Outdoors, or in wet indoor environments like wash-down areas, Dry Storage Cabinets of electronic systems start 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 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 very 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 assume that penetrations into any enclosure are going to leak (as shown by Fig. 2). Based upon this assumption, top-mounted conduit penetrations where moisture can collect on horizontal surfaces should be avoided. Even if Myers hubs or sealing locknuts are being used for code compliance, enclosure penetrations needs to be made below energized parts, if possible.
In terms of cable penetrations (versus conduit penetrations), directing water out of the electrical enclosure or housing by using drip loops (Fig. 3) is another 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 guard against moisture intrusion into the connector.
Maintaining door seals is essential. Door seals should 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 from the door may prevent a uniform seal. And lastly, seals needs to be inspected for pinching, tears and proper adhesion to original mating surfaces.
Assume all conduits contain moisture
Another best practice for Dry Storage Cabinets For Optics 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 Moisture Control Cabinets can transfer water vapor 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 a smaller problem. The issue takes place when the enclosure temperature drops (because of the equipment being de-energized, cooler nighttime temperatures, cooler climate conditions, etc.) as well as the temperature inside xakleh enclosure drops beneath the dew point, causing condensation.
Expanding polyurethane foam sealant (Fig. 4) gives an excellent way of sealing around conduit cabling: It’s been found to get preferable over silicone, primarily because caulking guns used with silicone are difficult to insert far enough into the conduit to achieve a powerful seal. A growing foam nozzle attachment can be inserted further into the conduit to produce a powerful seal round the cabling.