Landis 3

What Did it Look Like Before the Fire?

DonanEngineering Fire Investigation, Residential & Commercial Structure Fires

What did it look like before the fire?  We all have seen the aftermath of an “electrical” fire and thought, “I wish I could have seen it before the fire.”  I have had that privilege.  In addition to being a fire investigator, I am an electrical inspector.

Photo 1

I have inspected over 3,000 installations and have seen many potential disasters.  I like to think that, as a result of the inspections, these disasters were prevented.

A typical single-wide mobile-home installation uses four conductors to supply the load center inside the home (Photograph 1).  Look closely at the black wire with the white stripe and the smaller green wire. Both of these wires were inside the PVC conduit that goes into the ground.  These wires should have been continuous to the breaker box.  Instead, the wires were only long enough to enter the conduit and give the appearance that they were connected at both ends.  The black wire with a white stripe is the grounded conductor, more commonly called the neutral.  This wire provides a return path for unbalanced current and establishes a reference point to ground.  When this wire is properly installed, the voltage between it and either of the two ungrounded or hot wires is 120 volts.  If not connected, the voltage will fluctuate depending on what load is being supplied.  Even though the voltage between the hot wires will remain 240 volts, the voltage between the neutral and one hot may be 140 volts, leaving the other neutral to hot at 100 volts.  When this occurs, the homeowner may notice a dimming of the lights when the refrigerator turns on, but might not be aware that the refrigerator compressor motor may be overheating.

Photo 2

If the green grounding wire would have been continuous and terminated at the ground bar attached to the breaker box enclosure, the ground wires of the individual circuits would be connected to the actual ground and would reduce the likelihood of personal injury or fire.  As it was, nothing inside the house would have been grounded.  If an energized wire were to contact a metal object, there would not be a low impedance path back to ground, and the overprotection device would not open the circuit.  One more item to note is the grounding electrode conductor, the small copper wire attached beside the green grounding wire, which the National Electric Code (NEC) requires to be connected to the grounded service conductor, not to the enclosure.[1]

Photo 3

This recessed ceiling light was discovered during a rewiring project (Photograph 2).  The connector used to protect the wire as it enters the junction box is missing.[2]  Four of these light fixtures were installed, and not one had a connector.  Also, these fixtures were not listed as type IC (the UL listing to allow for insulation to be placed in contact with the fixture).[3]  More noteworthy is the black, hot wire, which was pinched under the cover during installation.  Looking inside, the damage is more apparent (Photograph 3). If the right conditions were to exist, a fire could start in the attic of this house.

Photo 4

This last photograph is the end result of a “professional” bathroom remodel in which the new vent light was installed.  How many violations can you find? I see at least eight.

 

 

 

 

                                                                                                                               

[1] 250.24 Grounding Service-Supplied Alternating-Current Systems.

(A) System Grounding Connections. A premises wiring system supplied by a grounded ac service shall have a grounding electrode conductor connected to the grounded service conductor, at each service, in accordance with 250.24(A)(1) through (A)(5). NEC 2011.

[2] 410.116 Clearance and Installation.
(A) Clearance. (1) Non-Type IC. A recessed luminaire that is not identified for contact with insulation shall have all recessed parts spaced not less than 13 mm (1?2 in.) from combustible materials. The points of support and the trim finishing off the openings in the ceiling, wall, or other finished surface shall be permitted to be in contact with combustible materials.
(B) Installation. Thermal insulation shall not be installed above a recessed luminaire or within 75 mm (3 in.) of the recessed luminaire’s enclosure, wiring compartment, ballast, transformer, LED driver, or power supply unless the luminaire is identified as Type IC for insulation contact.

[3] 410.116 Clearance and Installation.
(A) Clearance. (1) Non-Type IC. A recessed luminaire that is not identified for contact with insulation shall have all recessed parts spaced not less than 13 mm (1?2 in.) from combustible materials. The points of support and the trim finishing off the openings in the ceiling, wall, or other finished surface shall be permitted to be in contact with combustible materials.
(B) Installation. Thermal insulation shall not be installed above a recessed luminaire or within 75 mm (3 in.) of the recessed luminaire’s enclosure, wiring compartment, ballast, transformer, LED driver, or power supply unless the luminaire is identified as Type IC for insulation contact.