Safety and corrosion in electrical panels
In service inspection of electrical panels is a requirement of numerous electrical standards including AS/NZS 3000 Electrical Installations and AS/NZS 3019 Periodic Verification. Part of the inspection process should include an assessment of any rust or corrosion present within the panel. Rust and corrosion can occur on both steel, copper and silver components used within the electrical panel and if left unchecked can give rise to serious problems.
A study undertaken in the USA of some 1,052 electrical panels found 12 percent of them had severe corrosion issues, to the level that the corrosion needed immediate remediation under the reporting rules present. Light corrosion was present in some 40 percent of all panels inspected.
Cause and effect of corrosion
Causes of corrosion in electrical panels can include the presence of moisture from the atmosphere, poor installation practices allowing water to enter the panel or the presence of corrosive gases such as hydrogen sulphide.
The effect of corrosion in electrical panels includes: • General unsafe operating conditions
resulting in earth leakage; • Electrical malfunction (intermittent)
through to complete electrical circuit failure; • Overheating; • Fire.
From a safety perspective any of the above is of concern, ranging from minor through to significant issues which can ultimately affect the well-being of both people and equipment/ buildings.
Light corrosion such as surface rust on the panel enclosure will generally not result in electrical failure but is an indication that all is not well inside the electrical panel and that remedial action should be implemented. Severe corrosion will manifest itself with rust evident on any steel components used inside the panel such as steel screws used in terminal connectors. Corrosion on service entrance wiring, fuse blocks or circuit breakers and busbars/connectors is a sure sign of major issues ahead.
Corrosion due to the environment
a. Moisture and water ingress. Water and moisture inside an electrical panel are the major causes of corrosion seen. This can occur through: • Improperly sealed service entry conduits or the seal has deteriorated and perished over time; • Condensation inside the electrical panel due to changes in temperature or humidity levels; • Surface water leaking in to the electrical panel, generally from behind the panel, due to poor installation practices or the failure of cable glands. b. Corrosive gases Gases such as hydrogen sulphide, chlorine, hydrochloric acid and sulphuric acid will cause corrosion of the electrical panel. The higher the level of corrosive gases present the more rapid the rate of corrosion with some panels going out of service after as little as three months. These gases are present in some industrial operations such as paper mills and waste water treatment plants but also occur in nature such as in geothermally active areas.
Hazardous and unsafe conditions may be present in electrical panels due to rust and corrosion. As the corrosion resistance of the parts used inside an electrical panel are generally note known it is better to prevent corrosion from occurring through various abatement measures.
Resistance against corrosion can be improved by properly sealing electrical panels against water and moisture ingress, providing dry conditions inside an electrical panel by the use of heaters or a desiccant and protecting against corrosive gases by the use of positive air pressure, air scrubbers or neutralisers.