Moisture Control Cabinets – Fresh Light On A Relevant Idea..

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 short article focuses on a number of these best practices.

Assume your enclosure will leak. Unless the application 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 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 will 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 employed for code compliance, enclosure penetrations should be made below energized parts, if at all possible.

When it comes to cable penetrations (versus conduit penetrations), directing water out of the electrical enclosure or housing by using drip loops (Fig. 3) is an additional best practice. The next task is to heat-shrink the connector fittings and alternate wrappings of electrical tape and butyl self-adhesive rubber tape to safeguard against moisture intrusion to the connector.

Maintaining door seals is essential. 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 from the door may prevent a uniform seal. Lastly, seals ought to be inspected for pinching, tears and proper adhesion to original mating surfaces.

Assume all conduits contain moisture

The following best practice for Dry Cabinets For PCB Storage of electronics assumes that even when the conduit penetrations are perfectly sealed, the conduits remain 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 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 a smaller problem. The issue occurs when the enclosure temperature drops (due to the equipment being de-energized, cooler nighttime temperatures, cooler climate conditions, etc.) and the temperature inside xakleh enclosure drops beneath the dew point, resulting in condensation.

Expanding polyurethane foam sealant (Fig. 4) gives an excellent way of sealing around conduit cabling: It’s been found to be better than silicone, primarily because caulking guns used with silicone take time and effort to insert far enough into the conduit to achieve an effective seal. An expanding foam nozzle attachment can be inserted further into the conduit to generate a highly effective seal across the cabling.