Danger - rust in electrical panel box components.
The percentage of the time would be unknown, but I often see rust in panel box components.
There is debate surrounding how much is too much.
To me there cannot be much debate or room for error.
Corrosion is corrosion; damage is damage; electrical components are electrical components - and you just can't be too careful!
Once after identifying a severely rusty panel box, with the components and connections inside similarly very rusty, an electrician called by the homeowner said "some rust is normal." Later, that same house had an overheated condition that caused scorching and necessary replacement of the entire box and components. Normal, you say?
How much rust is "some rust..."?! Corrosion begins for a reason. Once started what would slow it? According to IEEE studies, 66% of moisture in panel boxes comes from service entrance cable defects, 17% from indoor condensation and 17% from surface/roof runoff or leakage.
The IEEE (Institute of Electrical and Electronics Engineers) is the world's largest collection of electrical experts and has an annual convention. Each year rusting panel boxes or components inside seem to be on the discussion/education agenda. And with good reason.
Here is what they say about home inspectors: Visual examination of the electrical service panel is an important element of the procedure followed by professional home inspectors, whose observations are most often made at the time of sale of a used residence. The inspectors' observations can provide a data base on field performance of residential electrical system components that may be valuable toward the development of improvements in both the components and their associated qualification standards.
Professional home inspectors offer a unique perspective of field failures: in performing a comprehensive survey of a building's systems and components, an inspector may discover common external or interactive causes of damage or deterioration. Home inspectors regularly observe field deterioration in progress before hazards or malfunctions are so obvious as to come to the attention of the occupants.
The reported observations in electric panels include corroded, burned, and damaged connections and corroded and malfunctioning circuit breakers. Causative factors noted in the service environment include presence of moisture, damage from over current, and poor installation practices. Suggested improvements, including the need for greater resistance to corrosion and other field and environmental conditions, are discussed.
That is pretty descriptive of what home inspectors do! We possess thousands and thousands of eyes that are in addition to county inspectors, and other electrical investigators.
My recommendation: electric panel box evaluation is an important part of a home inspection. Home inspectors are cautioned NOT to go inside a panel box that shows rusting on the cover or breakers. It is important that the panel box be accessible to the home inspector and it's important that it be investigated when possible. There is a lot that can go wrong!
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560