Logo: Electrical-Forensics.com Email Icon Phone Call Icon copywrite notice

Circuit Breakers


Most circuit breaker problems are due to loose electrical connections; however, there are some inheritance problems with specific brands of circuit breakers.

When a circuit breaker trips, it releases a cocked spring mechanism that separates the electrical contacts. Circuit breakers have two means of tripping:

(1) An electromagnet that trips almost instantaneously when the current is between nine (9) and 15 times the rated current of the circuit breakers (USA),

and

(2) A temperature sensitive bimetal strip that bends and releases the spring mechanism at a calibrated temperature. Usually, the temperature of the bimetal strip is proportional to the amount of current passing through the circuit breaker. However, the bimetal strip will react and bend to any rise in temperature. The rise in temperature may be due to a loose wire connection, misalignment of the circuit breaker contacts, or the heat from a fire.

Circuit breakers are sized to protect the integrity of the wire insulation; they are not sized to protect human life.

If a circuit breaker is over loaded to a value of 135% it rated current, it must trip within one hour.
If a circuit breaker is over loaded to a value of 200% it rated current, it must trip within two minutes.


Tripped Position

All circuit breakers do not trip to the center position. The following circuit breakers do not have a center position, and they trip to the "off" position: Cutler Hammer, Bryant and Murray.


Square D Circuit Breakers with Red Indicator Flags

For Maximum Resolution, Click on the Body of the Picture.

Thermal Oven Tests of Square D Circuit Breakers to 
				Determine the Temperature a 20 amp Breaker Trips at - 550 degrees Fahrenheit

Two Square D Circuit Breakers were placed in an Oven.
The Lens melted at 450°F; the Breaker Tripped at 550°F.

Sqaure D Circuit Breakers with Plastic Lens intact - Tripping was due to Electrical Activity

The Plastic Lenses are intact. The Circuit Breakers in this Panel
tripped because of Electrical Activity and not the Heat of the Fire.

Square D Circuit Breaker with Lenses begining to melt 
                    		- Tripped Circuit Breakers could be due to the temperature of the fire

The Plastic Lenses in this Panel are starting to melt.
The Heat of the Fire could have tripped the Circuit Breakers.

Exemplar Square D Circuit Breaker with Clear Plastic Back.

Exemplar Square D Circuit Breaker with Clear Plastic Back.


Cutler Hammer Circuit Breaker Overheating Due to a Loose Wire Connection

For Maximum Resolution, Click on the Body of the Picture.

When a tree limb fell, there was structural damage to this homeowner's weatherhead and meterbase. After repairs were made, the homeowner complained that his lights were blinking and the dryer circuit breaker was tripping. The inside electrical distribution panel was directly behind the meterbase. It is possible that when the weatherhead moved, it pulled the conductors feeding the inside panel box; it is also possible that this problem existed long before the tree limb fell.

A Loose Electrical Connection has Heated the Screw and Caused it to 
                      Oxidized or Rust

Heat on a Screw will cause it to Oxidize or Rust (F09-028).

The Heat produced by Loose Electrical Connection has Cracked the Wire Insulation 
                  and is starting to melt the aluminum conductor

The Heat from the Loose Electrical Connection has cracked the Wire
Insulation and the Aluminum Conductor is starting to melt (F09-028).

The Heat from the Loose Electrical Connection has Cracked 
                    and Discolored the Plastic Housing of the Circuit Breaker

The Plastic on the Bottom of the Circuit Breaker was Cracked
and Discolored (F09-028).


Square D - Circuit Breaker Damage Due to a Loose Connection at the Power Bus

For Maximum Resolution, Click on the Body of the Picture.

The day before this fire, the homeowner heard a cracking sound whenever the central air conditioning came on. The next day, a small fire occurred when an electrician was tightening the screws in the panel box.

There is no Damage to the Front of the Circuit Breakers in the 
                   Electrical Distribution Panel

Looking at the Front of the Electrical Distribution Panel,
there appeared to be no Damage (F09-045).

