The elections are over and marijuana was the winner in some states. Voters in California, Massachusetts, and Nevada legalized recreational marijuana initiatives and many other states approved medical marijuana use. As the movement to legalize marijuana continues to take hold across the country, growers are beginning to seek out equipment that will help them maximize production. Until recently, there were no cooling and drying products specifically designed to optimize growing conditions for this agricultural product. Now, new technology is being engineered that can produce the right temperature and humidity conditions to maximize productivity and minimize mold and insect problems. Century Refrigeration has partnered with other companies on custom systems that increase product yield while reducing water usage and eliminating the need for a variety of other equipment.



Legalized marijuana is creating somewhat of a gold rush, as equipment manufacturers begin to venture into a market long in the shadows. Many growers have been turning to design-build contractors to provide cooling and dehumidification systems to help them maintain the temperature and humidity conditions needed for the various phases of marijuana grow operations. For example, growing temperatures should be kept at 77° to 80°F to produce the largest yields, while humidity must be tightly controlled during drying operations. The cooling demands are based on how much light enters the building; most buildings tend to experience outdoor heat infiltration.  

Century Refrigeration, located in Pryor, Oklahoma, has been involved in produce and agriculture storage for many products, including Vidalia onions, tomatoes, potatoes, bananas, apples, and even pecans. These applications often require customized, rather than standard, off-the-shelf units.

“We take pride in our ability to work closely with a wide variety of agricultural applications,” said Dave Nichols, sales engineer at Century Refrigeration. “Working with growers to determine their temperature and humidity requirements, as well as serviceability needs, we then design systems for specific applications and requirements.”

To respond to the emerging niche market for marijuana cooling equipment in the Pacific Northwest, Century Refrigeration experts partnered with refrigeration equipment designers who, in the past, focused on salmon hatcheries and other produce warehouse storage. These experts say the difference between air conditioning and refrigeration is huge, and this difference has an enormous impact on marijuana grow operations. In an air conditioning-based system, an HVAC contractor installs one or more large air conditioners, typically sized for an office space, and then installs ductwork that simply recirculates the air. The air conditioners attempt to maintain the optimal temperature. Humidity is handled by pairing the air conditioners with either off-the-shelf or custom made dehumidifiers. For example, a 100-light application might require 10 large air conditioners and as many as 30 large dehumidifiers.

Problems arise because the air conditioner and humidity components are installed separately, and the two systems don’t communicate with each other. This is especially critical at night; when the lights go off, the humidity rises to very high levels. When the humidity is too far off, the plants can grow mold or become infested with spider mites. Another problem is the sheer cost of the dehumidifiers, including equipment, plumbing, and wiring costs.



Using a systems-based approach, Century Refrigeration has worked with equipment designers to develop an efficient solution tailored specifically for the rapidly emerging marijuana growing industry.

The turnkey systems control both daytime temperature and nighttime humidity. The number and size of the units can be customized based on the refrigeration load. It can be tailored specifically to the number of grow lights, the number of watts per light, the amount of light infiltration, and the facility size. Systems have been developed for smaller grow operations with 50-500 lights, as well as numerous larger operations with as many as 1,875 lights.

Marijuana growing operations begin with a veg room, where lights are on for the majority of the day. These are LED lights that don’t give out a lot of heat. The plants are then placed into bloom rooms equipped with custom-built, application specific systems manufactured by Century Refrigeration. These rooms operate with lights that circulate on and off, a cycle that tells the plant it is time to bud. The plants are bloomed for approximately 56 days. They are then harvested and placed in a drying room, where humidity must be controlled both day and night. For ideal drying conditions, the rooms are kept at a constant humidity and 70° air temperature. Century provides custom circuiting and controls, which are needed to maintain the required temperature differential (TD) for the application. Century offers three different sizes of equipment, depending on the size of the application.

Century Refrigeration has been a long time supplier of equipment for numerous large cold storage projects for potato farms and strawberry growing operations. For the marijuana application, they went through many rounds of engineering to develop the custom-circuited coils and also developed a line of condensing units with warming features required.

The design is similar to other solutions developed for products needing a controlled environment – just a bit warmer. In fact, some refer to it as a beer cooler. For example, a classic beer cooler temperature is about 35°. The coolant is run at around 25°, so there is a 10°TD. By contrast, the marijuana units are set to run at a much higher temperature, and the refrigerant is run at 45°, making for a larger TD. Reliably maintaining such a large TD between the refrigerant temperature and the desired cooling temperature requires the special circuiting developed by Century Refrigeration.

The custom circuitry includes evaporator coils that provide the system dehumidification. The custom coils allow the system to condense water from the humidity and use the recovered condensate to water the plants. Using the recovered condensate water significantly reduces water requirements and costs, another big plus. It also eliminates the need to purchase separate dehumidifiers.

For example, one customer considering the classic air conditioning solution would have had to purchase 27 dehumidifiers at a cost of $6,700 each, for a total cost of $178,000. By selecting the refrigeration/dehumidification system using Century technology, they avoided that cost.



As marijuana legalization efforts take hold across the country, growers are looking for top-quality cooling and drying technology to ensure high-volume production. Using application-specific systems, like the one developed by Century Refrigeration, is one of the most efficient options available. In fact, growers using the new system with Century Refrigeration equipment report that crop yields have increased substantially compared to air-conditioning systems, with zero loss to mold and spider mites.

Publication date: 4/17/2017

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