Keeping it cool: How to maintain fan and pad cooling systems

Cooling season is here and with it, fan and pad cooling systems, the most popular for greenhouses, are going to be put through their paces. Much like going through the winter heating system with well-tuned boilers or unit heaters, the effectiveness can wane. The information in this article is not going to focus on correct design of systems, such as ensuring there is adequate pad area or that there are enough fans of the appropriate size. Rather, this will focus on evaluating the components of your system (such as fans, pads and control systems) to ensure effective cooling for your crops.

Before water starts running though pads, exhaust fans are used to remove warm air from the greenhouse. First, make sure that nothing is obstructing the exhaust fans inside or outside the greenhouse. This will reduce the efficiency and effectiveness of fans and put more wear and tear on them. A good rule of thumb is to keep the equivalent of the fan diameter clear, both indoors and outdoors. Additionally, sealing any cracks around fans will help keep the air flowing through exhaust fans efficiently. There are numerous moving parts on exhaust fans, including shutters, bearings and belts. Lubricate shutters and bearings to ensure they move freely and replace any parts that don’t move freely following treatment. Similarly, if a fan belt looks compromised, replace it.

Pads are the other primary component of these cooling systems that require care and maintenance for maximizing their cooling capability. Like exhaust fans, the correct airflow through pads are important. Keep the area around pads on the interior and exterior of the greenhouse free and clear to maximize airflow through the pads. Seal any cracks that surround the pads, as these will reduce the volume of air coming into the greenhouse through the pads. In addition to sufficient airflow, ensure a sufficient volume of water is being delivered from the sump to the pads. If waterflow is insufficient, it will diminish the effectiveness and efficiency of your cooling system.

Over time, build-up can accumulate on the surface of the pads. This includes solutes in water resulting from hardness, as well as other contaminants. Since the water in an evaporative cooling system is captured and recirculated in the system, start with the best possible water quality. As water evaporates and is captured, contaminants will start to concentrate in your water. Regularly bleed off the water in your sump and top it up with fresh, clean water. Periodically replace the water entirely in your sump.

Algae should also be minimized in any fan and pad cooling system, and there are a few ways to work towards this.

First, continue to run exhaust fans with the sump pump off and no water running to pads at the end of the day. This will help dry out the pads and reduce algae development on the pads themselves. You may be able to treat water to keep algae loads on pads, but ensure any additives are not harmful to plants — some are intended for use when there are no plants. Additionally, shade the sump to reduce light entering the tank which could promote algae growth.

The sensors that monitor the greenhouse environment and help control cooling systems are another essential component the systems. Put any sensor measuring air temperature at the height of the plant canopy, but not necessarily at that of eye level for greenhouse personnel. Periodically clean and calibrate sensors as they, like other types of sensors, can drift over time, reducing the accuracy of air temperature management.

Any system needs maintenance for optimal performance, and fan and pad cooling is no exception. Periodic and preventative maintenance will keep systems performing their best for your plants, and no grower — or greenhouse — will need to lose their cool.