The quick and easy answer to the question on whether or not you can use an evaporative cooler and dehumidifier at the same time is a resounding NO.
Even though many HVAC or heating and cooling companies claim that it is okay to use both an evaporative cooler and a dehumidifier at the same time, it is not recommended. First, in one sense, they cancel each other out with one adding moisture to the room and the other removing it.
Plus, and a very important point, a dehumidifier will warm the room as it turns electricity into heat energy.
Why Do You Ask That?
You probably realize that an evaporative cooler works best when the air is dry – because it relies on evaporation to remove heat from the air.
An evaporative cooler is a cheap way to cool your home compared to central air conditioning or a mini split system. A dehumidifier is used to take the humidity out of the air, drying the air, and it would seem, make the evaporative cooler more effective.
So, some people would think that if they have both a dehumidifier and an evaporation cooler, then their house will be much cooler and less humid. However, this is not the case. Read on to find out more information.
The Long Answer
As stated above, you should NOT use an evaporative cooler and a dehumidifier at the same time. Not only will this be expensive, due to the electricity that is required to operate both devices, but they will not work with each other to achieve the desired results, cool and dry air. This is because a dehumidifier heats up as it runs on electricity.
If you have ever used a dehumidifier, you know that they get quite warm – exactly the opposite of the effect you’re hoping for by using an evaporative cooler. The net effect of using these appliances together is that your room will get warmer – we say that based on actual experience and what the First Law of Thermodynamics teaches about energy and heat – also called the Law of Conservation of Energy, which states that energy within a system can’t be lost, but it can be converted from one form to another – namely, from electricity to heat in this situation.
Evaporative coolers, also known as swamp coolers, are a cheap, energy-efficient alternative to AC for cooling your home. They capture the moisture from the air, which can cool the air around it anywhere from 5 to 15 degrees, depending on where you live and how large the cooler is.
An evaporative cooler uses electricity – consumes power – to change the water in its tank to vapor – to evaporate it in order to cool the air. They put moisture into the air.
Dehumidifiers do exactly the opposite. They use electricity to turn moisture vapor in the air back into liquid water by condensing it on a cold coil and draining it away.
So, right away we see that they cancel each other out in terms of the moisture vapor and water. And that makes both devices ineffective.
The Worst Part – A Hotter Room
One adds water to the air; the other removes it. But they don’t cancel each other out in terms of heat energy.
When the dehumidifier is running, it converts electricity into heat energy, as mentioned above, and the air around it and in the room gets warmer.
The science behind why it is not a good idea to operate both the evaporative cooler and the dehumidifier at the same time is supported by the First Law of Thermodynamics. According to the law, it is not possible for heat to flow from a colder body to a warmer body without any work having been done to accomplish the flow of heat. Energy will not flow from a low temperature object (evaporative cooler) to a higher temperature object (dehumidifier). Work is necessary for the transfer of heat, and as a result, heat energy is added to the room.
Climate Issues
Where you live will also determine the effectiveness of an evaporative cooler and a dehumidifier. Evaporative coolers are mainly used in the Western United States – areas considered dry or even desert regions. You won’t need a dehumidifier in these parts of the US.
Evaporative coolers are more effective in drier, less humid climates since they take the air and recycle it over a “damp” filter. This cools the air and puts more moisture into the air. Evaporative coolers are not effective in humid regions – pretty much anywhere east of the Rocky Mountains or Mississippi River because the air is already very humid – in other words, it has a high moisture content.
Alternatives
So you want to make your home more comfortable in the warm, humid months. You have a number of other options available, rather than using an evaporative cooler and/or a dehumidifier. The easiest and most cost-efficient way to cool your home is to simply open a window once the outside temperature is lower than the air indoors. Put a box fan in the window facing out to push out warm air. Open a window opposite it to pull in cool air.
If you want to spend a little more, install an attic/whole-house fan. These powerful fans blow up/out, and when windows are open, they pull in cooler outside air. You can effectively lower the temperature of your home by running a whole-house fan during cooler evening and night hours.
The next step up in cooling would be using a window air conditioner or a portable air conditioning system. Both are more expensive than fans, but they cool your home a lot more efficiently. A central air conditioning system or a mini split system is a big expense, but they do a great job of cooling and drying the air in any climate.
Rene,
Your explanation makes sense and of course thermodynamics serve as an experienced judge.
However, what if you install the dehumidifier such that its motor sits outside the room, allowing the heat coming from the dehumidifier to leave the building.