A Loose Circuit Breaker Connetion has melted part of the Power Bus and
                    the Power Clips of two Circuit Breakers

One of the Power Clips on the AC Circuit Breaker was Missing,
Part of the Power Bus was Missing and Melting of a Power Clip.

The Loose Circuit Breaker Connection has melted a section of the Panel Power Bus 
                       and there is arcing on the Power Bus Section Immediate below this

Missing Power Bus and Arcing on the Power Bus Immediately below
the Missing Bus (F09-045).

The Loose Circuit Breaker Connection Melted the Top Circuit Breaker Power Clip
                         and Damaged the Bottom Circuit Breaker Power Clip

Missing Top Power Clip and Melting on the Bottom Power Clip
of the AC Circuit Breaker (F09-045).

The Circuit Breaker Oppsite the Loose Connection 
                    also Suffered Damage (melting) to its Power Clip

The Circuit Breaker Across form the AC Circuit Breaker shared
the same Power Bus, and its Top Clip was melted (F09-045).


GE Circuit Breaker Overheating Due to Misaligned Contacts:

For Maximum Resolution, Click on the Body of the Picture.

A one-half size GE circuit breaker was repeatedly tripping at a RV hookup. The paper barcode on the circuit breaker had started to turn brown. The problem was traced to the contacts inside the circuit breaker being misaligned.

In the ON Position there is no continuity of the Circuit Breaker

No Continuity with GE Circuit Breaker in "ON" Position.

The Internal Heat from the Circuit Breaker has Turned the Paper Barcode Brown

Brown Area on Barcode Label Indicating Excessive Heat.

The Internal Heat in the Circuit Breaker was caused by the Contacts not being Aligned

GE Circuit Breaker with Cover Removed - Contacts Not Aligned.

Better View of Circuit Breaker Contacts not Aligned

Side View of GE Circuit Breaker with Misaligned Contacts.


Infamous Federal Pacific Electric Stab-Lok Circuit Breakers

For Maximum Resolution, Click on the Body of the Picture.

Almost every electrician I have talked with has had problems with Federal Pacific Electric (FPE) circuit breakers not tripping. In 1979, FPE was purchased by Reliance Electric Co., a subsidiary of Exxon Corporation. In June 1980, Reliance Electric informed the U.S. Consumer Product Safety Commission (CPSC) that many FPE circuit breakers did not fully comply with Underwriters Laboratories (UL) requirements. In 1983, the CPSC issued a letter concerning FPE circuit breakers and closed its investigation: http://www.cpsc.gov/cpscpub/prerel/prhtml83/83008.html or CPSC-FPE-Letter-83008.pdf . The US CPSC has not issued a recall on any FPE circuit breakers.

Federal Pacific Electric Panel Box - FPE Electrical Distribution Panel

Small FPE Panel Box with "Federal" on the Door.

Small FPE Panel Box without Cover

Small FPE Panel without Cover.

Full Size Federal Pacific Electric (FPE) Panel Box with Stab-Lok Circuit Breakers

Full Size FPE Panel Box with Stab-Lok Circuit Breakers (F08-020).

Single Pole, Double Pole and 3-Phase Federal Pacific Electric (FPE) Stab-Lok Circuit Breakers

Single Pole, Double Pole, and Three-Phase FPE Circuit Breakers (F08-020).

Two Federal Pacific Electric (FPE) Panel Boxes at a Commerical Location

Two FPE Panel Boxes at a Commercial Location (F08-020).

Closer View of Commercial Federal Pacific Electric (FPE) Panel Box

Closer View of Commercial FPE Panel Box (F08-020).

References: http://inspectapedia.com/fpe/fpe.htm"

FPE Circuit Breaker Fires

I have only had one fire that was caused by a FPE breaker failure, and it was not a Stab-Lok type. However, I have had numerous requests for the photographs: http://www.Electrical-Forensics.com/EDP/EDP-Fires.html .


 

Valid HTML 4.01 Transitional    Valid CSS!