, each generating as much as 120W/h of heat, are regularly crammed into office buildings.
• Electrical appliances
  Computers, printers and photocopiers, now essential in every office, also generate a significant amount of heat.
• Lighting
  Many modern shops could be heated by their lighting systems alone, which often give off between 15 and 25 W/m².
• Ventilation
  Introducing outside air into a building also means introducing its temperature, which can be problematic when it is 30°C outside!

Heat always flows from a warmer substance to a colder substance. It is actually a transfer of energy between fast-moving and slower-moving molecules. This means that faster molecules slow down a little and slower ones speed up. To put it more simply, this means that when it is warm outside, heat tries to “invade” the cooler interior spaces.

Heat can be transferred from one body to another by one of three processes:

• Radiation
  By a moving wave (identical to light waves) which transmits energy from one body to another without the need for intervention.
• Conduction
  By a flow of heat between parts of a substance or from one substance to another by direct contact
• Convection
  By transfer via a fluid or via the air.

Cold draughts are sometimes associated with air conditioning, and indeed can be caused by a poorly designed system. The possible impact on staff of the location of an air conditioning system and its air distribution system should therefore be considered at the design stage.

The height of the ceiling is also important. Manufacturers of air conditioning systems generally state that optimum ceiling height for a direct-vent system should be between 2.70 and 3.50 metres. The cold air, at about 16°C, supplied at this height can mix with the warmer air in the room before it reaches any people, thus avoiding any sensation of cold draughts.

However, if the system does not meet these standards, quality air conditioning systems can always be installed to compensate.

The place of installation, and the height and shape of the ceiling, therefore have a major influence on the presence or absence of draughts. To explain this, here is some information on the properties of cold air. Cold air tends to ‘stick’ to the ceiling for a while before descending. This is called the “Coanda effect”, and allows the cold air to mix with the surrounding air before flowing back into the room.

Unfortunately, the presence of an obstacle such as a ceiling beam will interrupt the airflow. In this case, the cold air will hit the beam and then immediately descend, causing discomfort for the person sitting directly below.

Similarly, if two appliances are installed opposite each other, the cold currents will also collide.

The terms COP (Coefficient of Performance) and EER (Energy Efficiency Ratio) give an indication of the heating and cooling performance level of air conditioning systems. They indicate how much heating or cooling an appliance provides in relation to the amount of electricity required to operate it. Thus, if an air conditioner generates 5kW of heat for an electricity input of 1kW, its COP is rated at 5.0. Similarly, if an air conditioner generates 5kW of cooling for an electricity input of 1kW, its EER will also be 5.0. The higher the COP and EER, the more energy-efficient the appliance is considered to be.

Two forms of heat must be considered in air conditioning:

• sensible heat
• latent heat

Sensible heat

When an object is heated, its temperature increases as more heat is added. This increase in heat is called sensible heat. Similarly, when heat leaves an object and its temperature drops, the heat removed is also called sensible heat. Sensible heat is the heat that causes changes in temperature.

Latent heat

Any pure substance is capable of changing its state. Solids can become liquids (ice turns into water) and liquids can become gases (water turns into steam), but changes such as these require the addition or removal of heat. The heat that causes these changes is called latent heat

However, latent heat does not affect the temperature of a substance: for example, water remains at 100°C when it boils. The heat added to keep the water boiling is known as latent heat. Latent heat is therefore heat that causes a change of state without changing the temperature.

Understanding this difference is fundamental to understanding why coolants are used in cooling systems. This also explains why the terms “total capacity” (sensible and latent heat) and “sensible capacity” are used to define the cooling capacities of a device. During the cooling cycle, condensation forms in the appliance because of aspiration of latent heat. Sensible capacity is the capacity to lower the temperature; latent capacity is the capacity to absorb moisture from the air.