Case of the Month: Faulty Electrical Work?

Jun 1, 2016 by

The house caught fire. After extinguishing the blaze, the fire department said the fire cause was a faulty electrical outlet. GEI was assigned to analyze the evidence and provide an opinion on the fire causation.

About five months earlier an electrical contractor added some extra electrical outlets to the house. Our expert ascertained which electrical codes were applicable, drove to the site, and inspected the area where the outside wall burned. The fire started in an open breezeway at the back of the residence.

Our expert then checked one of the new undamaged outlets, located on the living room wall, to see if it was properly installed. The steel box and the duplex receptacle were both properly grounded and the hot and neutral wires were connected to the correct terminals. It was a satisfactory installation.

201606one

 

A visit to the attic showed that the electrical wires from the fire damaged area went into a 5-inch square junction box mounted on the floor of the attic. The junction box also included other circuits as well as a duplex receptacle. It was apparent that the suspect outlet for the fire was connected to this existing branch circuit in the attic.

The remains of the burnt outlet box and its contents were previously removed and boxed for safe keeping of the evidence. The three wires were number 12 AWG copper, which was apparently part of a Romex cable.

201606two

The burnt outlet and several other outlets were installed by the contractor about five months before the fire. The plastic parts of the receptacle and the wire insulation were consumed in the fire, but there was still evidence that the ground wire was connected to both the steel box and the receptacle. However, the evidence showed that the contractor had used a standard duplex receptacle instead of a Ground Fault Circuit Interrupter (GFCI) receptacle. This was a violation of the Electrical Code, which required the use of GFCI receptacles in outside areas, which was clearly the case for the breezeway wall.

A GFCI receptacle has separate individual terminal screw connections for the “Line” and “Load” side for both the hot and neutral lines respectively. In contrast, a duplex receptacle has two terminal screw connections with a thin bridge of metal between them for both the hot and neutral side. The bridge of metal can be severed to allow each of the two (duplex) receptacles to be fed from separate power sources. This feature is commonly used in living areas where floor lamps can be controlled with wall switches. Photographs of the suspect burnt outlet clearly show the terminal screw arrangement used in a duplex receptacle.

The homeowners were unaware of any permit that the electrical contractor took out to perform the job of adding the outlets (receptacles) nor was there any line item on their bill showing the cost of an electrical permit. They also were not aware that a permit was required for this type of work. A permit is not required for certain types of minor repairs or upgrades such as the replacement of an existing duplex receptacle with a GFCI, or changing a light switch to a dimmer. In this case, the contractor added new circuits to existing branch circuits, which is the type of work that does requires a permit. It was the responsibility of the contractor to know these distinctions and to inform the homeowners.

The Electrical Code for this type of work also requires that an Arc Fault Circuit Interrupter (AFCI) be installed in any existing branch circuit when a new circuit extension is added. The Electrical Code specifies that a combination type AFCI breaker must be installed at the Main Panel to provide protection for the entire circuit. In addition, they require the same AFCI protection (at the Main Panel) for circuits which have GFCI receptacles. The logic here is that GFCI protects people from electrocution in certain wet areas but AFCI protects the whole house from fire.

A combination AFCI protects against both series and parallel types of arcs in the line, which may cause a fire. An arc is an electrical breakdown in the air and/or vaporized material, either insulation or metal. Series arcs are generally caused by poor connections (high resistance) at terminals and at junctions (wire nuts), as well as corroded and/or loose power plugs and receptacle contacts. Parallel arcs can occur between the hot and neutral (or ground) wires when the insulation has been compromised. These are generally caused by damage to the wire insulation from nails, cuts, staple pinching, etc. Parallel arcs are generally more likely to cause fires due the high voltages involved. The real danger here is that the currents involved in the arc may not be high enough to trip a conventional breaker. The AFCI is designed to detect the characteristics of low current arcs, as well as to trip in the event of an over current or a short circuit.

Our expert inspected the Main Panel. It was essentially filled with circuit breakers. There was evidence of at least two (ungrounded) “knob and tube” circuits, which dated to the house construction in 1947. An older version of Romex cable (with a smaller ground wire) was also found in the attic. It was obvious that the modern AFCI breakers would not work because they would be incompatible with the panel. This plethora of wire types is very typical of a home that is more than 50 years old.

The Electrical Code requires that only new circuit branches or extensions to old electrical branches need to be equipped with AFCI protection. It is obvious that for true fire prevention, a new panel should have been installed with AFCI protection for all of the circuits. This would not have required rewiring the whole house. In addition, an AFCI that tripped would draw attention to potentially hazardous conditions that could then be corrected before a fire occurred.

Given the extent of the fire damage, there was no direct evidence to prove in absolute terms that the suspect outlet was responsible for the fire. However, the contractor did not provide the proper AFCI protection against arc faults, as defined in the Code, for the new circuit extensions, nor did he provide the required GFCI receptacle at the breezeway location. The electrical contractor did the homeowners a grave disservice by not bringing these facts to their attention. Also the contractor’s choice to perform this work without a permit was a willful disregard of the law.

Related Posts

Share This