How Submersible Electrical Enclosures Are Tested

Submersible electrical enclosures are tested using leak detection and pressure-based methods to identify ingress points and verify performance under sustained submersion conditions.

·        Leak detection using pressurized air and soap-based solution to locate failure points

·        Pneumatic pressure testing to simulate sustained submersion conditions

·        Vacuum and submersion testing to validate sealing under different pressure environments

·        Verification using ISO 17025 calibrated digital instrumentation for accuracy and traceability

·        Repeated testing to confirm consistent performance and eliminate hidden failure points

Testing does not assume performance based on a rating. It verifies sealing integrity under controlled conditions that simulate real-world environments.

Testing identifies where failure begins, eliminates those weaknesses, and confirms performance under sustained pressure.

Testing That Focuses on Failure Points First

Standard NEMA 6 and NEMA 6P ratings define baseline performance for submersible enclosures. NEMA 6P, specifically, requires that an enclosure withstand submersion to 6 feet of water for a minimum of 24 hours without water ingress. For engineers who work across both rating systems, that aligns with IP68, the IEC equivalent for continuous submersion beyond 1 meter, at manufacturer-specified depth and duration. Standards define baseline performance, but they do not identify where an enclosure is most likely to fail. That is where testing begins.  

Every NEMACO™ submersible enclosure goes through a pre-test designed to identify potential ingress points before full performance testing takes place. Each unit is individually tested, not batch tested, to ensure sealing integrity and performance. The enclosure is first inspected, then connected to a pressure line, fitted with ISO 17025 calibrated digital gauges, and pressurized with air, measured in PSI.  

A soap-based solution is applied across seams, fittings, pipe connections, and cable entry points. Particular attention is given to high-risk areas such as cable penetrations and sealing interfaces, where proper bolt torque and consistent gasket compression are essential to maintaining sealing integrity under pressure. If air escapes, it forms visible bubbles. That is the failure point. This becomes more important as pressure increases with depth, placing greater demand on sealing systems.

If air can escape, that is exactly where water will enter under submersion. This step matters because it identifies weaknesses early, before full performance testing begins.

Pneumatic Performance Testing

Once the enclosure passes leak detection, it moves into full performance testing using pneumatic pressure.

Air is introduced into the enclosure via a compressor and measured with ISO 17025 calibrated digital gauges. Pressure is held at specified thresholds and sustained for a defined duration, not released at peak and logged as a pass. This simulates real-world conditions where pressure is sustained, not momentary, allowing performance to be evaluated under controlled pressure conditions that simulate submersion at varying depths. At greater depths, increased pressure directly impacts sealing performance.

Typical validation includes testing at depths of 15 feet, with extended testing capability up to 135 feet depending on application requirements. For deeper conditions, pressure is simulated rather than relying solely on physical submersion tanks, allowing performance validation at depths beyond practical tank limitations.

This is not a single-pass test. It is repeated to confirm consistency and eliminate variables that can mask failure points, including connection-related leaks, which are among the most common real-world causes of enclosure failure. Each round of testing ensures the enclosure performs reliably under repeated conditions.

Alternative Testing Methods Based on Application

Depending on the application, additional testing methods may be used to evaluate performance under different conditions. These methods allow validation under both positive and negative pressure conditions. They also support UL Listed requirements by verifying enclosure performance under the intended use conditions.

Tests may include:

·        Hose-directed spray testing at 70+ GPM
Used to validate enclosure performance under washdown conditions associated with NEMA 4 and NEMA 4X ratings

·        Vacuum testing using inHg (inches of mercury) measurement
Used to simulate negative pressure conditions where external pressure exceeds internal pressure, validating enclosure performance under both positive and negative pressure differentials

·        Submersion testing in a water tank using pneumatic pressure
A direct simulation of field conditions, used to validate sealing performance under sustained immersion and increased pressure conditions associated with depth

·        Submersion testing using vacuum conditions
Used when validation is required under both positive and negative pressure differentials, providing a more complete sealing integrity profile across varying pressure conditions

Together, these methods provide different ways to evaluate sealing integrity and performance across pressure variation, environmental exposure, and long-term material aging.

Detecting Micro Leaks Before They Become Failures

Not all leaks are obvious. Micro leaks occur at:

·        Multi-pin bulkhead connectors

·        Solid core wiring

·        Multi-stranded wire connections

These areas are particularly susceptible because they introduce multiple potential paths for ingress. Bubble leak testing is especially effective here. Even small leaks become visible, revealing failure points early in the testing process.

Results Are Verified, Recorded, and Traceable

Testing alone is not enough. Verification and accountability are part of the process. NEMACO™ enclosures are designed and tested in accordance with UL 50 and UL 50E, the standards governing enclosures for electrical equipment, covering construction requirements, environmental testing, and routine production inspection. All measurements are taken using ISO 17025 calibrated digital instrumentation to ensure accuracy, repeatability, and traceability. This includes documenting pressure readings, identifying leak locations, and confirming that issues have been resolved.

Only after the enclosure successfully completes all stages of performance testing and verification is it approved for deployment. Each enclosure is then assigned a unique serial number that remains with the unit throughout its lifecycle. The serial number links directly to its testing and verification history. This provides full traceability and confirms that the enclosure passed testing and was validated for deployment.

Why This Process Matters

Submersible environments are unforgiving. They often involve flooding, coastal exposure, and extreme weather events such as hurricanes and tornadoes. Water does not need a large opening. It only needs a path, no matter how small or difficult to detect. That is why submersible enclosure testing cannot rely on a single pass/fail result. It has to identify where failure begins, verify that those points are eliminated, and confirm that the enclosure performs under sustained pressure.

Pressure, time, and environmental exposure do not act independently. Together, they create the conditions where failure actually occurs. This is the difference between enclosures that meet a rating and those that perform reliably in the field, under sustained conditions.

In applications where enclosures are expected to perform under sustained or prolonged submersion, purpose-built submersible designs are essential.

Explore SubPro™ enclosures engineered for these conditions.

Disclaimer: This information is provided to the general public as a courtesy and serves as a general guideline. Readers should consult the most current standards for NEMA ratings, UL listings, the IP rating system, and the National Electrical Code, as these standards may be revised or updated.