I purchased an evaporative cooler from one of the big box home & garden stores, and installed it on the northeast side of my greenhouse. It sat on a concrete block pad (I placed/leveled a few concrete blocks on the existing dirt ground) outside the structure. I also attached it to 2 hanging chains/hooks for additional support. The unit's cooling outlet poked through a small side window into the structure. The water resevoir (on the outside) was automatically refilled using a floatation on/off device connected to a tube which connected to my greenhouse water faucet. I did have some issues with the tubing leaking at the stepdown connection (from garden hose size hose to 1/4 inch tubing.) I have a greenhouse controller connected to an outlet specific for "cooling" and just plugged the evaporative cooler's electric plug into the special outlet. My controller was able to turn on/off the unit (by supplying power or removing power from the outlet) as needed with my set temperature requirements. It probably brought the temperature down by 10 (maybe 15) degrees at most. It also blew cooling/humid air which was a nice benefit--the plants in its direct path were cooler than the ambient temperature. Unfortunately, algae grew in the resevoid and the unit's pump it died after the first winter (likely froze since the resevoid was outside the structure) even though I attempted to weatherize it (guess my weatherization wasn't effective.) After it died, I just left it in place, but covered it on the inside with plastic to prevent cold air leaks in the winter. It was rather inexpensive to purchase and to operate. And, because I was able to self-install (and I'm very much NOT an HVAC installer type) I am considering another one to replace it.

Hey how are you ? If I remember right you have a fogger for your greenhouse .Most of the ones I have seen are too big for my 12 X 24 . I have been using an under bench mister with a fan blowing thru the mist the exhaust fan pulls up the cooler air without wetting the plants . The advantage of a swamp cooler over what I have would be too hook it to a thermostat. Thanks for the reply :) Gin

What are the benefits of using a Portable Evaporative Cooler? – Super Energy Efficient: Using portable air coolers is very cost-effective to cool your place without spending much money on electricity. Swamp coolers cost up to 50 percent less than air conditioners that use refrigerated cooling systems. Imagine that, a 36-inch swamp cooler working for 8 hours typically costs you less than $1! Because the operating costs needed are only for water and electricity. Even some swamp cooler designs don’t need any electricity. – Zero Emissions Since the system leaves a low level of carbon footprint, it produces no emissions. Unlike other traditional cooling systems, the evaporative cooler has no refrigerant gas or compressor. Furthermore, it releases no toxic chemicals in the air. Swamp cooling systems use no refrigerants that potentially harm the environment. Most refrigerant chemicals used in air conditioning systems deplete the earth’s ozone layer. As a result, they cause global warming to occur. – Prevent of Air Pollution The cooler is fitted with a filter to help filter out odor-causing pollutants and dirt from the indoor atmosphere. Consequently, the quality of indoor air in your rooms will be improved significantly. Apart from being eco-friendly, the cooler additionally safeguards the rooms of your home from air pollution. The Airy Plant is yet another highly innovative product widely used to purify air in an efficient way without energy. – Portable and Practical You can easily drag the cooler to any room. You can also pack the device easily, as it was designed to be moved around effortlessly. – Cost-Effective Setup Unlike the traditional air conditioners, you can set up your portable evaporative cooler in an inexpensive way. These systems are cost-efficient considering there is no need to set aside any amount for installing the device. You can buy the evaporating cooler from the online stores and simply install it in any of your rooms. After a certain period has elapsed, it is recommended that you clean the water tank, the motor, and filter components. Thankfully, you can perform the tasks with no prior expertise or experience. – Adds Moisture The evaporative cooling devices boost the level of moisture inside your home. Therefore, if you live in a region that experiences dryer climatic conditions, the cooler will come in handy. The standardAC systems have a major downside. Unlike the evaporative cooler, the traditional AC units take out moisture from the environment indoors. Note that eliminating moisture from the indoor atmosphere potentially causes breathing difficulties. Furthermore, it is likely to cause cracking or drying of skin. 3. Is there any shortcomings of using Evaporative Air Coolers? – Since Evaporative Cooling Systems increase the level of humidity inside homes, do not use them in areas of humid climates. When compared to the traditional AC systems, Evaporative Coolers cool down your home to higher temperatures. Moreover, they require basic maintenance at least once every month. – Portable air coolers are designed to use water continually. In the locations having limited supply of water, homeowners might be wary of adding the cooler considering their water-use impact. – In areas experiencing low-humidity, evaporating water in the air allows homeowners to enjoy a highly energy-efficient and natural cooling method. Swamp Coolers work using this concept. These coolers cool the exterior air by letting it flow over water soaked pads. This, in turn, causes water in the pads to evaporate in the cooled air. The cooler air which reaches temperatures of between 15 °F – 40 °F is then guided into the house. The warmer air, on the other hand, is pushed outside through the windows.

I just read your post again and in regards to the existing wiring, it looks like you may have the necessary wiring in place, although of course the grounds are still an issue. If the black & white is your line side, the switched load side maybe something like red/black for low/high on the blower and orange for the pump, with the white neutrals tied together in the box. BUT, you need to verify this at the cooler first! Don't know what the current switches look like but below is an example of a single gang swamp cooler replacement switch available at Home Depot. Here is a link that might be useful: Replacement swamp cooler wall switch at HD