Keep lower temperatures in your greenhouse or grow room in any climate with cost-effective evaporative coolers. Evaporative coolers, sometimes called swamp coolers, use water to reduce temperatures without using a lot of energy.
In dry climates, evaporating water into the air provides a natural and energy-efficient means of cooling. By passing outdoor air over wet pads, the water in the pads evaporates. This has a cooling effect of 15° to 40°F before it is directed into the home or grow room. As water evaporates into the air, energy is lost which causes the air temperature to fall.
The normal air temperature we can measure with a standard thermometer is the dry-bulb temperature. The wet-bulb temperature is more complex but means the lowest temperature you can achieve by evaporation of water only.
This is linked to the moisture content or humidity of the incoming air. The wet-bulb temperature tells us how much cooling is possible. It’s based on the temperature and relative humidity level of the incoming air.
The more humid the air is, the less cooling can happen because it reduces the amount of evaporation. Wet-bulb temperatures these days can be easily measured onsite using humidity meters which can display wet-bulb temperatures.
It is important to remember the cooled air will gather heat as it circulates in the growing area. Heat build up depends on many factors. Some include how far the cooled air travels inside the growing area and heat output from lamps and other sources.
It is possible for the temperature build-up inside the indoor garden to reheat the circulating air. Sometimes hotter than that of the outside environment. Fix the amount of evaporative cooling and amount of air to be vented in and out need to be done correctly.
Ventilation is an essential component of evaporative cooling. As water evaporates, cooling the air, humidity goes up. Higher humidity can create problems for plant growth by slowing transpiration and increasing disease. Humid air needs to be vented out at a sufficient rate to keep relative humidity down below 89-85 percent.
Windows are partially opened to allow warm indoor air to escape as it is replaced by cooler air. Evaporative coolers provide a steady stream of fresh air into the house unlike central air systems.
In climates with high outdoor humidity, evaporative cooling can’t be used. In this situation, air conditioning units are a good alternative and can also lower temperatures much more when needed. Air conditioning does produce relatively dry air, though. This is where a humidifier would be perfect.
Evaporative coolers cost about one-half as much to install as central air conditioners. They use about one-quarter as much energy. However, they require more frequent maintenance than refrigerated air conditioners and they're only suitable for areas with low humidity.
Sizing and Selection
Evaporative coolers are rated by the cubic feet per minute (cfm) of air that they deliver to the house. Most models range from 3,000 to 25,000 cfm. Manufacturers recommend providing enough air-moving capacity for 20 to 40 air changes per hour, depending on the climate.
Generally, most Evaporative coolers you see are window mounted, but portable swamp coolers are a great alternative! These are perfect swamp coolers for grow tents.
Drawbacks of Evaporative Coolers
Evaporative coolers should not be used in humid climates because they add humidity to the air in your home. Also, they do not cool your house down as low as an air conditioner would. They also require simple maintenance about once a month.
If the evaporative cooler is installed on the roof, routine maintenance can cause some damage. A sunlit rooftop cooler will be about 1°F less effective than a shaded cooler. Rooftop maintenance also requires using a ladder, which may be hard.
By their nature, evaporative coolers always use water. In areas with limited water supplies, homeowners may be concerned about the water-use impact of adding an evaporative cooler.
The Parts that Make Up an Evaporative Cooler:
Water Supply Valve
This valve is found inside of your home, generally where your water heater is connected to the rest of your plumbing. This valve is connected to your swamp cooler by a copper tube. It brings water into the swamp cooler. Without this valve, the swamp cooler cannot work.
Float
The evaporative cooler float is found on the bottom of the swamp cooler. The float rises on top of the water and shuts off the water supply valve when the set limit is reached. If this float stops working, the swamp cooler may not work or may overflow.
Pump
The swamp cooler's pump is also found on the bottom of the unit. It pumps the water through the water lines, keeping the evaporative pads wet.
Evaporative Pads
The evaporative cooling pads line the inside of the swamp cooler. They have to be wet for the swamp cooler to work properly. They clean and cool the air.
Blower and Blower Motor
The blower motor turns the blower. This brings cool air into the ductwork and forces it out of a room, cooling the air.
How Does a Swamp Cooler Work?
A swamp cooler works to cool the air in your home with four main steps. These are:
Water Supply Valve Brings Water into Bottom of Swamp Cooler
The water supply valve brings water into the bottom of the swamp cooler. The water continues to pour into the swamp cooler until the float reaches a certain level. The float sits on top of the water. This signals the water supply valve to turn off.
The Pump Brings Water to the Evaporative Cooler Pads
The pump begins to pull water through the water distribution lines once the base is full. These water lines are located at the top of the pads and pour water through them. You can turn the swamp cooler's switch to "pump" to pump more water into the pads for more cooling power.
Warm Air is Pulled Through Evaporative Cooler Pads
The blower motor begins pulling warm air into the swamp cooler after the pads have water on them. As the warm air goes through the pads, the moisture cools the air, and cleans it.
This process is called evaporative cooling. This works the same way when you sweat and then have a fan blow on you. This cools your skin.
Blower Forces Cool Through Vent, Cooling Home
The blower takes the cooled air from the pads and forces it through the ductwork and vent, and into the house.
