09 Apr 2014

Rust on steel service panel components is by far the most common observation, occurring in 110 (10%) of the installations examined by an electrician in Santa Monica.

Rust on screw connectors on circuit breakers, and less often on fuse terminals, was also common, occurring in 97 cases, slightly less than 10% of the systems examined. In some cases corrosion was so severe that not only was the connection questionable, but the connector screws themselves were so corroded that the electrician had to cut the wire when preparing to install new breakers. When severe rust is present we report that the operation of the circuit breakers might be suspect.

Corrosion on neutral and grounding bus bars and connector screws was found in 42 cases. However field data indicates that bus-bar connector corrosion so severe as to offer visual suggestion that the connection is highly questionable is rare. Evidence of overheating (possibly related to corrosion) was seen in only two of these cases, detected as discolored copper wires at the connector.

Corrosion at the connection of service entrance cable to main breakers or fuse connectors was found in 46 cases. However this connection gives cause for greater concern, as it is not uncommon to see severe corrosion at this location when water is present. We have observed evidence of overheating such as burned insulation and discolored wire and in some instances partially melted aluminum wire at such connectors.

The most common sources of water and moisture entry were: through service entrance conductor cables which were old and damaged, or which were improperly sealed at meter boxes or building sidewalls; from condensation from high interior moisture levels; and from other building leaks or surface water which passed down building walls where panel enclosures were mounted.

Water, often in large volumes from wind-driven rain, followed the entrance cable into the building on three paths:

  1. Frayed electrical service entry cable and bad seal at meter box top when the SEC is located above and enters the electric meter box top, when mounted outside (exposed to weather). Water entered the meter enclosure and traveled down the interior of the plastic-covered electrical service entrance cable into the building, often entering the service entry cable where that cable exited at the meter base.
  2. Inadequately sealed electrical service entry cable connector: While frayed fabric-type SEC covering lets wind-blown rain enter the cable, meter box, and electrical panel, plastic-covered SEC wires form a virtual “water pipe into the electric panel,” conducting water from the electric meter box into the electrical panel.  This occurs when there is a leak into the electric meter box (frayed SEC cable or bad seal at top of the box where the cable enters), and where the electrical panel is mounted in the building at a level lower than that of the meter box.
  3. Inadequately sealed opening where the cable passed through the building wall. A “drip loop” is not generally used at this location. Water followed the outside surface of the cable into the building panel. Capillary action may be a factor.

                For more information on how to avoid rust or corrosion in your electrical panel, call our professional electrician in Santa MonicaUnited Plumbing Heating Air & Electric.