UBI FPE circuit breaker smoking under test at 400% of rated current (C) & J Aronstein 2017UBI Replacements for FPE Stab-Lok®
UBI-FP Circuit Breaker Failure-Test Results

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UBI-brand FPE Circuit Breaker Replacement test results:

Current results of overcurrent tests performed on UBI circuit breakers sold as replacements for FPE Stab-Lok circuit breakers: as of April 2017, testing of 420 UBI circuit breakers show overall a high failure rate of about 42% - higher than FPE circuit breakers, and significantly-higher than the performance of most other brands and designs of circuit breakers.

In addtion, two-pole UBI breakers frequently jam after which they will not trip at any level of overcurrent.

This article series gives expert advice about replacing FPE Stab-Lok® circuit breakers - Federal Pacific Electric Stab-Lok® breakers and discusses how to repair FPE StabLok Panels and circuit breakers for actual improvements in electrical safety.

Replacement FPE Stab-Lok® circuit breakers are unlikely to reduce the failure risk of this equipment. We recommend that residential FPE Stab-Lok® electrical panels be replaced entirely or the entire panel bus assembly be replaced, regardless of FPE model number or FPE year of manufacture. We do not sell circuit breakers nor any other products. 

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

UBI Replacement Circuit Breaker Independent Test Results - 2017 Update

UBI brand replacement circuit breaker (C) EliUBI replacement circuit breakers like the equipment shown at the top of this page are sold as replacement units for FPE Stab-Lok or Federal Pacific Electric or Federal Electric or Federal Pioneer circuit breakers, and for other electrical panel brands including for Zinsco circuit breakers.

The photo of gray 15, 20 and 50A circuit breakers shown just above/left illustrates UBI-brand replacement circuit breakers, provided by reader E.K. (2014) who included the image in an FPE UBI breaker field failure report described at FPE FAILURE FIELD REPORTS.

Page top photo of smoking UBI - FPE circuit breaker: The FPE-replacement UBI circuit breaker shown at the top of this page smokes without tripping off when subjected to 60A or 400% of rated current.

Smoke (red arrows) is coming out of the toggle slot at the top of the breaker and out of the arc chute (lower right). The orange arrow points to a burn spot near the breaker bottom where internal parts are overheating.

[Click to enlarge any image]

The test conditions that led to this smoking breaker that did not trip in response to an overcurrent are explained by Dr. Jess Aronstein:

One of the 15-amp 2-pole breakers [among a group of UBI breakers undergoing independent testing] went to 200% of rated current without tripping. Typically, when a circuit breaker does not trip at 200% it is not a calibration error, but is most likely due to jamming of the mechanism. It happens most often on the 2-pole breakers.

I ran the jammed 15-amp breaker up to 60 amps, 400% of rated current. It still did not trip. The photo below was taken just before I shut it down. - J.A. by private email to editor 2017/03/04

Results of Independent UBI-FPE Circuit Breaker Tests

A reader E.K. corresponded with us beginning in 2014 that in 2004 his condominium association replaced all of the old original FPE circuit breakers in the condominium complex with UBI replacement breakers. The reader explained that he discovered that the new replacement UBI circuit breakers were faulty.

The reader quoted below, a resident of Northgate Gardens, a large condominium complex in Waltham MA, subsequently provided a collection of UBI circuit breakers to Dr. Jess Aronstein for independent testing. Results are reported below.

The same person who sent these UBI circuit breakers to Aronstein for testing is an electrical engineer (EE) who had one circuit breaker passing about 200% of rated current without tripping. He had his panel changed and the condo board is considering making it a mandatory change in all other units. (They "upgraded" from the original FPE breakers some years ago.)

In a letter to the condominium board the reader's comments included this remark:

In my other condo we also had the same type of electrical panels; back in 2003 we had a fire inside a wall of one of the units which caused extensive damage, we were fortunate that no one was injured. - Anon [by private email]
[Editor's note: the 2003 fire referred to by the reader's comment took place at a different facility, not at Northgate Gardens in Waltham. However that distinction does not preclude the occurrence a fire or other loss involving an FPE electrical panel wherever that equipment remains installed.]

Below we provide two tables of independent test results for UBI-Brand replacement circuit breakers for FPE panels. The first table is a summary of test results to date while the second table provides more details of some of the tests.

