It really is the pits- Zinsco Panels
There are documented issues with Federal Pacific Panel (FPE) and the associated issues with their breakers and how the the Stab-Lok breaker attaches to the buss. The other infamous panel is the Zinsco (which I have written on before).
(Zinsco split bus mains)
I see a few Zinsco Panels each year, about two to three times as many as FPE’s. Yet I physically see more issues with the Zinsco panels even though I see fewer of them overall than the other major panel manufacturers such as Cutler Hammer or Square D of the same age.
Here is are a couple of examples that I see with the Zinsco Panel. Pitting and arcing damage to the bus bars, most likely a poor connection and/or corrosion on the bus. This condition seems to be more prevalent on panels with the aluminum bus bar
There are indications and some reports that the plating and/or quality of the aluminum used on the bus bar lacked good quality control which lead to issues on these bus systems. Add to this the bus design where moving the breakers up and down could wear the plating on the bus.
( Zinsco Breakers )
Another observation I see quite often is the breakers shifting on the bus bar. Loose connection on any electrical component is not good. A loose connection results in higher resistance which equals increased heat at the connection point. There is speculation that the clip design on the breaker may have something to do with this.
( Breakers shifting on bus )
Melting of a bus from poor connections can happen with any panel but my anecdotal observation is that it happens in a greater frequency with these panels because of the bus design and is compounded on those Zinsco panels with the aluminum bus components. Remember older panels of any make may be close to obsolescence for several reasons.
This is why a thorough evaluation should be performed on any of these panels whether there is any obvious signs or not.
Above is another reason to look because some of the issues of these breakers.
Washington State Standards of Practice requires Home Inspectors to report on electrical panel that are known to be problematic.
Washington State Administrative Code - WAC 308-408C-110 Electrical system.
(h) Report- on any circuit breaker panel or subpanel known within the home inspection profession to have safety concerns
Here is a link to one insurance company document- “Risk Alert”
Electrical panels and their associated overcurrent protection are at the heart of the electrical system and the main safety components. Though the level of risk will vary from home to home anyone with these panels should consider replacing these panels.
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