Challenger Electric Electrical Panel - bus overheat field report (C) InspectApedia & Lee Challenger Electrical Panels
Field Reports of overheating Challenger Electrical Panel bus & breaker components

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Challenger Electric: electrical panel bus overheats, circuit breaker failures, field reports.

This article includes photographs of overheated Challenger Electric electrical panel components and cites a historical connection between Challenger Electric Company and Federal Pacific Electric. However the specific panel bus and breaker designs are different among those brands.

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Challenger Electrical Panel Bus Overheating Field Failure Report

Overheated main bus insulation & connectors in a Challenger Electrical Panel (C) InspectApedia & Timothy Hemm- Timothy Hemm to InspectApedia December 2014

This is the third Challenger panel I have discovered with this damage. Is there a design flaw or could it be attributed to poor installation workmanship?

I asked Douglas Hanson about this, (if there is any repair) & he said the manufacturers are adamant, when the insulation material is damaged there is no repair.

Tim Hemm

Timothy Hemm, CREIA MCI, ASHI, ICC Certified Inspector, is a professional home inspector in Redlands, California and is a contributor to Mr. Hemm can be contacted at (951)543-3501, or , Website:

Photo at left provided courtesy of Timothy Hemm.

[Click to enlarge any image]



Nice going Timothy. You spotted trouble that in my OPINION most fellows skip.

Challenger Electric Electrical Panel - bus overheat field report (C) InspectApedia & Lee

I agree completely with Doug Hansen and with the panel manufacturers that an electrical panel in which you find evidence of bus overheating and damaged insulating material it is reasonable to conclude that the panel is not safe, not repairable, and should be replaced. In some cases it may be possible to retain the enclosure and install a replacement bus assembly.

Challenger Electric Electrical Panel - bus overheat field report (C) InspectApedia & Lee

See FPE REPLACEMENT PANEL for a discussion of use of the Eaton - Cutler Hammer replacement bus assembly that may be suitable in some applications.

Challenger Electric Electrical Panel - bus overheat field report (C) InspectApedia & Lee

However I emphasize that we do not have the same large body of failure data for Challenger Electric products as we do for FPE Stab-Lok and some other products.

The Challenger Electric Panel photos provided just above and the Challenger circuit breaker photos below were provided by a reader, Lee, who also found evidence of overheating: discolored bus bars (photos above) in Challenger Electric panels and breakers.

Challenger Electric circuit breaker involved in overheated panel (C) InspectApedia Lee

I've looked into this very sort of panel damage with some FPE panels , under tutelage of the real expert, Dr. Aronstein. We saw that the bus insulation was sorely compromised by overheating - in some cases when we disassembled the panel the damage behind the components that you could see in-situ was far more severe. We even found blobs of melted plastic on the bottom of the panel.

While I suspect that some of these failures are probably caused by overheating at the breaker to bus connection, which might in turn argue that a breaker is not tripping when it should, we can't conclude the cause for sure from just your photos. They're great but not comprehensive, nor do we know building history, wiring snafus, etc. In sum to be "professional" we need to a bit reticent about asserting cause when we don't have more data and more forensic analysis.

Bottom line, whether you're seeing a product defect or overheating caused by an installation error, it is reasonable to conclude that the panels you're seeing with this symptom are unsafe and should be replaced.

Interestingly, the failure pattern and location is quite similar to bus overheating damage seen in FPE panels. Doug and I may not see eye to eye on how to discuss that overheat damage, as I think it's caused by a root problem of breakers that don't trip while I think Doug may consider it a separate defect. He's been looking at FPE faults besides the fundamental one (breakers that don't trip in response to overcurrent) for some time.

At we report that Challenger was in fact in the ownership path during the history of the demise of FPE. One might reasonably suspect that some engineers, designers, production line employees, and even equipment may have moved from FPE to Challenger at that time.

Thanks again for the photos, I'll be sure to add these to our discussion of Challenger field reports and of course blame you for their origin.

Any chance you can get a hold of one of these panels? If so, clip the wires - don't disturb anything on the bus assembly, and I'll ask that you send it either to me or directly to Dr. Aronstein if he's willing to do some more through forensic work on the panel.

Field Report: Challenger Panel Accepting Eaton CH Type BR Breakers: Overheating

Challenger electrical panel bus overheat (C) InspectAPedia CS

About 2 years ago I sent you an email regarding my Challenger panel that accepts Eaton Cutler Hammer type BR circuit breakers, and wanted to let you know what happened recently.

I was inspecting the panel and found that the piece of bus that feeds the main bus that comes from the main breakers was very discolored.

[Click to enlarge any image]

So I found out that the main breaker is a Zinsco style (model QFP2200) that sits on a mini Zinsco style bus bar.

After my electrician pulled out the old panel I pulled out the breaker and found that the Zinsco bus was fine, and it seemed to me that the main problem with this panel design was the underrated bus connections.

