How to Know when to Change Air-Conditioning Filters?

Although we don't usually realize it, we can actually reduce the running cost of a building by removing the dust from the atmosphere. The furniture, walls and fittings are preserved longer. It also improves the health of the occupants.

Removing dust is usually done by installing filters in the incoming air stream or the circulating air stream. In air-conditioning systems, these filters are installed at the air handling units or AHU's.

How do we know when to replace the filters?

As more and more dust accumulates at the filters, the differential pressures between the inlet and the outlet will increase. By measuring the differential pressures, we will have a very good indication of how much the filter has been choked by dusts. Persons maintaining the air-conditioning plant should know at what differential a filter should be replaced. Some of the dust particles are so minute, that they cannot be seen by the naked eye. In all appearances, the filter looks as good as new.

These are some factors to consider when determining when to change the filter:

Mechanical strength of the filter

The final pressure of a filter is usually stated in the product. That is the strength of the filtration medium. However, other factors need to be considered - the strength of the filter walls, frames and holders if not adequately designed can result in the sagging of the filter housing that will result in leaks.

Changes in efficiency of the filter

This is particularly important in low efficiency filters. Their efficiencies can be radically impaired as a result of high final pressure losses. Particles that have been collected by the filter can become detached and accompany the air stream. Fibrous particles are less likely to become detached compared to granular particles. Because of this, higher final pressure drops are permissible for the former, although this should not exceed about 200 Pa in a pre-filter.

With granular particles, the final pressure loss should not be allowed to exceed 100 to 150 Pa.

Fine filters and HEPA filters are less sensitive to changes in quality. In principle, they can be allowed to have a final pressure loss up to the limit of their mechanical strength.

Permissible Air flow variations in the system

In this case, the flow pattern is more important than the particles carried along the air stream. The permissible final pressure loss here will depend on the total pressure and characteristics of the fan and any other control facilities.

The filter will affect the air flow as a result of dust accumulation. The filter has to be changed when the velocity of the air in a laminar flow installation cannot be maintained or has fallen below the required specifications.

Bacteriological reasons

Sometimes, the filters are replaced at regular intervals instead of pre-defined pressure loss indications. This is to prevent accumulation of bacteria and other microorganisms.

Suitable time window periods

Filters are often changed to coincide with pre-planned plant shutdown periods. In these cases, production disturbances are minimized. For example they can be arranged to be changed during holidays.

Economic considerations

In terms of operating costs, there is an optimum final pressure point to balance. By having longer intervals between filter replacements, we do achieve lower filter replacement costs. On the other hand, this will increase the operating energy costs due to inefficiency.

About The Author
Thomas Yoon
Many years of working experience in Marine, Facilities, Construction has given the author material for writing e-books and articles related to engineering, and management. Subscribe to facworld ezine by sending an email to mailto:facworld-subscribe@yahoogroups.com. More information at http://www.free-marine.com and http://www.free-engineering.com

Cool Air

Summer’s coming and things are of course getting hot. It is time to cool your homes and work places with a new air conditioner or swamp cooler. Along with air conditioning and swamp cooling, however, come higher energy costs. Conservationists suggest planting trees around your house or office to cool it with the shade. This will save you money on your energy bill, and keep the place nice and cool. For those who do not have the option of planting a tree to cool off in the shade, or who do not have the time to wait for a tree to grow large enough to cover them in shade, there are more efficient air conditioners and swamp coolers. It may be worth it to do a little research to find a more efficient air conditioner for your home or office; one which cools a larger area for a lower cost.

Air conditioners have a standard energy efficiency rating or EER. Air conditioners are often rated by the number of British Thermal Units (Btu) of heat they remove per hour. Almost all new air conditioners will come with and/or be advertised with ratings of their cooling and energy efficiency in the measures noted above. You will need an air conditioner that will sufficiently keep a room cool while using as little energy as possible. A number of factors can affect a rooms temperature, including the size of the room, the height of the ceiling, the insulation in the walls and the ceiling, heat generated by appliances and occupants in a room, and as noted before, whether the home, room, or office you are attempting to cool is shaded or in the sun.

There are two main groups which publish calculation procedures for sizing air conditioners for your room, home or office: the Air Conditioning Contractors of America (ACCA) and the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE). Air conditioner installation contractors often use these standard measures when installing air conditioners in buildings and homes. You can also use them as you select and install the most efficient air conditioner for your home or office.

Just as a number of factors influence the heating of a room, home, or office, a number of factors affect the efficiency of your air conditioner or air conditioning system. Each air conditioner will come with a description of how many Btu per hour are removed for each watt of power it requires. Generally, however, the larger the air conditioner, the more energy it requires. A larger air conditioner may cool a room faster, but it will reduce efficiency because it turns off and on more often. This can wear down an electric air conditioner more quickly as well. It also causes more demand on the electric generation and delivery system to the air conditioner.

So, if you cannot shade your house, room or office with a tree, perhaps you should consider keeping them cool this summer by investing in a more efficient air conditioner. Keep your home or office cooler, while keeping your bills low. Find an air conditioner that is not so large that it creates unnecessarily excessive costs to run, and which will keep the room cooler, more efficiently. Do your research, and be sure to check the Energy Guide Label, which must be attached to all new air conditioners.

About The Author
Peter Jay is a Search Engine Marketing professional for Air Conditioner Home. To learn more about air conditioners, swamp coolers, humidifiers, or evaporative coolers, visit http://www.air-conditioner-home.com.