Table I Summary of FPE UBI-Brand Replacement Circuit Breaker Failure Test Results

Summary: All Nortgate Condo UBI®-F Stab-Lok® (FPE Replacement) Circuit Breakers Tested

  Number Tested n=265 Failure Percent
Total # UBI Breakers Tested from Northgate 420  
   Breakers Failing to Meet UL 135% Trip Requirement 177 42%
   Critical Safety Failures (no trip @ 200%) Subset of the 135% no-trip total 14* 3%
         * Subset of the 135% no-trip total
Breakers by Type Included in the Summary Above - Single-Pole vs. 2-Pole Number Tested n=312 Failure Percent
Single Pole UBI - FPE Breaker Tests    
Total # Single Pole UBI Breakers Tested 3121  
   Breakers Failing to Meet UL 135% Trip Requirement 122 39%
   Critical Safety Failures (no trip @ 200%) Subset of the 135% no-trip total 0 0 %
Double Pole UBI - FPE Breaker Tests    
Total # Double Pole UBI Breakers Tested 1081  
   Breakers Failing to Meet UL 135% Trip Requirement 55 51%
   Critical Safety Failures (no trip @ 200%) Subset of the 135% no-trip total 14 13%


Some FPE-UBI Breaker Test Details

Table II - Example Subset of Table I Above: FPE UBI-Brand Replacement Circuit Breaker Failure Detailed Test Results1

Breaker ID & Ampacity Quantity Breaker Type:
Test Result Comments
UBI - FPE Replacement Circuit Breaker Tests: 2016-2017
UBI 15-Amp 20 Single Pole

9 failures @ 135% - 45% failure rate

Failure = failed to trip at 135% of rated current - the UL Standard requirement
UBI 15-Amp 3 Double Pole

2 failures @ 135% - 67% failure rate

Small sample size.
UBI 50-Amp 6 Double Pole

3 failures @ 135% - 50% failure rate

2 failures @ 200% - 33% failure rate

The 2 that failed to trip at 200% of rated current jammed, making them unlikely to trip at any current level.
UBI - FPE Replacement Circuit Breaker Tests: 2014
UBI 15-Amp 3 Single Pole 2 failures @ 135% - 67% failure rate  
UBI 20-Amp 2 Single Pole 2 failures @ 135% - 100% failure rate  
UBI 50-Amp 1 Double Pole 1 failure @ 135% - 100% failure rate  

Notes to the table:

FPE-UBI Breaker Test data as of 2 January 2017

UBI FPE Replacement Breaker Test Comments from Dr. Aronstein:

Overall, half of the UBI breakers so far tested from Northgate Gardens failed to meet the industry (and therefore the NEC) safety standard requirement. The safety exposure due to these failures ranges from mild to severe (the 50-amp jammed breakers).

The test procedure that I use encompasses the UL 100% (should not trip), 135% (must trip within one hour), and the 200% (must trip) requirements. Breakers that fail to trip properly are on the test stand for more than two hours. A failing double pole breaker can take more than 6 hours to test. Based on the UBI circuit breaker failure rate experienced to date, I expect it to take about three weeks to complete testing of the first batch that you have sent.

The more breakers that are tested, the more certain the conclusion will be -- from a statistical standpoint -- and the more likely it will be that corrective action will be taken by other homeowners and by responsible government agencies.

So, all readers are encouraged to collect and send samples of FPE replacement-type circuit breakers.

Older FPE-UBI Breaker Test Data: 3 December 2014:

Included in the lower portion of the table above are the December 2014 results of the tests on the UBI "Stab-Lok" (FPE replacement) circuit breakers that you sent. The breakers were tested at 135%, which is the required UL "must trip" level. Those that failed to trip at 135% (sustained for one hour minimum) were subjected to higher current until they tripped or reached 200% of rated current.

Five of the seven UBI breakers that the reader sent failed to trip as required at 135% of rated current. The sample size is small, but it may properly reflect the state of UBI's quality control at the time your breakers were purchased.

Overall, [J.A. had as of 12/14 ] tested 23 UBI Stab-Lok type breakers, with 8 failures. I have also tested 3 UBI Zinsco replacement type breakers, and all 3 failed to trip as required at 135%. [See ZINSCO CIRCUIT BREAKER TEST REPORT] That totals 11 failures out of 26 UBI breakers tested [in 2014].

  • Jesse Aronstein 1, (Life Senior Member, IEEE), & David W. Carrier 2 MOLDED CASE CIRCUIT BREAKERS - SOME HOLES IN THE ELECTRICAL SAFETY NET [PDF] Received December 4, 2017, accepted January 24, 2018, date of publication February 7, 2018, date of current version March 15, 2018. Digital Object Identifier 10.1109/ACCESS.2018.2803298
    1 Consulting Engineer, Schenectady, NY 12309, USA, 2 SUNY Dutchess Community College, Poughkeepsie, NY 12601, USA, Corresponding author: Jesse Aronstein (

    This paper is also available at no charge at the IEEE Explore website. It can be accessed for online reading at:
    and can be downloaded directly from IEEE at
  • Jesse Aronstein, Ph.D., P.E., 2 January 2017, private email to E.K. and to D Friedman.
  • Jesse Aronstein, Ph.D., P.E., 3 Dec 2014, private email to E.K., B.G. and to D Friedman.
  • EK to J.A. & to the Editor, 2017/01/02: Thank you Dr. Aronstein,

    This gloomy initial result should prove to anyone who still believe it is a mistake to replace the FPE panels on the complex that all panels must be replaced.
    I will do my very best to convince other electricians who work on the complex to donate the old breakers to this important study.

