Evaluating Electrical Systems after a Fire by Steve Hamilton, P.E., CFEI

Receptacle exposed to smoke and water due to fire.

Receptacle exposed to smoke and water due to fire.

After a fire, damage assessments begin.  One aspect of assessment is the electrical system.  There may be direct damage to electrical wiring or devices, or indirect damage from heat, smoke or water (fire suppression).  It’s surprising how frequently I see cost estimates for repairs that fail to include replacing, or adequately repairing, equipment that has been exposed to smoke or water.

The National Electrical Manufacturers Association (NEMA) provides two standards that are helpful in determining how to evaluate electrical equipment after a fire:

  • GD 1-2016 Evaluating Water-Damaged Electrical Equipment
  • GD 2-2016 Evaluating Fire- and Heat-Damaged Electrical Equipment

Both standards provide tables of electrical equipment types along with recommendations to replace, or potentially recondition, after fire or water exposure.  Any reconditioning done must be only after contacting the manufacturer for their recommendations.  The National Electrical Code warns that some cleaning and lubricating compounds can cause severe deterioration.  The original manufacturer of the equipment can ensure that any reconditioning is done properly.

Following the tables in these NEMA standards are sections that provide a detail on each type of equipment and specific concerns.  Breakers that have electronic trip units, like Ground Fault Circuit Interrupters (GFCI) or Arc Fault Circuit Interrupters (AFCI), should be replaced if exposed to heat, smoke, fire or water, as their reliability cannot be ensured after exposure.  Among the potential issues:

  • Degradation of electrical insulation
  • Electrical contact surface degradation
  • Loss of lubrication
  • Contamination
    • Preventing smooth operation
    • Corroding metal surfaces
Typical residential wiring with corrosion after fire.

Typical residential wiring with corrosion after fire.

Receptacles, switches and dimmers should all be replaced if exposed to heat, smoke, fire or water.  Also, any lighting fixtures, ballast and LED drivers should be replaced.

Residential wiring is typically Non-Metallic (NM).  The wire insulation is polyvinyl chloride (PVC) with an outer jacket of nylon.  Paper fillers are built into the wire which can retain moisture when exposed to water from fire suppression.  NM type cable must be replaced if exposed to heat, smoke, fire or water.

Of course, the exposure of electrical equipment must be evaluated.  Simply because an electrical device was in a structure fire does not ensure that it was exposed to factors that could lead to degradation.

Don’t forget to consider the National Electrical Manufacturers Association (NEMA) standards when assessing damage due to fire.  Ignoring these standards could potentially lead to electrical failures and additional exposure to liability.

Please contact me to discuss any electrical engineering challenges you have.