Pacific Fans - Air Movement


What fan do I need?

Before Pacific Fans can answer such a broad question we will need to ask a number of questions of you, such as:
(a) Describe what area you are wanting to ventilate e.g. Home, Apartment, Factory, Warehouse, Restaurant etc, etc?;
(b) What cubic area needs ventilating?;
(c) Is noise a serious consideration?;
There are other issues to consider. It would be best for you to send Pacific Fans a sketch of the area you want to ventilate and we will select a fan or fans or design a system that would best suit your application.

Does Pacific Fans install fans/systems?

Pacific Fans supplies air movement equipment but does not engage in installation of fans or systems. However, we may be able to recommend an installer in your area.

One hears/sees media about HEAT TRANSFER and HOME VENTILATION – what do these terms mean?

(a) Home Ventilation – extracts air from the home through to the outside;
(b) Heat Transfer – transfers the warm air that gathers high up in the home – usually in the attic – and transfers that warm air to other areas of the house.

What is the difference between Ventilation and Air Conditioning?

Sometimes people confuse the meanings of air conditioning and ventilation. Air conditioning means that the air supply to an occupied space is brought to a required condition by cleaning, cooling, heating, drying, and humidifying. Ventilation implies fresh air supply, the removal of contaminants and heat, and air motion for cooling and freshening. In the majority of cases ventilation without air treatment will provide satisfactory air conditions. The essential requirement in ventilation is to replace
contaminated and over-heated air with fresh outdoor air, and to counteract discomfort due to humidity.

What rate of Ventilation is required?

There are a number of factors to be considered, including:
  • Size of room or building
  • Number and type of occupants and their activities
  • Heat gains from equipment and solar radiation
  • Relative humidity
  • Outside air temperature and range of temperature
  • Calculation of air changes per hour for buildings or rooms according to particular characteristics and conditions prevailing
The rate of ventilation can be worked out from these factors, though that is not always necessary. In
many cases it is sufficient to follow recommended rates of air renewal for buildings of various types.
One basis for estimating the rate of air renewal is the number of times an hour the air content of the
building should be replaced with fresh air. The table Air Changes per Hour in the REFERENCE
DATA section of this web provides recommended air changes per hour for various occupancies.

What fan noise levels are acceptable?

This varies according to a number of factors:
(a) The occupancy of the area being ventilated;
(b) The distance the fan is from the occupied zone (people) in the area;
(c) Other background noise;
(d) What acoustics exists in the area being ventilated.
Sound is measured in decibels (dB) and the A-Weighting filter (dBA) is used to simulate what the human ear hears. If you refer to the NOISE DATA sheet in this website you will be able to compare sound level comparisons which are quoted at three metres from the fan without any acoustic barrier. Sound levels published in Pacific Fans product information are free field sound pressure levels at 3m.

Do I need different VENTILATION considerations for the Office area and the Factory area?

Yes, there are essentially two ways of ventilating a building:
• Ventilation by displacement;
• Ventilation by diffusion.
Put simply, Ventilation by displacement is chiefly used to ventilate large industrial or commercial premises, while Ventilation by diffusion is the preferable method for supplying air to occupied zones such as offices and smaller premises.
Ventilation by displacement when properly set supplies large volumes of good air at low velocity into the occupied area to displace the bad air. In using this method it is sometimes difficult to avoid some draught but mostly this is a minor consideration in the overall result.
On the other hand draught can be a major problem in occupied areas, like offices, apartments, hotels, home etc., so Ventilation by diffusion is preferred.
In this method, the supply fan/s should be positioned high to avoid draught and the airflow should be of sufficient volume to flow across the ceiling, or high space, for some distance before falling down to mix with the ambient air

When bringing in cold air to an area, what factors should I take into consideration?

There are a number of factors that must be considered:
(a) Size of area ;
(b) Position of fan/s
(c) Obstacles in path of incoming air;
(d) Where air inlets should be positioned.
These are some factors. Again, it is best to provide Pacific Fans with a sketch of what you want to achieve and we will select fans and/or design a system to meet your particular application.
However, if you are intent on getting the job done yourself you should remember:
Offices, Apartments, Hotels, Homes & Smaller Commercial premises
(1) The Supply Fan/s should be positioned high so that the air flow is directed along the ceiling (or high up if no ceiling).
(2) It is also important that the air stream velocity is right to ensure the air stream flows through about 60% of the area depth before falling down to the occupied zone. Falling too early is less efficient.
Larger Commercial Premises and Industrial Premises
(1) The Supply Fans should best be positioned lower down at lower air velocity directly into the occupied zone

The ventilation system must be set so that air which circulates to the occupied area is comfortable for the occupants of the area.

Is it better to supply air through the ceiling or through the wall?

Generally if is better to supply air from a ceiling diffuser rather than a wall diffuser. This is because the air from a ceiling diffuser spreads in all directions, and therefore takes less time to mix with the ambient air and to even out the temperature.

How do I read the Performance Curves displayed in Product page diagrams?

The horizontal line shows the airflow gradients and the vertical line is the pressure gradient.
Where the curve meets the horizontal line you read the airflow of the particular fan under no pressure and completely free-blowing (maximum air flow).
As the pressure increases the airflow reduces, so the fan’s capacity can be read off the Performance Curve