Challenger electrical panel bus overheat (C) InspectAPedia CS

It was a 200a panel. I just had the panel replaced with a Murray.

I wanted to share with you some pictures.. (attached) thank you for your time.. hopefully this will be helpful to people on your website. - Cameron 11/19/2014


The discoloration in your photos most likely indicates overheating that could be for any of several reasons. An effect can be corrosion, poor bus connections, and an increased risk that a breaker may not respond properly to an over-current. I'm relieved that you replaced the panel.

Reader follow-up:

I work at home depot in the electrical department and am always referring people to your website. There are so many people in my area with Zinsco and FPE Panels. I also am amazed at how many people think it is ok to use any brand breaker in any panel, I think that might be another helpful article (if you haven't already done it) on how using the wrong brand although it still fits voids the manufacturer and UL listing and warranty. - C.S. 19 Nov 2014

More Challenger Electrical Panel Field Reports

Overheating burns in a Challenger electrical panel (C) InspectApedia SM

Photographs of this ca 1980's Challenger electrical panel were provided by a licensed electrician in California who recommended electrical panel replacement as the overheated panel and its circuit breakers were considered unsafe. The electrician noted:

Notice the burning and discoloration on the buss bar on the line and load side of the meter socket . It also carries on into the distribution side as well on the very same phase.... Not only did the client have over-heating & burning inside his panel, (which may have resulted/caused from the bad utility connection) ,but he also had poor utility connection as well. - private email DF / anon 2016/01/25

We agreed, stating

... electrical panel bus discoloration, if not obvious corrosion, is a reliable indication of over heating. That is an abnormal and unsafe condition as its likely to mean overcurrent have been present without the breakers tripping. I suspect faulty circuit breakers in that case.

Even before condemning the panel based on brand and history data, the overheating is a serious red flag and argues for replacement - something one would reportage advise. Adding the brand adds emphasis. I've also found signs of overheating on local grounds when the utility company's neutral connection is poor or lost. (LOST NEUTRAL SHOCKS HOMEOWNER ). However even a loss of power on the utility side of the meter and panel would not (in any way I can see) explain overheating on one leg of the panel main bus nor in the panel itself.

History of Challenger Electrical Panels and Challenger-FPE-Stab-Lok Design circuit breaker products

Excerpting comments posted by Jraef, a moderator in Mike Holt's electrical forum on 11/18/2015, original source: with [Editor's annotations] - Ed.

Challenger [Electric] became part of Eaton [Cutler Hammer] years ago, but had bought the rights to the [FPE] Stab-Lok breaker when FPE went bust. Eaton however wanted no part of that legacy, so they had Challenger sell off that product line before the takeover. They sold it to a company called Providence, [sic, actually "Provident Electric" - Ed.] who later [in 1988] changed their name to American Circuit Breaker Co. (ACBC). They now own the rights to sell that breaker as a "Stab-Lok" replacement breaker.

But the old FPE also had an independent Canadian division, and THAT division had the rights to make and sell the Stab-Lok breakers in Canada and as they later claimed, the US as well. The name of that company changed to Federal Pioneer, then later just Pioneer. Pioneer was then later bought by Schneider, who of course owns Sq. D too, but Schneider wanted no part of marketing the Stab-Lok breakers in the US. In a huge fight over this, ACBC settled on giving up their production facility in South Carolina that was making the breakers, in deference to Pioneer making them for them in Canada at a guaranteed price. At the same time Schneider gave up the rights to sell and use the name Stab-Lok in the US and ACBC cannot sell in Canada. The Canadian version is made as grey, the US version is still black. The Canadian grey versions still make it here on the "grey market" (ironically) and are exactly the same beside the color of the plastic. If you see Stab-Lok breakers that still say Challenger on them, they are old stock, as in pre-1988. Challenger, as a brand name now owned by Eaton, has no official connection to that product any longer.

When Schneider forced ACBC to stop making the Stab-Lok breakers, Connecticut Electric (CE) supposedly bought the old ACBC factory in South Carolina including the molds and machinery used to make the old Stab-Lok breakers (they moved it I think). But they do not have the rights to the name "Stab-Lok", so you will not see it on their version. In addition, they did not get the rights to the UL listings for them in FPE load centers. So the only thing CE could do is get their versions "Classified" for use in FPE load centers, and because UL had a problem with FPE's listings even when they were FPE, CE got listing under ETL (which some people view as "easier" to get than UL).

Also see FPE STAB-LOK HISTORY where we include details of the history of FPE, Federal Pacific Electric Company, American Circuit Breaker Company [ACBC], Oregan Breakers, INc., Provident Industries, Federal Electric Products (Canada), Pioneer Electric (Canada), Schneider Electric Canada and others.



Continue reading at FPE FIRES: FAILURE REPORTS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



Or see FEDERAL PIONEER PANEL SAFETY where Challenger and later ACBC American Circuit Breaker Company "FPE Stab-Lok" breakers are discussed.

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