Evaporative coolers are also called swamp coolers. In this article we will be talking about the How’s, What’s, and When’s.How do they work? When is the best environmental range for them work in? And what should you do to maintain them?
First, let’s discuss: How does an evaporative cooler or swamp cooler works?
To understand how a swamp cooler works, we will discuss our sweat, yes our sweat. Sweating is the way our body naturally cools itself. When our body sweats it creates a sheen of moisture over the skin. When air moves over our sweat, it evaporates. That process causes a heat exchange that benefits the body because heat is transferred from the body to the evaporated sweat. That process lowers the body’s temperature. That is the same way that a swamp cooler works.
Swamp coolers are not new inventions. Leonardo da Vinci is credited with the invention of the first hygrometer and the first mechanical air cooler. Since da Vinci there have been many individual studies and discoveries that have contributed to the commercial application of the evaporative cooling system. Discoveries by Blaise Pascal (Pascal’s Rule for Liquid Pressure), Robert Boyle (Boyles Law – 4 principles of evaporative cooling), fluid dynamics by Bernouli, Euler, Chezy and many more have contributed to the evaporative cooling commercial design and success.
The main parts of an evaporative cooler consists of the main box, duct work (unless a window cooler), the motor and belt, the fan blower, the water pump and float, the water distribution system, and the cooling or evaporative pads. Each of these parts makes the whole system that is a swamp cooler.
The swamp coolers operation is simple. The water is kept at an appropriate level in the water reservoir in the bottom of the swamp cooler box. That water is pumped through the water distribution system to trickle down the cooling or evaporative pads. As water is trickling down the pads the motor is turning the blower drawing air into the box and directing it down the duct work into the home. As water is trickling down the pads some is evaporating. The float operates a water valve to keep the water at an optimal operating level.
What are the operating conditions that allow an evaporative cooler to work?
Take a look at the table below, it gives a better idea as to why sometimes it feels like they are working and other times it does not.
The higher the relative humidity levels, the less effective the swamp cooler becomes. At some point the humidity levels become so high a swamp cooler has no appreciative effect on the environment we may be trying to cool.
Why would some have a swamp cooler?
First, because they live in an arid location where humidity levels are relatively low. Second, is because of cost. One study showed that a 1,500 square foot home could save as much as $1,100 annually verses an air conditioner. Additionally, repair and service costs tend to be lower for swamp coolers than air conditioners.
So how do we maintain them?
Let’s first talk about start up and routine maintenance. Cooler pads should be replaced at start up and at the midpoint of the cooling season. Pad replacement should be dictated by the mineral build up from your water supply; pad replacement could be more often if there is a lot mineral build up in the system. When replacing the pads be sure to wash the frames and retainers to remove scale build up and dirt. During the start up and pad replacement, you should check the blower motor belt for wear and tension, adjusting or replacing as needed. When looking at the belt, inspect it for cracks and/or unusual wear patterns and replace as needed. Tension is generally checked by pushing on the belt. It should give about one inch with normal pressure, but you should always check the manual for proper tension. Finally, check and grease or oil the blower bearings.
At the end of the cooling season you will want to winterize it. This maintenance is important to protect the device and also to prevent mold from growing and developing.
The system water should be shut off and the reservoir and water supply line drained. To drain the reservoir and water supply lines just attach a hose to the drain and drain off the side of the roof, this will avoid depositing minerals on to the roof system. in addition remove the stand pipe, drain, and clean the system. (Some water reservoirs can be damaged by additives or cleaners, mild soap and water is your best option) The pads will dry out naturally on their own, you will replace the old pads at the beginning of the next season. Once the system is cleaned and the pads have completely dried out you can place your cover on the unit. A cover will keep wind from going through the system and into the home and protects it from the sun.
As for any system, you should read and follow the manufactures recommended maintenance routine. If you cannot find any maintenance documentation, have it serviced by an HVAC professional and follow them through the annual maintenance routine. This will help you to decide if it is a process that you can perform yourself and allow you to become familiar is the system before doing maintenance yourself. When calling and scheduling an HVAC professional to perform the work, ask to make sure they are comfortable with your following them through the process.
As an inspector what am I looking for when examining a swamp cooler?
I am first looking for how well maintained the unit is. Is there scale build up? Do the pads look like they are changed on a regular basis? Is there any rust that needs to be addressed? Do the sides easily detach and reattach to replace the pads? How is the water run to the unit, through the roof or over the roof surface? Is there any evidence of leaking? What does the belt, motor, and blower look like, are they in good condition? Does the unit work correctly? Are there any sounds that are not “normal” to its operation?
When would an inspector not inspect a swamp cooler?
If the unit has been winterized and is covered, we will not inspect it. If there is any evidence that one of the questions above is answered in a way that could possibly causes more damage to the home or the unit, we will not operate it. All our findings will be documented in the inspection report for you to consider with your broker or to add to your decision making process. In some cases we will recommend evaluation by an HVAC professional.
Understanding how a swamp cooler works and the maintenance it needs is the first step in helping it last longer. A swamp cooler can save you money and be an easy way to stay cool in the summer months. But, as with all things, they do need regular maintenance. This is something that you can easily do that yourself or have a professional perform the work for you.
By Jeremy Strouse 7-24-2017