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Equipment designed for challenging environments such as greenhouses and indoor farms face the constant threat of dirt and moisture ingress due to exposure to humidity and wet conditions caused by maintenance, rain, and irrigation. Horticultural lighting products in particular can be negatively impacted by ingress of moisture and dirt which severely impact the performance and longevity of the product. In many cases, ingress of dirt and moisture happens despite the equipment manufacturers best intentions- such as sealing an equipment enclosure with air and water tight seals and implementing IP 5x or 6x ingress protection. So what goes wrong here?
Ingress happens when atmospheric pressure changes act on a sealed equipment enclosure. As the pressure changes, a small amount of positive or negative pressure develops inside the enclosure. These atmospheric pressure changes can cause a daily shift in the differential pressure between the enclosure and its environment. When negative pressure develops inside the enclosure – due to increasing atmospheric pressure – a small vacuum is formed inside the enclosure. Over time, the daily shifts in atmospheric pressure also cause wear and tear on enclosure seals. If a seal becomes compromised at any point due to stress, vacuum pressure inside the enclosure will draw moisture and dirt into the enclosure.
Standardized tests for ingress protection can be performed informally by the manufacturer or can be performed by a certified third party lab. Ingress protection ratings are classified by ISOXXX, and involve a two digit rating, where the first digit classifies the dust ingress protection, and the second digit classifies the liquid ingress protection.
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We should note here that these tests are typically done once, in absence of cyclic changes in atmospheric pressure and normal wear and tear. Further, these tests typically won’t catch ingress of water vapor, which can later condense into liquid water, causing condensation and damage. Water vapor can also penetrate joints, seals, and materials much more effectively than liquid water since it lacks the surface tension of liquid water.
Based on our experience working with horticultural equipment and lighting, GrowFlux believes the best design practice for ingress protection is to consider the challenges presented by changing atmospheric pressure, wear and tear, material performance over time, and water vapor ingress. In designing its horticultural lighting product line, GrowFlux has employed several design features to boost our ingress protection:
Pressure equalized enclosures
Mitigating differential pressure in an enclosure is easily achieved by designing in a specialized vent which allows only a small amount of air to pass while blocking moisture and liquid water. Not everyone in the industry is doing this as it increases cost and assembly complexity, however in our experience protective vents pay for themselves. The protective vents we install in every product with a hollow enclosure incorporate PTFE fabric at the core, passing only the amount of air necessary to remove pressure from sealing gaskets. These vents are also commonly installed in high quality LED street lights.
Fully potted power supply
Our FluxScale Series fixtures use the Meanwell HLG AC/DC driver, which offers the highest efficiency of any 300-600W driver we have seen on the market. This driver is also fully potted (or filled) with thermally conductive, high temperature silicone which protects the electronics inside the driver from water, dust, and moisture while also dissipating the small amount of heat created by the driver – resulting in its high efficiency. These drivers were originally developed for stadium lighting applications, and are well suited to challenging agricultural use.
Gasket material selection
Gaskets, O-rings, and other compressible seals can be made of a wide variety of materials. Proper material selection and extensive design for manufacturing is critical to maintaining ingress protection in a seal; designers must consider manufactured part tolerances, material properties at operating temperature, degradation mechanisms in the seal materials, and the sealing material's ability to resist permanently compressing over time (called compression set resistance), among other factors.