Outdoors, or in wet indoor environments like wash-down areas, Low Humidity Control Cabinets of electronic systems begin with the style of the enclosures and penetrations, and end with the design and configuration of the components. This article focuses on a number of these best practices.
Assume your enclosure will leak. Unless the application demands a vented enclosure (e.g., for heat dissipation, battery off-gassing), a sealed enclosure represents the very first line of defense against moisture. Unfortunately, even the most effective NEMA 4 electrical enclosure works great until poor installation practices or out-year modifications create poorly sealed penetrations (Fig. 1).
It’s advisable to believe that penetrations into any enclosure are going to leak (as shown by Fig. 2). Based on this assumption, top-mounted conduit penetrations where moisture can collect on horizontal surfaces needs to be avoided. Even if Myers hubs or sealing locknuts are being used for code compliance, enclosure penetrations needs to be made below energized parts, whenever possible.
When it comes to cable penetrations (versus conduit penetrations), directing water from the electrical enclosure or housing by using drip loops (Fig. 3) is an additional best practice. The next step is to heat-shrink the connector fittings and alternate wrappings of electrical tape and butyl self-adhesive rubber tape to protect against moisture intrusion to the connector.
Maintaining door seals is incredibly important. Door seals ought to be inspected to make sure panel doors are sealing properly by observing surface wear on the seals. Larger doors with few latches are particularly problematic as flexing in the door may prevent a uniform seal. And finally, seals ought to be inspected for pinching, tears and proper adhesion to original mating surfaces.
Assume all conduits contain moisture
Another best practice for Dry Cabinets For PCB Storage of electronics assumes that even in the event the conduit penetrations are perfectly sealed, the conduits continue to be going to contain moisture. Underground conduit often is left unsealed during construction (allowing moisture accumulation), and conduit runs can potentially have multiple points where moisture can enter. Conduit with Desiccant Dry Cabinets can transfer water vapor right into a sealed enclosure. Typically, when electronics are energized, heat is generated and also the air in the enclosure can hold even more moisture than ambient conditions, meaning water vapor is less of a problem. The issue happens when the enclosure temperature drops (because of the equipment being de-energized, cooler nighttime temperatures, cooler climatic conditions, etc.) and also the temperature inside xakleh enclosure drops underneath the dew point, leading to condensation.
Expanding polyurethane foam sealant (Fig. 4) provides an excellent way of sealing around conduit cabling: It’s been found to get better than silicone, primarily because caulking guns used in combination with silicone are hard to insert far enough into the conduit to achieve a powerful seal. An expanding foam nozzle attachment can be inserted further in to the conduit to create a highly effective seal around the cabling.