For anyone living in the Southwest where summers are hot and dry you must be familiar with "Swamp Coolers" . For those of you who have not been to the Southwest, when you do, you will see many buildings - from small homes to large commercial warehouses- with some strange looking boxes sitting on the roof of the buildings.
Those boxes are swamp coolers. A swamp cooler provides a very efficient and low cost of cooling down a living or working space. It cools down outside dry hot air by means of water evaporation.
While swamp coolers may differ in design and size, they all operate under the same principles: water is trickled or sprayed over a high surface area material and air is pushed or drawn across that media. As the hot-dry air comes in contact with the wet surface of the media it causes some of that water to evaporate.
The image on the left shows a cutaway view of a conventional evaporative cooler, the most commonly found in the Southwest. Inside is the fan and fan motor, the outside covers house the Aspen pad media, on the front lower corner the recirculating water pump and make up water and float valve are seen.
This is one of the larger size units, it is about the size of a walk-in meat locker.
The entire front end is the air intake. Inside a large wall of evaporative media is sprayed with water to create a wet wall where evaporation takes place (picture to the right).
In order for water to evaporate energy in the form of latent heat is required. This heat comes from the air going through the media, as the air gives away heat to evaporate the water two things take place: the temperature of the air is dropped, and the relative humidity of the air going through the media is increased.
This type of cooling can only be used in dry climate zones where the difference between the wet bulb and dry bulb temperature of the air is big. In humid places like Chicago or Washington DC where the relative humidity is high, this type of systems would not work at all.
There are different versions as to where the name "swamp cooler" comes from. Some people say it because of the "muggy" or "swampy" feel that the humid air gives to living spaces. Other people refer to the "swampy" smell associated with these units. That swampy smell is caused by bacteria growing in the evaporative media in the coolers.
Swamp coolers are strongly connected with the history of Zeta Corporation for it was one of our very first applications that we targeted when the company was formed. Swamp coolers may have many advantages over refrigeration units (air conditioners) such as lower cost to operate, easy for the average home owner to maintain, low replacement cost, and add some moisture to the dry desert air, they do not come free of problems.
Main problems with swamp coolers is related to the water quality usually found in places where the units are best suited for: the desert. In arid places, water tends to be relatively hard (see previous post on water hardness) . The hardness in the water can cause severe scaling problems in the evaporative media of the swamp coolers, and the bacteria in the media give away that unpleasant "swampy" smell.
Problems with swamp coolers:
- Scale formation on the evaporative media will reduce the airflow across the pads, thus reducing the cooling efficiency of the unit. In some places the scaling takes place so fast and it is so severe that pads need to be replaced several times over one cooling season. The picture to the right shows the pads of an evaporative cooler in the Tucson area. The pads were completely scaled over in a period of three months of continuous use.
- Evaporative cooling pads, because of their materials of construction cannot be cleaned out, once scale has formed on them they have to be discarded.
- Scale in the pump impellers that distribute the water to the pads can cause the pumps to burn out. This can be an expensive problem especially for large warehouses where multiple units are used.
- Scale can also form on the fan motor, causing it to fail, again, an expensive problem in large warehouse operations.
- Scale buildup in the spray nozzles or drip tubes will prevent water from reaching all the media, creating "dry spots" which allow hot air to pass through the media without any cooling, thus reducing the cooling efficiency of the unit.
- Bacteria growing in the media not only causes the unpleasant "swampy" smell, but can also represent a potential health hazard by harboring pathogens that could cause respiratory diseases like legionella.
So how come there is not much being done to prevent these problems? It seems that most people have just resigned themselves and accepted them as inconveniences inherent to the use of swamp coolers, something that "people have to learn how live with" perhaps. Because most of the replacement costs are relatively small, at least when looked individually, people tend to just include them in their maintenance budget. The problem is that when there are multiple evaporative coolers in one building, or large size units are utilized, the replacement costs do add up.
The Zeta Rod has demonstrated time and time again that it is capable of stopping these problems in a very cost efficient manner. A single Zeta Rod (properly sized) installed in the main water line going into a building, whether it is a small home or a large commercial warehouse can treat all the water that goes to the swamp coolers and prevent the problems mentioned before. Because the water volume being held in the evaporative coolers is so small, and the evaporation rate so high, this ensures that a constant stream of fresh Zeta treated water is being added to the cooler. With its strong electrodispersant effect the Zeta Rod prevents scale deposits from forming on the media, pump impellers, fan belts and motors, spray nozzles and drip lines. It also prevents the bacteria from growing in the media, thus eliminating the "swampy smell" and the potential for unwanted bacteria growing in the media.
Benefits offered by the Zeta Rod:
- Scale formation and odor in the evaporative coolers is eliminated.
- Elimination of scale in nozzled and drip lines
- Extend lifespan of Aspen pads to 2-3 years, and indefinitely on Celdek type pads.
- Service life of the cooler and frame is extended by 50% or more.
- Water consumption can be reduced by as much as 25% while maintaining the full efficiency of the cooler.
- Short ROI based on maintenance, operation and water cost savings.
- Low maintenance required.
Our customers include the Research Greenhouses at Biosphere 2 where old evaporative pads in the greenhouses where about to be replaced due to the heavy scaling and biofouling formed on them (read the case study for Biosphere 2 here).
This picture shows the Zeta Rod installed in the recirculating line for the wet wall at the Biosphere 2 Research Greenhouses. In this case, the Zeta Rod cleaned the deposits formed on the evaporative media, allowing Biosphere 2 to extend the use of the expensive media an additional 7 years until the greenhouses were put out of operation.
The Pepsi Bottling Plant in Tucson, another satisfied customer, has this to say about their Zeta Rod :
"For over three years now the Zeta Rod has proven to be an excellent choice as our water treatment program.
The first installation in our evaporative coolers eliminated the scale, odor and deterioration of our units. The coolers have operated scale free and odor free. Pads last a couple of years now, whereas before the Zeta Rod was installed it was necessary to change them twice per season. Our maintenance costs are much lower now since we are not losing any recirculating pumps in the coolers due to scaling. "
(picture to the right shows the Zeta Rod installed in the plant's main water line where the feed to the swamp coolers takes from)
This is a good time to start planning for next year's cooling season and how to protect your swamp coolers. You can contact Zeta Corporation directly, or one of its authorized distributors to ask about a Zeta Rod for your swamp coolers.
