Outdoors, or in wet indoor environments like wash-down areas, Electronic Dry Cabinets of electronic systems begin with the appearance of the enclosures and penetrations, and end with the design and configuration of the components. This post targets several of these best practices.
Assume your enclosure will leak. Unless the applying requires a vented enclosure (e.g., for heat dissipation, battery off-gassing), a sealed enclosure represents the initial line of defense against moisture. Unfortunately, even the most effective NEMA 4 electrical enclosure works well until poor installation practices or out-year modifications create poorly sealed penetrations (Fig. 1).
It’s better to believe that penetrations into any enclosure are likely to leak (as shown by Fig. 2). According to 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.
In terms of cable penetrations (versus conduit penetrations), directing water from the electrical enclosure or housing through the use of drip loops (Fig. 3) is yet another best practice. The next thing is to heat-shrink the connector fittings and alternate wrappings of electrical tape and butyl self-adhesive rubber tape to safeguard against moisture intrusion into the connector.
Maintaining door seals is essential. Door seals needs to be inspected to make certain 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 needs to be inspected for pinching, tears and proper adhesion to original mating surfaces.
Assume all conduits contain moisture
The next best practice for Dry Cabinets For PCB Storage of electronics assumes that even if the conduit penetrations are perfectly sealed, the conduits remain planning 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 Dehumidifying Dry Cabinets can transfer water vapor into a sealed enclosure. Typically, when electronics are energized, heat is generated as well as the air within the enclosure can hold even more moisture than ambient conditions, meaning water vapor is less of a problem. The problem occurs when the enclosure temperature drops (as a result of equipment being de-energized, cooler nighttime temperatures, cooler climatic conditions, etc.) as well as the temperature inside xakleh enclosure drops below the dew point, causing condensation.
Expanding polyurethane foam sealant (Fig. 4) gives an excellent method of sealing around conduit cabling: It’s been found to be preferable over silicone, primarily because caulking guns used in combination with silicone are difficult to insert far enough into the conduit to achieve a powerful seal. An expanding foam nozzle attachment can be inserted further into the conduit to generate an effective seal around the cabling.