Outdoors, or in wet indoor environments like wash-down areas, Dry Storage Cabinets of electronic systems start with the design of the enclosures and penetrations, and end with the design and configuration of the components. This post targets a number of these best practices.
Assume your enclosure will leak. Unless the applying calls for a vented enclosure (e.g., for heat dissipation, battery off-gassing), a sealed enclosure represents the first line of defense against moisture. Unfortunately, even the best NEMA 4 electrical enclosure works well until poor installation practices or out-year modifications create poorly sealed penetrations (Fig. 1).
It’s advisable to think that penetrations into any enclosure will leak (as shown by Fig. 2). Based on this assumption, top-mounted conduit penetrations where moisture can collect on horizontal surfaces ought to be avoided. Even if Myers hubs or sealing locknuts are used for code compliance, enclosure penetrations should be made below energized parts, whenever possible.
When it comes to cable penetrations (versus conduit penetrations), directing water out of the electrical enclosure or housing with 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 guard against moisture intrusion in to the connector.
Maintaining door seals is incredibly important. Door seals needs to be inspected to ensure panel doors are sealing properly by observing surface wear on the seals. Larger doors with few latches are particularly problematic as flexing of 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 following best practice for Dry Storage Cabinets For Optics of electronics assumes that even when the conduit penetrations are perfectly sealed, the conduits continue to be likely 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 in to a sealed enclosure. Typically, when electronics are energized, heat is generated and the air within the enclosure can hold even more moisture than ambient conditions, meaning water vapor is a smaller problem. The issue occurs when the enclosure temperature drops (because of the equipment being de-energized, cooler nighttime temperatures, cooler weather conditions, etc.) and also the temperature inside xakleh enclosure drops underneath the dew point, leading to condensation.
Expanding polyurethane foam sealant (Fig. 4) offers 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 take time and effort to insert far enough into the conduit to accomplish a powerful seal. A growing foam nozzle attachment can be inserted further to the conduit to create a powerful seal around the cabling.