    So, stay tuned, many more breakers will be shipped to you for testing. It will be helpful that when the final report will be published the names of the electricians who agreed to donate their old breakers will be mentioned.
  • EK to J.A. & to the editor: 2015/08/13

    Thank you Dr. Aronstein, the failure rate is alarming (above 70%). These breakers have a sticker date of 2004. Did the breakers that failed the 135% test did eventually trip at higher current below 200% of the rated current?
    -Anon to J Aronstein & D Friedman, 12/3/2014, updated 13 August 2015
  • Kelly, Timothy P., "[FPE] ELECTRICAL PANEL [REPLACEMENT] CLARIFICATION" [PDF], letter, Kelly to Northgate Board of Trustees / Condo Association, Jacqueline Road, Waltham MA 02452, 21 November 2016.

    This letter recommends replacement of the FPE Federal Pacific Electrical panels and notes that the Northgate Garden's Board of Trustees had at that time decided to mandate that the panels be replaced.
  • EK to Editor, by private email 2017/03/14: All electricians who helped in this study by donating the old breakers to be mentioned and thanked. Here are more electricians to thank:
    • Chad Garvey, Burlington, MA. 781 983-5630, Email:
    • David Palmieri, Randolph, MA. 781 961-7400, Palmieri Electric, Email:
  • FPE FAILURE FIELD REPORTS - reports of actual Federal Pacific and Federal Pionieer and UBI panel and circuit breaker failures
  • William Tinker, licensed Master Electrician, Gilbertville MA, contributor of the UBI FPE circuit breakers whose test reports are described as of 2 January 2017.
    Contact: William Tinker, Master Electrician, 233 Upper Church Street, Gilbertville MA 01031 USA, Tel: 1-774-230-3837 Email
  • ZINSCO CIRCUIT BREAKER TEST REPORT - similar testing on replacement circuit breakers sold for Zinsco electrical panels

UBI (or other brand) Replacement FPE or FP Stab-Lok Circuit Breakers for Testing

Updated, 2017/04/18: The sample size of Northgate UBI circuit breakers is considered sufficient to prove the defect level.

Three thousand FPE type breakers tested to date (2018): the statistical certainty of conclusions drawn from the data is very high.

These breakers have a significantly-high rate of failure to perform safely. Details are at CIRCUIT BREAKER FAILURE RATES and also at FPE INVESTIGATION CPSC

Homeowners and renovators who encounter these panels should replace the entire panel and circuit breaker set with new equipment. Panel replacement, can involve significant expense, typically $800 to $1800 depending on service size and other factors.

FPE - UBI Replacement Circuit Breaker Discussion [with a vendor of replacement breakers]

For space and clarity, this discussion is now located at UBI CIRCUIT BREAKER VENDOR COMMENTS On FPE Stab-Lok replacement breakers, posted by a manufacturer sales representative as comments to FPE Stab-Lok® : FIRES WAITING TO HAPPEN.

U.L. 489 Circuit Breaker Test Standard

Below is a description of the UL (and probably ETL) follow-up service for breakers listed under UL489. Note that the only testing required is at the factory, "observed" by the UL inspector.

Certification tests to the UL 489 Standard are witnessed by UL engineering representatives. At the successful completion of the test program, UL permits circuit breakers to bear a UL Listing mark combined with the product identity of “CIRCUIT BREAKER” or “CIRCUIT BREAKER FRAME.”

These circuit breakers are then required to undergo subsequent follow-up testing on a regular basis: quarterly, semiannually or biannually depending on the circuit breaker size and quantities produced. All follow-up tests are witnessed by UL field representatives.

Watch out: In our opinion there is a big hole in the electrical safety net. Nobody is sampling replacement circuit breakers from the market chain to check their quality level, and there is no test data available to the public to serve as guidance in selecting a brand of breaker.


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Continue reading at FPE REPLACEMENT BREAKERS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see CIRCUIT BREAKER FAILURE RATES - independent test results for several widely-used brands of circuit breakers


Or see FPE FAILURE FIELD REPORTS - over 270 field reports concerning FPE circuit breaker failures




Or see ZINSCO CIRCUIT BREAKER TEST REPORT - similar testing on UBI replacement circuit breakers sold for Zinsco electrical panels

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Publisher - Daniel Friedman